{"id":16625,"date":"2018-08-24T05:54:46","date_gmt":"2018-08-24T05:54:46","guid":{"rendered":"https:\/\/cbselibrary.com\/?p=16625"},"modified":"2020-12-03T16:57:33","modified_gmt":"2020-12-03T11:27:33","slug":"selina-icse-solutions-class-9-chemistry-language-chemistry","status":"publish","type":"post","link":"https:\/\/cbselibrary.com\/selina-icse-solutions-class-9-chemistry-language-chemistry\/","title":{"rendered":"Selina Concise Chemistry Class 9 ICSE Solutions The Language of Chemistry"},"content":{"rendered":"

Selina Concise Chemistry Class 9 ICSE Solutions The Language of Chemistry<\/span><\/h2>\n

ICSE Solutions<\/a>Selina ICSE Solutions<\/a><\/p>\n

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 9 Chemistry Chapter 1 Language of Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 9 with Free PDF download option. Selina Publishers Concise Chemistry for Class 9 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.<\/p>\n

Download Formulae Handbook For ICSE Class 9 and 10<\/a><\/p>\n

Selina ICSE Solutions for Class 9 Chemistry Chapter 4 The Language of Chemistry<\/strong><\/p>\n

Page No: 8<\/strong><\/span><\/p>\n

Question 1.
\nWhat is a symbol? What information does it convey?
\nSolution:
\n<\/strong><\/span>A symbol is the short form which stands for the atom of a specific element or the abbreviations used for the names of elements.<\/p>\n

    \n
  1. It represents a specific element.<\/li>\n
  2. It represents one atom of an element.<\/li>\n
  3. A symbol represents how many atoms are present in its one\u00a0gram\u00a0(gm) atom.<\/li>\n
  4. It represents the number of times an atom is heavier than one atomic mass unit (amu) taken as a standard.<\/li>\n<\/ol>\n
    Question 2
    \nWhy is the symbol S for\u00a0sulphur<\/span>, but Na for sodium and Si for silicon?
    \nSolution:
    \n<\/span>In most cases, the first letter of the name of the element is taken as the symbol for that element and written in capitals (e.g. for\u00a0sulphur<\/span>, we use the symbol S). In cases where the first letter has already been adopted, we use a symbol derived from the Latin name (e.g. for sodium\/Natrium<\/span>, we use the symbol Na). In some cases, we use the initial letter in capital together with a small letter from its name (e.g. for silicon, we use the symbol Si).<\/div>\n
    <\/div>\n
    Question 3.
    \nWrite the full form of IUPAC. Name the elements represented by the following symbols:
    \nAu, Pb, Sn, Hg
    \nSolution:
    \n<\/strong><\/span>The full form of IUPAC is International Union of Pure and Applied Chemistry.
    \nNames of the elements:
    \nAu – Gold
    \nPb – Lead
    \nSn – Tin
    \nHg – Mercury<\/div>\n
    <\/div>\n
    Question 4.
    \nIf the symbol for Cobalt,\u00a0Co,<\/span>\u00a0were written as CO, what would be wrong with it?
    \nSolution:
    \n<\/strong><\/span>Co stands for Cobalt. If we write CO, then it would mean that it is a compound containing two non-metal ions, i.e. carbon and oxygen, which forms carbon monoxide gas.<\/div>\n

    Question 5(d).
    \n2H2<\/sub>
    \nSolution:
    \n<\/strong><\/span>(a) H stands for one atom of hydrogen.
    \n(b) H2<\/sub>\u00a0stands for one molecule of hydrogen.
    \n(c) 2H stands for two atoms of hydrogen.<\/p>\n

    Question 6.
    \nWhat is meant by atomicity? Name the diatomic element.
    \nSolution:
    \n<\/strong><\/span>The number of atoms of an element that join together to form a molecule of that element is known as its atomicity. Diatomic molecules: H2<\/sub>, O2<\/sub>, N2<\/sub>, Cl2<\/sub><\/div>\n
    <\/div>\n
    Question 7(a).
    \nExplain the terms ‘valency<\/span>‘ and ‘variable\u00a0valency<\/span>‘.
    \nSolution:<\/span><\/div>\n
      \n
    1. Valency\u00a0of Na is +1 because it can lose one electron.<\/li>\n
    2. Valency\u00a0of O is -2 because it can accept two electrons.<\/li>\n<\/ol>\n

      Variable\u00a0valency:<\/strong> It is the combining capacity of an element in which the metal loses more electrons from a shell next to a valence shell in addition to electrons of the valence shell.<\/p>\n

      Question 7(b).
      \nHow are the elements with variable\u00a0valency<\/span>\u00a0named? Explain with an example.
      \nSolution:
      \n<\/strong><\/span>If an element exhibits two different positive\u00a0valencies, then<\/div>\n
        \n
      1. for the lower\u00a0valency, use the suffix -OUS at the end of the name of the metal<\/li>\n
      2. for\u00a0the higher\u00a0valency, use the suffix -IC at the end of the name of the metal.<\/li>\n<\/ol>\n

        Example:<\/strong><\/p>\n\n\n\n\n
        Element<\/td>\nLower\u00a0valency<\/td>\nHigher\u00a0valency<\/td>\n<\/tr>\n
        Ferrum\u00a0(Iron)<\/td>\nFerrous (Fe2+<\/sup>)<\/td>\nFerric (Fe3+<\/sup>)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Question 8.
        \nGive the formula and\u00a0valency\u00a0of:<\/p>\n

          \n
        1. aluminate\u00a0\u2026\u2026\u2026\u2026\u2026\u2026\u2026 .<\/li>\n
        2. chromate\u00a0\u2026\u2026\u2026\u2026.\u2026\u2026.. .<\/li>\n
        3. aluminium\u00a0\u2026\u2026\u2026\u2026\u2026\u2026. .<\/li>\n
        4. cupric\u00a0\u00a0\u2026\u2026\u2026\u2026\u2026\u2026\u2026 .<\/li>\n<\/ol>\n

          Solution:<\/span><\/p>\n\n\n\n\n\n\n\n
          <\/td>\nName<\/strong><\/td>\nFormula<\/strong><\/td>\nValency<\/strong><\/td>\n<\/tr>\n
          a.<\/td>\nAluminate<\/td>\nAlO2<\/sub><\/td>\n-2<\/td>\n<\/tr>\n
          b.<\/td>\nChromate<\/td>\nCrO4<\/sub><\/td>\n-2<\/td>\n<\/tr>\n
          c.<\/td>\nAluminium<\/td>\nAl<\/td>\n+3<\/td>\n<\/tr>\n
          d.<\/td>\nCupric<\/td>\nCu<\/td>\n+2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

          Question 9.b
          \nWhat is the significance of formula?
          \nSolution:
          \n<\/strong><\/span>Chemical formula: The chemical formula of a substance (element or compound) is a symbolic representation of the actual number of atoms present in one molecule of that substance.
          \nIt also indicates the fixed proportion by weight in which atoms combine.
          \nRules:
          \n<\/strong>(i) The positive and negative radicals are written side by side (+ve\u00a0first) with their charge as a superscript on the right side.
          \n(ii) Charges are then interchanged and written as a subscript.
          \n(iii) The final formula is written without the sign of charge, e.g. Hg2<\/sub>O<\/p>\n

            \n
          1. Hg1+<\/sup>O2-
            \n<\/sup><\/li>\n
          2. \"Selina<\/li>\n
          3. Hg2<\/sub>O<\/li>\n<\/ol>\n

            Question 10(a).
            \nWhat do you understand by the following terms?
            \nAcid radical
            \nSolution:
            \n<\/strong><\/span>Acid radical:<\/strong> The electronegative or negatively charged radical is called an acid radical.
            \nExamples:<\/strong>\u00a0<\/em>Cl<\/span>–<\/sup>, O2-<\/sup><\/p>\n

            Question 10(b).
            \nWhat do you understand by the following terms? Basic radical
            \nSolution:
            \n<\/strong><\/span>Basic radical:<\/strong> The electropositive or positively charged radical is called a basic radical.
            \nExamples:<\/strong>\u00a0<\/em>K+<\/sup>, Na+<\/sup><\/div>\n

            Question 11.<\/p>\n

            Match the following:<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
            Compound<\/b><\/strong><\/td>\nFormula<\/b><\/strong><\/td>\n<\/tr>\n
            (a) Boric acid<\/td>\n\u00a0i.\u00a0NaOH<\/td>\n<\/tr>\n
            (b) Phosphoric acid<\/td>\n\u00a0ii.\u00a0SiO2<\/sub><\/td>\n<\/tr>\n
            (c) Nitrous acid<\/td>\n\u00a0iii.\u00a0Na2<\/sub>CO3<\/sub><\/td>\n<\/tr>\n
            (d) Nitric acid<\/td>\n\u00a0iv.\u00a0KOH<\/td>\n<\/tr>\n
            (e) Sulphurous\u00a0acid<\/td>\n\u00a0v.\u00a0CaCO3<\/sub><\/td>\n<\/tr>\n
            (f) Sulphuric\u00a0acid<\/td>\n\u00a0vi.\u00a0NaHCO3<\/sub><\/td>\n<\/tr>\n
            (g) Hydrochloric acid<\/td>\n\u00a0vii.\u00a0H2<\/sub>S<\/td>\n<\/tr>\n
            (h) Silica (sand)<\/td>\n\u00a0viii.\u00a0H2<\/sub>O<\/td>\n<\/tr>\n
            (i) Caustic soda (sodium hydroxide)<\/td>\n\u00a0ix.\u00a0PH3<\/sub><\/td>\n<\/tr>\n
            (j) Caustic potash (potassium hydroxide)<\/td>\n\u00a0x.\u00a0CH4<\/sub><\/td>\n<\/tr>\n
            (k) Washing soda(sodium carbonate)<\/td>\n\u00a0xi.\u00a0NH3<\/sub><\/td>\n<\/tr>\n
            (l) Baking soda(sodium bicarbonate)<\/td>\n\u00a0xii.\u00a0HCl<\/td>\n<\/tr>\n
            (m) Lime stone.(calcium carbonate)<\/td>\n\u00a0xiii.\u00a0H2<\/sub>SO3<\/sub><\/td>\n<\/tr>\n
            (n) Water<\/td>\n\u00a0xiv.\u00a0HNO3<\/sub><\/td>\n<\/tr>\n
            (o) Hydrogen\u00a0sulphide<\/td>\n\u00a0xv.\u00a0HNO2<\/sub><\/td>\n<\/tr>\n
            (p) Ammonia<\/td>\n\u00a0xvi.\u00a0H3<\/sub>BO3<\/sub><\/td>\n<\/tr>\n
            (q) Phosphine<\/td>\n\u00a0xvii.\u00a0H3<\/sub>PO4<\/sub><\/td>\n<\/tr>\n
            (r) Methane<\/td>\n\u00a0xviii.\u00a0H2<\/sub>SO4<\/sub><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

            Solution:<\/span><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
            Compound<\/strong><\/b><\/td>\nFormula (Ans)<\/strong><\/b><\/td>\n<\/tr>\n
            (a) Boric acid<\/td>\nxvi. H3<\/sub>BO3<\/sub><\/td>\n<\/tr>\n
            (b) Phosphoric acid<\/td>\nxvii. H3<\/sub>PO4<\/sub><\/td>\n<\/tr>\n
            (c) Nitrous acid<\/td>\nxv. HNO2<\/sub><\/td>\n<\/tr>\n
            (d) Nitric acid<\/td>\nxiv. HNO3<\/sub><\/td>\n<\/tr>\n
            (e) Sulphurous\u00a0acid<\/td>\nxiii. H2<\/sub>SO3<\/sub><\/td>\n<\/tr>\n
            (f) Sulphuric\u00a0acid<\/td>\nxviii. H2<\/sub>SO4<\/sub><\/td>\n<\/tr>\n
            (g) (a) Hydrochloric acid<\/td>\nxii.\u00a0HCl<\/td>\n<\/tr>\n
            (h) Silica (sand)<\/td>\nii. SiO2<\/sub><\/td>\n<\/tr>\n
            (i) Caustic soda
            \n(sodium hydroxide)<\/td>\n            		i.\u00a0NaOH<\/td>\n<\/tr>\n
            (j) Caustic potash (potassium hydroxide)<\/td>\niv. KOH<\/td>\n<\/tr>\n
            \u00a0(k) Washing soda
            \n(sodium carbonate)<\/td>\n            		iii. Na2<\/sub>CO3<\/sub><\/td>\n<\/tr>\n
            \n

            \u00a0(l) Baking soda
            \n(sodium bicarbonate)<\/p>\n<\/td>\n

            		vi. NaHCO3<\/sub><\/td>\n<\/tr>\n
            \u00a0(m) Lime stone
            \n(calcium carbonate)<\/td>\n            		v. CaCO3<\/sub><\/td>\n<\/tr>\n
            (n) Water<\/td>\nviii. H2<\/sub>O<\/td>\n<\/tr>\n
            (o) Hydrogen\u00a0sulphide<\/td>\nvii. H2<\/sub>S<\/td>\n<\/tr>\n
            (p) Ammonia<\/td>\nxi. NH3<\/sub><\/td>\n<\/tr>\n
            (q) Phosphine<\/td>\nix. PH3<\/sub><\/td>\n<\/tr>\n
            (r) Methane<\/td>\nx. CH4<\/sub><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
            <\/div>\n
            \n

            Question 12.
            \nSelect the basic and acidic radicals in the following compounds.<\/p>\n

              \n
            1. MgSO4<\/sub><\/li>\n
            2. (NH4<\/sub>)2<\/sub>SO4<\/sub><\/li>\n
            3. Al2<\/sub>(SO4<\/sub>)3<\/sub><\/li>\n
            4. ZnCO3<\/sub><\/li>\n
            5. Mg(OH)2<\/sub><\/li>\n<\/ol>\n

              Solution:<\/span><\/p>\n<\/div>\n\n\n\n\n\n\n\n\n
              <\/td>\nAcidic radical<\/strong><\/td>\nBasic radical<\/strong><\/td>\n<\/tr>\n
              MgSO4<\/sub><\/td>\nSO4<\/sub>–<\/sup><\/td>\nMg+<\/sup><\/td>\n<\/tr>\n
              (NH4<\/sub>)2<\/sub>SO4<\/sub><\/td>\nSO4<\/sub>–<\/sup><\/td>\nNH4<\/sub>+<\/sup><\/td>\n<\/tr>\n
              Al2<\/sub>(SO4<\/sub>)3<\/sub><\/td>\nSO4<\/sub>–<\/sup><\/td>\nAl3+<\/sup><\/td>\n<\/tr>\n
              ZnCO3<\/sub><\/td>\nCO3<\/sub>–<\/sup><\/td>\nZn2+<\/sup><\/td>\n<\/tr>\n
              Mg(OH)2<\/sub><\/td>\nOH–<\/sup><\/td>\nMg2+<\/sup><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
              <\/div>\n
              Question 13.
              \nWrite chemical formula of the\u00a0sulphate<\/span>\u00a0of\u00a0Aluminium<\/span>, Ammonium and Zinc.
              \n<\/em>Solution:
              \n<\/strong><\/span>Valencies\u00a0of\u00a0aluminium, ammonium and zinc are 3, 1 and 2, respectively.
              \nThe\u00a0valency\u00a0of\u00a0sulphate\u00a0is 2.
              \nHence, chemical formulae of the\u00a0sulphates\u00a0of\u00a0aluminium, ammonium and zinc are\u00a0Al2<\/sub>(SO4<\/sub>)3<\/sub>, (NH4<\/sub>)2<\/sub>SO4\u00a0<\/sub>and ZnSO4<\/sub>.<\/div>\n
              <\/div>\n
              Question 14.
              \nThe\u00a0valency<\/span>\u00a0of an element\u00a0A\u00a0<\/em>is 3 and that of element\u00a0B\u00a0<\/em>is 2. Write the formula of the compound formed by the combination of\u00a0A\u00a0<\/em>and\u00a0B
              \nSolution:
              \n<\/strong><\/span>Formula of the compound = A2<\/sub>B3<\/sub><\/div>\n

              Question 15.
              \nWrite the chemical names of the following compounds:<\/p>\n

                \n
              1. Ca3<\/sub>(PO4<\/sub>)2<\/sub><\/li>\n
              2. K2<\/sub>CO3<\/sub><\/li>\n
              3. K2<\/sub>MnO4<\/sub><\/li>\n
              4. Mn3<\/sub>(BO3<\/sub>)2<\/sub><\/li>\n
              5. Mg(HCO3<\/sub>)2<\/sub><\/li>\n
              6. Na4<\/sub>Fe(CN)6<\/sub><\/li>\n
              7. Ba(ClO3<\/sub>)2<\/sub><\/li>\n
              8. Ag2<\/sub>SO3<\/sub><\/li>\n
              9. (CH3<\/sub>COO)2<\/sub>Pb<\/li>\n
              10. Na2<\/sub>SiO3<\/sub><\/li>\n<\/ol>\n

                Solution:
                \n<\/strong><\/span>Chemical names of compounds:<\/strong><\/p>\n

                  \n
                1. Ca3<\/sub>(PO4<\/sub>)2<\/sub>\u00a0– Calcium phosphate<\/li>\n
                2. K2<\/sub>CO3<\/sub>\u00a0– Potassium carbonate<\/li>\n
                3. K2<\/sub>MnO4\u00a0<\/sub>– Potassium\u00a0manganate<\/li>\n
                4. Mn3<\/sub>(BO3<\/sub>)2<\/sub>\u00a0– Manganese (II) borate<\/li>\n
                5. Mg(HCO3<\/sub>)2<\/sub>\u00a0– Magnesium hydrogen carbonate<\/li>\n
                6. Na4<\/sub>Fe(CN)6<\/sub>\u00a0– Sodium\u00a0ferrocyanide<\/li>\n
                7. Ba(ClO3<\/sub>)2<\/sub>\u00a0– Barium chlorate<\/li>\n
                8. Ag2<\/sub>SO3<\/sub>\u00a0– Silver\u00a0sulphite<\/li>\n
                9. (CH3<\/sub>COO)2<\/sub>Pb – Lead acetate<\/li>\n
                10. Na2<\/sub>SiO3<\/sub>\u00a0– Sodium silicate<\/li>\n<\/ol>\n

                  Question 16
                  \nWrite the basic radicals and acidic radicals of the following and\u00a0then write the chemical formulae of these compounds.<\/p>\n

                    \n
                  1. Barium\u00a0sulphate<\/li>\n
                  2. Bismuth nitrate<\/li>\n
                  3. Calcium bromide<\/li>\n
                  4. Ferrous\u00a0sulphide<\/li>\n
                  5. Chromium\u00a0sulphate<\/li>\n
                  6. Calcium silicate<\/li>\n
                  7. Potassium\u00a0ferrocyanide<\/li>\n
                  8. Stannic oxide<\/li>\n
                  9. Magnesium phosphate<\/li>\n
                  10. Sodium\u00a0zincate<\/li>\n
                  11. Stannic phosphate<\/li>\n
                  12. Sodium\u00a0thiosulphate<\/li>\n
                  13. Potassium\u00a0manganate<\/li>\n
                  14. Nickel bisulphate<\/li>\n<\/ol>\n

                    Solution:<\/span><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
                    Compounds<\/strong><\/b><\/td>\nAcidic
                    \n<\/strong><\/b>radical<\/strong><\/b><\/td>\n                    		Basic
                    \n<\/strong><\/b>radical<\/strong><\/b><\/td>\n                    		Chemical
                    \nformulae<\/strong><\/b><\/td>\n<\/tr>\n
                    Barium\u00a0sulphate<\/td>\nSO4<\/sub>2-<\/sup><\/td>\nBa2+<\/sup><\/td>\nBaSO4<\/sub><\/td>\n<\/tr>\n
                    Bismuth nitrate<\/td>\nNO3<\/sub>–<\/sup><\/td>\nBi3+<\/sup><\/td>\nBi(NO3<\/sub>)3<\/sub><\/td>\n<\/tr>\n
                    Calcium bromide<\/td>\nBr–<\/sup><\/td>\nCa2+<\/sup><\/td>\nCaBr2<\/sub><\/td>\n<\/tr>\n
                    Ferrous\u00a0sulphide<\/td>\nS2-<\/sup><\/td>\nFe2+<\/sup><\/td>\nFeS<\/td>\n<\/tr>\n
                    Chromium\u00a0sulphate<\/td>\nSO4<\/sub>2-<\/sup><\/td>\nCr3+<\/sup><\/td>\nCr2<\/sub>(SO4<\/sub>)3<\/sub><\/td>\n<\/tr>\n
                    Calcium silicate<\/td>\nSiO4<\/sub>2-<\/sup><\/td>\nCa2+<\/sup><\/td>\nCa2<\/sub>SiO4<\/sub><\/td>\n<\/tr>\n
                    Potassium\u00a0ferrocyanide<\/td>\n[Fe(CN)6<\/sub>]4-<\/sup><\/td>\nK1+<\/sup><\/td>\nK4<\/sub>[Fe(CN)6<\/sub>]<\/td>\n<\/tr>\n
                    Stannic oxide<\/td>\nO2-<\/sup><\/td>\nSn2+<\/sup><\/td>\nSnO2<\/sub><\/td>\n<\/tr>\n
                    Magnesium phosphate<\/td>\n(PO4<\/sub>)3-<\/sup><\/td>\nMg2+<\/sup><\/td>\nMg3<\/sub>(PO4<\/sub>)2<\/sub><\/td>\n<\/tr>\n
                    Sodium\u00a0zincate<\/td>\nZnO2-<\/sup><\/td>\nNa1+<\/sup><\/td>\nNa2<\/sub>ZnO2<\/sub><\/td>\n<\/tr>\n
                    \u00a0Stannic phosphate<\/td>\n(PO4<\/sub>)3-<\/sup><\/td>\nSn4+<\/sup><\/td>\nSn3<\/sub>(PO4<\/sub>)4<\/sub><\/td>\n<\/tr>\n
                    \u00a0Sodium\u00a0thiosulphate<\/td>\n(S2<\/sub>O3<\/sub>)2-<\/sup><\/td>\nNa1+<\/sup><\/td>\nNa2<\/sub>S2<\/sub>O3<\/sub><\/td>\n<\/tr>\n
                    Potassium\u00a0manganate<\/td>\nMnO4<\/sub>2-<\/sup><\/td>\nK1+<\/sup><\/td>\nK2<\/sub>MnO4<\/sub><\/td>\n<\/tr>\n
                    Nickel bisulphate<\/td>\nHSO4<\/sub>1-<\/sup><\/td>\nNi3+<\/sup><\/td>\nNi(HSO4<\/sub>)3<\/sub><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                    Question 16.
                    \nGive the names of the following compounds.<\/p>\n

                      \n
                    1. NaClO<\/li>\n
                    2. NaClO2<\/sub><\/li>\n
                    3. NaClO3<\/sub><\/li>\n
                    4. NaClO4<\/sub><\/li>\n<\/ol>\n

                      Solution:<\/span><\/p>\n

                        \n
                      1. NaClO\u00a0– Sodium hypochlorite<\/li>\n
                      2. NaClO2<\/sub>\u00a0– Sodium chlorite<\/li>\n
                      3. NaClO3<\/sub>\u00a0– Sodium chlorate<\/li>\n
                      4. NaClO4<\/sub>\u00a0– Sodium\u00a0perchlorate<\/li>\n<\/ol>\n

                        Question 18(a).
                        \nComplete the following statements by selecting the correct option :
                        \nThe formula of a compound represents
                        \ni. an atom
                        \nii. a particle
                        \niii. a molecule
                        \niv. a combination
                        \nSolution:
                        \n<\/strong><\/span>iii. The formula of a compound represents a molecule.<\/p>\n

                        Question 18(b).
                        \nComplete the following statements by selecting the correct option :
                        \nThe correct formula of\u00a0aluminium\u00a0oxide is
                        \ni. AlO3
                        \n<\/sub>ii. AlO2
                        \n<\/sub>\u00a0iii. Al2<\/sub>O3<\/sub>
                        \nSolution:
                        \n<\/strong><\/span>iii. The correct formula of\u00a0aluminium\u00a0oxide is Al2<\/sub>O3<\/sub>.<\/p>\n

                        Question 18(c).
                        \nComplete the following statements by selecting the correct option :
                        \nThe\u00a0valency\u00a0of nitrogen in nitrogen dioxide (NO2<\/sub>) is
                        \ni. one
                        \nii. two
                        \niii. three
                        \niv. four
                        \nSolution:
                        \n<\/strong><\/span>iv. The\u00a0valency<\/span>\u00a0of nitrogen in nitrogen dioxide (NO2<\/sub>) is four.<\/p>\n

                        Page No: 13<\/strong><\/span><\/p>\n

                        Question 1.
                        \nBalance the following\u00a0equations:<\/div>\n
                        \n
                          \n
                        1. Fe + H2<\/sub>O \u2192 Fe3<\/sub>O4<\/sub>\u00a0+ H2<\/sub><\/li>\n
                        2. Ca + N2<\/sub>\u00a0\u2192 Ca3<\/sub>N2<\/sub><\/li>\n
                        3. Zn + KOH \u2192 K2<\/sub>ZnO2<\/sub>\u00a0+ H2<\/sub><\/li>\n
                        4. Fe2<\/sub>O3<\/sub>\u00a0+ CO \u2192 Fe + CO2<\/sub><\/li>\n
                        5. PbO<\/span>\u00a0+ NH3<\/sub>\u00a0\u2192\u00a0Pb<\/span>\u00a0+ H2<\/sub>O + N2<\/sub><\/li>\n
                        6. Pb3<\/sub>O4<\/sub>\u00a0\u2192\u00a0PbO<\/span>\u00a0+ O2<\/sub><\/li>\n
                        7. PbS<\/span>\u00a0+ O2<\/sub>\u00a0\u2192\u00a0PbO<\/span>\u00a0+ SO2<\/sub><\/li>\n
                        8. S + H2<\/sub>SO4\u00a0<\/sub>\u2192 SO2<\/sub>\u00a0+ H2<\/sub>O<\/li>\n
                        9. S + HNO3<\/sub>\u00a0\u2192 H2<\/sub>SO4<\/sub>\u00a0+ NO2<\/sub>\u00a0+ H2<\/sub>O<\/li>\n
                        10. MnO2<\/sub>\u00a0+\u00a0HCl<\/span>\u00a0\u2192 MnCl2<\/sub>\u00a0+ H2<\/sub>O + Cl2<\/sub><\/li>\n
                        11. C + H2<\/sub>SO4<\/sub>\u00a0\u2192 CO2<\/sub>\u00a0+ H2<\/sub>O + SO2<\/sub><\/li>\n
                        12. KOH + Cl2<\/sub>\u00a0\u2192\u00a0KCl<\/span>\u00a0+\u00a0KClO<\/span>\u00a0+ H2<\/sub>O<\/li>\n
                        13. NO2<\/sub>\u00a0+H2<\/sub>O \u2192 HNO2<\/sub>\u00a0+ HNO3<\/sub><\/li>\n
                        14. \u00a0Pb3<\/sub>O4<\/sub>\u00a0+\u00a0HCl<\/span>\u00a0\u2192 PbCl2<\/sub>\u00a0+ H2<\/sub>O + Cl2<\/sub><\/li>\n
                        15. \u00a0H2<\/sub>O + Cl2<\/sub>\u00a0\u2192\u00a0HCl<\/span>\u00a0+ O2<\/sub><\/li>\n
                        16. \u00a0NaHCO3<\/sub>\u00a0\u2192 Na2<\/sub>CO3<\/sub>\u00a0+ H2<\/sub>O + CO2<\/sub><\/li>\n
                        17. HNO3<\/sub>\u00a0+ H2<\/sub>S \u2192 NO2<\/sub>\u00a0+ H2<\/sub>O + S<\/li>\n
                        18. P + HNO3<\/sub>\u00a0\u2192 NO2<\/sub>\u00a0+ H2<\/sub>O + H3<\/sub>PO4<\/sub><\/li>\n
                        19. Zn + HNO3<\/sub>\u00a0 \u2192 Zn(NO3<\/sub>)2<\/sub>\u00a0+ H2<\/sub>O + NO2<\/sub><\/li>\n<\/ol>\n<\/div>\n

                          Solution:
                          \n<\/strong><\/span>Balanced chemical equations:<\/p>\n

                            \n
                          1. 3Fe + 4H2<\/sub>O \u2192 Fe3<\/sub>O4<\/sub>\u00a0+ 4H2<\/sub><\/li>\n
                          2. 3Ca + N2<\/sub>\u00a0\u2192 Ca3<\/sub>N2<\/sub><\/li>\n
                          3. Zn + 2KOH \u2192 K2<\/sub>ZnO2<\/sub>\u00a0+ H2<\/sub><\/li>\n
                          4. Fe2<\/sub>O3<\/sub>\u00a0+ 3CO \u2192 2Fe + 3CO2<\/sub><\/li>\n
                          5. 3PbO + 2NH3<\/sub>\u00a0\u2192 3Pb + 3H2<\/sub>O + N2<\/sub><\/li>\n
                          6. 2Pb3<\/sub>O4<\/sub>\u00a0\u2192 6PbO + O2<\/sub><\/li>\n
                          7. 2PbS + 3O2<\/sub>\u00a0\u2192 2PbO + 2SO2<\/sub><\/li>\n
                          8. S + 2H2<\/sub>SO4\u00a0<\/sub>\u2192 3SO2<\/sub>\u00a0+ 2H2<\/sub>O<\/li>\n
                          9. S + 6HNO3<\/sub>\u00a0\u2192 H2<\/sub>SO4<\/sub>\u00a0+ 6NO2<\/sub>\u00a0+ 2H2<\/sub>O<\/li>\n
                          10. MnO2<\/sub>\u00a0+ 4HCl \u2192 MnCl2<\/sub>\u00a0+ 2H2<\/sub>O + Cl2<\/sub><\/li>\n
                          11. C + 2H2<\/sub>SO4<\/sub>\u00a0\u2192 CO2<\/sub>\u00a0+ H2<\/sub>O + SO2<\/sub><\/li>\n
                          12. 2KOH + Cl2<\/sub>\u00a0\u2192\u00a0KCl\u00a0+\u00a0KClO\u00a0+ H2<\/sub>O<\/li>\n
                          13. 2NO2<\/sub>\u00a0+ H2<\/sub>O \u2192 HNO2<\/sub>\u00a0+ HNO3<\/sub><\/li>\n
                          14. Pb3<\/sub>O4<\/sub>\u00a0+ 8HCl \u2192 3PbCl2<\/sub>\u00a0+ 4H2<\/sub>O + Cl2<\/sub><\/li>\n
                          15. 2H2<\/sub>O + 2Cl2<\/sub>\u00a0\u2192 4HCl + O2<\/sub><\/li>\n
                          16. 2NaHCO3<\/sub>\u00a0\u2192 Na2<\/sub>CO3<\/sub>\u00a0+ H2<\/sub>O + CO2<\/sub><\/li>\n
                          17. 2HNO3<\/sub>\u00a0+ H2<\/sub>S \u2192 2NO2<\/sub>\u00a0+ 2H2<\/sub>O + S<\/li>\n
                          18. P + 5HNO3<\/sub>\u00a0\u2192 5NO2<\/sub>\u00a0+ H2<\/sub>O + H3<\/sub>PO4<\/sub><\/li>\n
                          19. Zn + 4HNO3<\/sub>\u00a0 \u2192 Zn(NO3<\/sub>)2<\/sub>\u00a0+ 2H2<\/sub>O + 2NO2<\/sub><\/li>\n<\/ol>\n

                            Page No: 17
                            \n<\/strong><\/span><\/p>\n

                            Question 1.
                            \nFill in the blanks:<\/p>\n

                              \n
                            1. Dalton used symbol _____ for oxygen _____ for hydrogen.<\/li>\n
                            2. Symbol represents _____ atom(s) of an element.<\/li>\n
                            3. Symbolic expression for a molecule is called _____.\u00a0\u00a0.<\/li>\n
                            4. Sodium chloride has two radicals. Sodium is a _____ radical while chloride is _____ radical.<\/li>\n
                            5. Valency\u00a0of carbon in CH4<\/sub>\u00a0is _____ ,\u00a0in C2<\/sub>H6\u00a0<\/sub>_____, in C2<\/sub>H4<\/sub>\u00a0___ and in C2<\/sub>H2<\/sub>\u00a0is ____.<\/li>\n
                            6. Valency\u00a0of Iron in FeCl2<\/sub>\u00a0is _____\u00a0\u00a0and in FeCl3<\/sub>\u00a0it is ____ .<\/li>\n
                            7. Formula of iron (ill) carbonate is _____ .<\/li>\n<\/ol>\n

                              Solution:<\/span><\/p>\n

                                \n
                              1. Dalton used symbol [O]\u00a0for oxygen,[H]\u00a0for hydrogen.<\/li>\n
                              2. Symbol represents\u00a0gram\u00a0atom(s) of an element.<\/li>\n
                              3. Symbolic expression for a molecule is called\u00a0molecular formula.<\/li>\n
                              4. Sodium chloride has two radicals. Sodium is a\u00a0basic\u00a0radical, while chloride is an\u00a0acid\u00a0radical.<\/li>\n
                              5. Valency\u00a0of carbon in CH4<\/sub>\u00a0is\u00a04, in C2<\/sub>H6<\/sub>4, in C2<\/sub>H4<\/sub>4\u00a0and in C2<\/sub>H2<\/sub>\u00a0is\u00a04.<\/li>\n
                              6. Valency\u00a0of iron in FeCl2<\/sub>\u00a0is\u00a02\u00a0and in FeCl3<\/sub>\u00a0it is\u00a03.<\/li>\n
                              7. Formula of iron (III) carbonate is\u00a0Fe2<\/sub>[CO3<\/sub>]3<\/sub>.<\/li>\n<\/ol>\n

                                Question 2.
                                \nComplete the following table.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
                                 <\/p>\n

                                Acid\u00a0Radicals<\/p>\n

                                 <\/p>\n

                                Basic Radicals<\/td>\n

                                		Chloride<\/td>\nNitrate<\/td>\nSulphate<\/td>\nCarbonate<\/td>\nHydroxide<\/td>\nPhosphate<\/td>\n<\/tr>\n
                                Magnesium<\/td>\nMgCl2<\/sub><\/td>\nMg(NO3<\/sub>)2<\/sub><\/td>\nMgSO4<\/sub><\/td>\nMgCO3<\/sub><\/td>\nMg(OH)2<\/sub><\/td>\n\u00a0Mg3<\/sub>(PO4<\/sub>)2<\/sub><\/td>\n<\/tr>\n
                                Sodium<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
                                Zinc<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
                                Silver<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
                                Ammonium<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
                                Calcium<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
                                Iron (II)<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
                                Potassium<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                                Solution:<\/span><\/p>\n

                                \"Selina<\/p>\n

                                Question 3.
                                \nSodium chloride reacts with silver nitrate to produce silver chloride and sodium nitrate<\/p>\n

                                  \n
                                1. Write the equation.<\/li>\n
                                2. Check whether it is balanced, if not balance it.<\/li>\n
                                3. Find the weights of reactants and products.<\/li>\n
                                4. State the law which this equation satisfies.<\/li>\n<\/ol>\n

                                  Solution:
                                  \n<\/span>(a) NaCl+ AgNO3<\/sub>\u00a0\u2192 NaNO3<\/sub>\u00a0+\u00a0AgCl\u2193
                                  \n(b) It is a balanced equation.
                                  \n(c) Weights of reactants:NaCl\u00a0– 58.44, AgNO3<\/sub>\u00a0– 169.87
                                  \nWeights of products: NaNO3<\/sub>\u00a0– 84.99,\u00a0AgCl\u00a0– 143.32
                                  \nNaCl\u00a0+\u00a0AgNO3<\/sub>\u00a0\u2192\u00a0NaNO3\u00a0<\/sub>\u00a0+\u00a0AgCl
                                  \n(23+35.5) + (108+14+48) \u2192 (23+14+48) + (108+35.5)
                                  \n58.5\u00a0+\u00a0170\u00a0\u2192\u00a085 +\u00a0143.5
                                  \n228.5 g\u00a0\u2192\u00a0228.5 g
                                  \n(d) Law of conservation of mass: Matter is neither created nor destroyed in the course of a chemical reaction.<\/p>\n

                                  Question 4(a).
                                  \nWhat information does the following chemical equation convey? Zn\u00a0+\u00a0H2<\/sub>SO4<\/sub>\u00a0\u2192 ZnSO4<\/sub>+\u00a0H2
                                  \n<\/sub>Solution:<\/span>
                                  \n<\/strong>(a) This equation conveys the following information:<\/div>\n
                                    \n
                                  1. The actual result of a chemical change.<\/li>\n
                                  2. Substances take part in a reaction, and substances are formed as a result of the reaction.<\/li>\n
                                  3. Here, one molecule of zinc and one molecule of\u00a0sulphuric\u00a0acid react to give one molecule of zinc\u00a0sulphate\u00a0and one molecule of hydrogen.<\/li>\n
                                  4. Composition of respective molecules, i.e. one molecule of\u00a0sulphuric\u00a0acid contains two atoms of hydrogen, one atom of\u00a0sulphur\u00a0and four atoms of oxygen.<\/li>\n
                                  5. Relative molecular masses of different substances, i.e. molecular mass of
                                    \nZn = 65
                                    \nH2<\/sub>SO4<\/sub>\u00a0= (2+32+64) =\u00a098
                                    \nZnSO4\u00a0<\/sub>= (65+32+64) = 161
                                    \nH2<\/sub>\u00a0= 2<\/li>\n
                                  6. 22.4\u00a0litres\u00a0of hydrogen are formed at STP.<\/li>\n<\/ol>\n
                                    Question 4(b).
                                    \nWhat information do the following chemical equations convey? Mg\u00a0+\u00a02HCl \u2192 MgCl2<\/sub>+\u00a0H2
                                    \n<\/sub>Solution:<\/span>
                                    \n(b) This equation conveys the following information:<\/div>\n
                                      \n
                                    1. Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen gas.<\/li>\n
                                    2. 24 g of magnesium reacts with 2(1 + 35.5) = 73 g of hydrochloric acid to produce (24 + 71), i.e. 95 g of magnesium chloride.<\/li>\n
                                    3. Hydrogen produced at STP is 22.4\u00a0litres.<\/li>\n<\/ol>\n
                                      Question 5(a).
                                      \nWhat are polyatomic ions? Give two examples.
                                      \nSolution:
                                      \n<\/strong><\/span>(a)\u00a0A poly-atomic ion is a charged ion composed of two or more atoms covalently bounded that can be carbonate (CO3<\/sub>2-)\u00a0<\/sup>and\u00a0sulphate<\/span>\u00a0(SO4<\/sub>2-<\/sup>)<\/div>\n
                                      <\/div>\n
                                      Question 5(b).
                                      \nName the fundamental law that is involved in every equation.
                                      \nSolution:<\/span>
                                      \n(b) The fundamental laws which are involved in every equation are:<\/div>\n
                                        \n
                                      1. A chemical equation consists of formulae of reactants connected by plus sign (+) and arrow (\u2192) followed by the formulae of products connected by plus sign (+).<\/li>\n
                                      2. The sign of an arrow (\u2192) is to read ‘to form’. It also shows the direction in which reaction is predominant.<\/li>\n<\/ol>\n
                                        Question 6(a).
                                        \nWhat is the\u00a0valency<\/span>\u00a0of : fluorine in CaF2<\/sub>
                                        \nSolution:
                                        \n<\/span>(a) Valency<\/span>\u00a0of fluorine in\u00a0CaF2\u00a0<\/sub>is -1.<\/div>\n
                                        <\/div>\n
                                        \n
                                        Question 6(b).
                                        \nWhat is the\u00a0valency<\/span>\u00a0of :
                                        \nsulphur<\/span>\u00a0in SF6
                                        \n<\/sub>Solution:<\/span><\/div>\n<\/div>\n
                                        (b) Valency<\/span>\u00a0of\u00a0sulphur<\/span>\u00a0in SF6<\/sub>\u00a0is -6.<\/div>\n
                                        <\/div>\n
                                        \n

                                        Question 6(c).<\/p>\n

                                        What is the\u00a0valency<\/span>\u00a0of :<\/p>\n

                                        phosphorus in PH3<\/sub>
                                        \nSolution:
                                        \n<\/span>(c) Valency<\/span>\u00a0of phosphorus in PH3<\/sub>\u00a0is +3.<\/p>\n<\/div>\n

                                        Question 6(d).
                                        \nWhat is the\u00a0valency<\/span>\u00a0of : carbon in CH4<\/sub><\/div>\n
                                        Solution:<\/span><\/div>\n
                                        (d) Valency<\/span>\u00a0of carbon in CH4<\/sub>\u00a0is +4.<\/div>\n
                                        <\/div>\n
                                        Question 6(e).
                                        \nWhat is the\u00a0valency<\/span>\u00a0of :
                                        \nnitrogen in the following compounds:
                                        \n(i<\/span>)\u00a0N2<\/sub>O3<\/sub>\u00a0<\/i>(ii) N2<\/sub>O5<\/sub>\u00a0(iii) NO2<\/sub>\u00a0(iv) NO
                                        \nSolution:
                                        \n<\/span>(e) Valency\u00a0of nitrogen in the given compounds:<\/div>\n
                                          \n
                                        1. N2<\/sub>O3\u00a0<\/sub>\u00a0= N is +3<\/li>\n
                                        2. N2<\/sub>O5\u00a0<\/sub>= N is +5<\/li>\n
                                        3. NO2<\/sub>\u00a0= N is +4<\/li>\n
                                        4. NO\u00a0= N is +2<\/li>\n<\/ol>\n
                                          Question 7.
                                          \nWhy should an equation be balanced? Explain with the help of a simple equation.
                                          \nSolution:
                                          \n<\/strong><\/span>According to law of conservation of mass, “matter can neither be created nor be destroyed in a chemical reaction”. This is possible only, if total number of atoms on the reactants side is equals to total number of atoms on products side. Thus, a chemical reaction should be always balanced.
                                          \nLet us consider an example,
                                          \nFe\u00a0+\u00a0H2<\/sub>O\u00a0\u2192 Fe3<\/sub>O4<\/sub>\u00a0+\u00a0H2
                                          \n<\/sub>In this equation number of atoms on both sides is not the same, the equation is not balanced.
                                          \nThe balanced form of this equation is given by,
                                          \n3Fe\u00a0+\u00a04H2<\/sub>O \u00a0\u2192 Fe3<\/sub>O4<\/sub>\u00a0+\u00a04H2<\/sub><\/div>\n
                                          <\/div>\n
                                          Question 8(a).
                                          \nWrite the balanced chemical equations of the following reactions. sodium hydroxide\u00a0+\u00a0sulphuric\u00a0acid \u2192 sodium\u00a0sulphate\u00a0+\u00a0water
                                          \nSolution:
                                          \n<\/span>2NaOH + H2<\/sub>SO4<\/sub>\u00a0\u2192 Na2<\/sub>SO4<\/sub>\u00a0+ 2H2<\/sub>O<\/div>\n
                                          \n

                                          Question 8(b).
                                          \nWrite the balanced chemical equations of the following reactions. potassium bicarbonate\u00a0+\u00a0sulphuric\u00a0acid \u2192 potassium\u00a0sulphate\u00a0+\u00a0carbon dioxide\u00a0+\u00a0water
                                          \nSolution:
                                          \n<\/span>2KHCO3<\/sub>\u00a0+ H2<\/sub>SO4<\/sub>\u00a0\u2192 K2<\/sub>SO4<\/sub>\u00a0+ 2CO2<\/sub>\u00a0+ 2H2<\/sub>O<\/p>\n

                                          Question 8(c).
                                          \nWrite the balanced chemical equations of the following reactions.\u00a0iron\u00a0+\u00a0sulphuric\u00a0acid \u2192 ferrous\u00a0sulphate\u00a0+\u00a0hydrogen.
                                          \nSolution:
                                          \n<\/span>Fe + H2<\/sub>SO4<\/sub>\u00a0\u2192 FeSO4<\/sub>\u00a0+ H2<\/sub><\/p>\n

                                          Question 8(d).
                                          \nWrite the balanced chemical equations of the following reactions. chlorine\u00a0+\u00a0sulphur\u00a0dioxide\u00a0+\u00a0water \u2192\u00a0\u00a0sulphuric\u00a0acid\u00a0+\u00a0hydrogen chloride
                                          \nSolution:
                                          \n<\/span>Cl2<\/sub>\u00a0+ SO2<\/sub>\u00a0+ 2H2<\/sub>O \u2192 H2<\/sub>SO4<\/sub>\u00a0+ 2HCl<\/p>\n

                                          Question 8(e).
                                          \nWrite the balanced chemical equations of the following reactions. silver nitrate \u2192 silver\u00a0+\u00a0nitrogen dioxide\u00a0+\u00a0oxygen”
                                          \nSolution:
                                          \n<\/span>2AgNO3<\/sub>\u00a0\u2192 2Ag + 2NO2<\/sub>\u00a0+ O2<\/sub><\/p>\n

                                          Question 8(f).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \ncopper\u00a0+\u00a0nitric acid \u2192 copper nitrate\u00a0+\u00a0nitric oxide\u00a0+\u00a0water
                                          \nSolution:
                                          \n<\/span>3Cu + 8HNO3<\/sub>\u00a0\u2192 3Cu(NO3<\/sub>)2<\/sub>\u00a0+ 2NO +\u00a04H2<\/sub>O<\/p>\n

                                          Question 8(g).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \nammonia\u00a0+\u00a0oxygen \u2192 nitric oxide\u00a0+\u00a0water
                                          \nSolution:
                                          \n<\/span>\u00a0 \"Selina<\/p>\n

                                          Question 8(h).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \nbarium chloride\u00a0+\u00a0sulphuric\u00a0acid \u2192 barium\u00a0sulphate\u00a0+\u00a0hydrochloric acid
                                          \nSolution:
                                          \n<\/span>BaCl2<\/sub>\u00a0+ H2<\/sub>SO4<\/sub>\u00a0\u2192 BaSO4<\/sub>\u00a0+ 2HCl<\/p>\n

                                          Question 8(i).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \nzinc\u00a0sulphide\u00a0+\u00a0oxygen \u2192 zinc oxide\u00a0+\u00a0sulphur\u00a0dioxide
                                          \nSolution:
                                          \n<\/span>2ZnS + 3O2<\/sub>\u00a0\u2192 2ZnO + 2SO2<\/sub><\/p>\n

                                          Question 8(j).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \naluminium\u00a0carbide\u00a0+\u00a0water \u2192\u00a0aluminium\u00a0hydroxide\u00a0+\u00a0methane
                                          \nSolution:
                                          \n<\/span>Al4<\/sub>C3<\/sub>\u00a0+ 12H2<\/sub>O \u2192 4Al(OH)3<\/sub>\u00a0+ 3CH4<\/sub><\/p>\n

                                          Question 8(k).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \niron pyrites(FeS2<\/sub>)\u00a0+\u00a0oxygen\u00a0\u2192\u00a0ferric oxide\u00a0+\u00a0sulphur\u00a0dioxide
                                          \nSolution:
                                          \n<\/span>\u00a04FeS2<\/sub>\u00a0+ 11O2<\/sub>\u00a0\u2192 2Fe2<\/sub>O3<\/sub>\u00a0+ 8SO2<\/sub><\/p>\n

                                          Question 8(l).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \npotassium permanganate\u00a0+\u00a0hydrochloric acid\u00a0\u2192\u00a0potassium chloride\u00a0+\u00a0manganese chloride\u00a0+\u00a0chlorine\u00a0+\u00a0water
                                          \nSolution:
                                          \n<\/span>2KMnO4<\/sub>\u00a0+\u00a0HCl\u00a0\u2192 2KCl + 2MnCl2<\/sub>\u00a0+ 5Cl2<\/sub>\u00a0+ 8H2<\/sub>O<\/p>\n

                                          Question 8(m).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \naluminium\u00a0sulphate\u00a0+\u00a0sodium hydroxide \u2192 sodium\u00a0sulphate\u00a0+\u00a0sodium meta\u00a0aluminate\u00a0+\u00a0water.
                                          \nSolution:
                                          \n<\/span>Al2<\/sub>(SO4<\/sub>)3\u00a0<\/sub>+ 8NaOH \u2192 3Na2<\/sub>SO4<\/sub>\u00a0+ 2NaAlO2<\/sub>\u00a0+ 4H2<\/sub>O<\/p>\n

                                          Question 8(n).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \naluminium\u00a0+\u00a0sodium hydroxide\u00a0+\u00a0water \u2192 sodium meta\u00a0aluminate\u00a0+\u00a0hydrogen
                                          \nSolution:
                                          \n<\/span>2Al + 2NaOH + 2H2<\/sub>O \u2192 2NaAlO2<\/sub>\u00a0+ 3H2<\/sub><\/p>\n

                                          Question 8(o).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \npotassium\u00a0dichromate\u00a0+\u00a0sulphuric\u00a0acid \u2192 potassium\u00a0sulphate\u00a0+\u00a0chromium\u00a0sulphate\u00a0+\u00a0water\u00a0+\u00a0oxygen.
                                          \nSolution:
                                          \n<\/span>2K2<\/sub>Cr2<\/sub>O7<\/sub>\u00a0+ 8H2<\/sub>SO4<\/sub>\u00a0\u2192 2K2<\/sub>SO4<\/sub>\u00a0+ 2Cr2<\/sub>(SO4<\/sub>)3<\/sub>\u00a0+ 8H2<\/sub>O + 3O2<\/sub><\/p>\n

                                          Question 8(p).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \npotassium dichromate\u00a0+\u00a0hydrochloric acid\u00a0\u2192\u00a0Potassium chloride\u00a0+\u00a0chromium chloride\u00a0+\u00a0water\u00a0+\u00a0chlorine
                                          \nSolution:
                                          \n<\/span>K2<\/sub>Cr2<\/sub>O7<\/sub>\u00a0+ 14HCl \u2192 2KCl + 2CrCl3<\/sub>\u00a0+ 7H2<\/sub>O + 3Cl2<\/sub><\/p>\n

                                          Question 8(q).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \nsulphur\u00a0+\u00a0nitric acid \u2192\u00a0sulphuric\u00a0acid\u00a0+\u00a0nitrogen dioxide\u00a0+\u00a0water.
                                          \nSolution:
                                          \n<\/span>S + HNO3<\/sub>\u00a0\u2192 H2<\/sub>SO4<\/sub>\u00a0+ NO2<\/sub>\u00a0+ H2<\/sub>O<\/p>\n

                                          Question 8(r).
                                          \nWrite the balanced chemical equations of the following reactions.
                                          \nsodium\u00a0chloride\u00a0+\u00a0manganese dioxide\u00a0+\u00a0sulphuric\u00a0acid \u2192 sodium hydrogen\u00a0sulphate\u00a0\u00a0+\u00a0manganese\u00a0sulphate\u00a0+\u00a0water\u00a0+\u00a0chlorine.
                                          \nSolution:
                                          \n<\/span>2NaCl + MnO2<\/sub>\u00a0+ 3H2<\/sub>SO4<\/sub>\u00a0\u2192 2NaHSO4<\/sub>\u00a0+ MnSO4<\/sub>\u00a0+ 2H2<\/sub>O + Cl2<\/sub><\/p>\n<\/div>\n

                                          \n

                                          Question 9(a).
                                          \nDefine atomic mass unit.
                                          \nSolution:
                                          \n<\/span>Atomic mass unit (amu) is equal to one-twelfth the mass of an atom of carbon-12 (atomic mass of carbon taken as 12).<\/p>\n

                                          Question 9(b)(ii)
                                          \nCalculate the molecular mass of the following:
                                          \n(NH4<\/sub>)2<\/sub>CO3<\/sub>
                                          \nGiven atomic mass of Cu\u00a0=\u00a063\u00b75, H\u00a0=\u00a01, O=\u00a016, C\u00a0=\u00a012, N\u00a0=\u00a014, Mg\u00a0=\u00a024, S\u00a0=\u00a032
                                          \nSolution:
                                          \n<\/span>Molecular mass of\u00a0(NH4<\/sub>)2<\/sub>CO3
                                          \n<\/sub>= (2 \u00d7 14) + (8 \u00d7 1) + 12 + (3 \u00d7 16)
                                          \n= 28 + 8 + 12 + 48
                                          \n= 96<\/p>\n

                                          Question 9(b)(iii)
                                          \nCalculate the molecular mass of the following:
                                          \n(NH2<\/sub>)2<\/sub>CO
                                          \nGiven atomic mass of Cu\u00a0=\u00a063\u00b75, H\u00a0=\u00a01, O=\u00a016, C\u00a0=\u00a012, N\u00a0=\u00a014, Mg\u00a0=\u00a024, S\u00a0=\u00a032
                                          \nSolution:
                                          \n<\/span>Molecular mass of\u00a0(NH2<\/sub>)2<\/sub>CO
                                          \n= (14\u00a0\u00d7\u00a02) + (4 \u00d7 1) + 12 + 16
                                          \n= 28 + 4 + 12 + 16
                                          \n= 60<\/p>\n

                                          Question 9(b)(iv)
                                          \nCalculate the molecular mass of the following:
                                          \nMg3<\/sub>N2
                                          \n<\/sub>Given atomic mass of Cu\u00a0=\u00a063\u00b75, H\u00a0=\u00a01, O\u00a0=\u00a016, C\u00a0=\u00a012, N\u00a0=\u00a014, Mg\u00a0=\u00a024, S\u00a0=\u00a032
                                          \nSolution:
                                          \n<\/span>Molecular mass of Mg3<\/sub>N2
                                          \n<\/sub>= (3 \u00d7 24) + (2 \u00d7 14)
                                          \n= 72 + 28
                                          \n= 100<\/p>\n

                                          Question 10(a).
                                          \nChoose the correct answer from the options given below.
                                          \nModern atomic symbols are based on the method proposed by
                                          \ni. Bohr
                                          \nii. Dalton
                                          \niii. Berzelius
                                          \niv. Alchemist
                                          \nSolution:<\/span>
                                          \niii. Berzelius<\/p>\n

                                          Question 10(b).
                                          \nChoose the correct answer from the options given below.
                                          \nThe number of carbon atoms in a hydrogen carbonate radical is
                                          \ni. One
                                          \nii. Two
                                          \niii. Three
                                          \niv. Four
                                          \nSolution:<\/span>
                                          \nOne<\/p>\n

                                          Question 10(c).
                                          \nChoose the correct answer from the options given below.
                                          \nThe formula of iron (III)\u00a0sulphate\u00a0is
                                          \ni. Fe3<\/sub>SO4<\/sub>
                                          \nii. Fe(SO4<\/sub>)3
                                          \n<\/sub>iii. Fe2<\/sub>(SO4<\/sub>)3
                                          \n<\/sub>iv. FeSO4<\/sub>
                                          \nSolution:<\/span>
                                          \niii.\u00a0Fe2<\/sub>(SO4<\/sub>)3<\/sub><\/p>\n

                                          Question 10(d).
                                          \nChoose the correct answer from the options given below.
                                          \nIn water, the hydrogen-to-oxygen mass ratio is
                                          \ni. 1: 8
                                          \nii. 1: 16
                                          \niii. 1: 32
                                          \niv. 1: 64
                                          \nSolution:
                                          \n<\/span>i. 1:8<\/p>\n

                                          Question 10(e).
                                          \nChoose the correct answer from the options given below.
                                          \nThe formula of sodium carbonate is Na2<\/sub>CO3<\/sub>\u00a0and that of calcium hydrogen carbonate is
                                          \ni. CaHCO3
                                          \n<\/sub>ii. Ca(HCO3<\/sub>)2
                                          \n<\/sub>iii.\u00a0Ca2<\/sub>HCO3
                                          \n<\/sub>iv. Ca(HCO3<\/sub>)3
                                          \n<\/sub>Solution:
                                          \n<\/span>i. Ca(HCO3<\/sub>)2<\/sub><\/p>\n<\/div>\n

                                          Solution 11.
                                          \n<\/strong><\/span>(a) A molecular formula\u00a0represent\u00a0The Molecule of an element or of a Compound.
                                          \n(b) The molecular formula of water (H2<\/sub>O) represents 18 parts by mass of water.
                                          \n(c) A balanced equation obeys the law of conservation of mass wherever unbalanced equation does not obey this law.
                                          \n(d) CO and Co represent carbon-monoxide and cobalt respectively.<\/p>\n

                                          Solution 12.<\/span><\/p>\n

                                            \n
                                          1. Relative molecular mass of CHCl3
                                            \n= 12 + 1 + (3 \u00d7 35.5)
                                            \n= 12 + 1 + 106.5
                                            \n= 119.5<\/li>\n
                                          2. Relative molecular mass of (NH4)2 Cr2O7
                                            \n= (14 \u00d7 2) + (1\u00d7 8) + (52 \u00d7 2) + (16 \u00d7 7)
                                            \n= 28 + 8 + 104 + 112
                                            \n= 252<\/li>\n
                                          3. Relative molecular mass of CuSO4\u00b7 5H2O
                                            \n= 63.5 + 32 + (16 \u00d7 4) + 5(2 + 16)
                                            \n= 159.5 + 90
                                            \n= 249.5<\/li>\n
                                          4. Relative molecular mass of (NH4)2SO4
                                            \n= (2 \u00d7 14) + (8 \u00d7 1) + 32 + (4 \u00d7 16)
                                            \n= 28 + 8 + 32 + 64
                                            \n= 132<\/li>\n
                                          5. Relative molecular mass of CH3COONa
                                            \n= (12 \u00d7 2) + (1\u00d7 3) + (16 \u00d7 2) + 23
                                            \n= 24 + 3 + 32 + 23
                                            \n= 82<\/li>\n
                                          6. Potassium chlorate (KClO3)
                                            \n= 39.1+ 35.5 + (16 \u00d7 3)
                                            \n= 39.1+ 35.5 + 48
                                            \n= 122.6<\/li>\n
                                          7. Ammonium chloroplatinate (NH4)2PtCl6
                                            \n= (14 \u00d7 2) + (1 \u00d7 8) + 195.08 + (35.5 \u00d7 6)
                                            \n= 28 + 8 + 195.08 + 213
                                            \n= 444.08<\/li>\n<\/ol>\n

                                            Solution 13.<\/span><\/p>\n\n\n\n\n\n\n\n
                                            Compound<\/strong><\/b><\/td>\nEmpirical formula<\/strong><\/b><\/td>\n<\/tr>\n
                                            \n

                                            (a) Benzene (C6<\/sub>H6<\/sub>)<\/p>\n<\/td>\n

                                            		CH<\/td>\n<\/tr>\n
                                            \n

                                            Compound<\/strong><\/b>Empirical formula
                                            \n<\/strong><\/b>(b) Glucose (C6<\/sub>H12<\/sub>O6<\/sub>)<\/p>\n<\/td>\n

                                            		CH2<\/sub>O<\/td>\n<\/tr>\n
                                            \n

                                            Compound<\/strong><\/b>Empirical formula
                                            \n<\/strong><\/b>(c) Acetylene (C2<\/sub>H2<\/sub>)<\/p>\n<\/td>\n

                                            		CH<\/td>\n<\/tr>\n
                                            \n

                                            Compound<\/strong><\/b>Empirical formula
                                            \n<\/strong><\/b>(d) Acetic acid (CH3<\/sub>COOH)<\/p>\n<\/td>\n

                                            		CH2<\/sub>O<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                                            Solution 14.
                                            \n<\/strong><\/span>Relative molecular mass of\u00a0MgSO4<\/sub>\u00b77H2<\/sub>O
                                            \n=24 + 32 + (16 \u00d7 4) + 7(2 + 16)
                                            \n=24 + 32 + 64 + 126
                                            \n=246
                                            \n26 g of Epsom salt contains 126 g of water of\u00a0crystallisation.
                                            \nHence, 100 g of Epsom salt contains
                                            \n\"Selina
                                            \nThe % of H2<\/sub>O in\u00a0MgSO4<\/sub>\u00b77H2<\/sub>O = 51.2<\/p>\n

                                            Solution 15.
                                            \n<\/strong><\/span>(a)\u00a0 Relative molecular mass of\u00a0Ca(H2<\/sub>PO4<\/sub>)<\/strong>2<\/strong>
                                            \n<\/sub>= 40.07 + (1 \u00d7 4) + (30.9 \u00d7 2) + (16 \u00d7 8)
                                            \n= 40.07 + 4 + 61.8 + 128
                                            \n= 233.87
                                            \n233.87 g\u00a0Ca(H2<\/sub>PO4<\/sub>)2\u00a0<\/sub>contains 61.8 g P
                                            \nSo, 100 g\u00a0Ca(H2<\/sub>PO4<\/sub>)2\u00a0<\/sub>contains
                                            \n\"Selina
                                            \nThe % of P in\u00a0Ca(H2<\/sub>PO4<\/sub>)2<\/sub>\u00a0is 26.42%.
                                            \n(b)\u00a0Relative molecular mass of\u00a0Ca3<\/sub>(PO4<\/sub>)<\/strong>2<\/strong>
                                            \n<\/sub>= (40.07 \u00d7 3) + (30.9 \u00d7 2) + (16 \u00d7 8)
                                            \n= 120.21 + 61.8 + 128
                                            \n= 310.01
                                            \n310.01 g\u00a0Ca3<\/sub>(PO4<\/sub>)2\u00a0<\/sub>contains 61.8 g P
                                            \nSo, 100 g\u00a0Ca(H2<\/sub>PO4<\/sub>)2\u00a0<\/sub>contains
                                            \n(IMAGE)
                                            \nThe % of P in\u00a0Ca(H2<\/sub>PO4<\/sub>)2<\/sub>\u00a0is 19.93%.<\/p>\n

                                            Solution 16.
                                            \n<\/strong><\/span>Relative molecular mass of KClO3
                                            \n<\/sub>= 39.09 + 35.5 + (3 \u00d7 16)
                                            \n= 122.59 g
                                            \n\"Selina
                                            \nThe percentages of K,\u00a0Cl<\/span>\u00a0and O in KClO3<\/sub>\u00a0are 31.9%, 28.9% and 39.1%, respectively.<\/p>\n

                                            Solution 17.
                                            \n<\/strong><\/span>Relative\u00a0molecular mass of urea is<\/p>\n\n\n\n\n\n\n\n
                                            Element<\/strong><\/b><\/td>\nNo. of atoms<\/strong><\/b><\/td>\nAtomic mass<\/strong><\/b><\/td>\nTotal<\/strong><\/b><\/td>\n<\/tr>\n
                                            N<\/td>\n2<\/td>\n14<\/td>\n28<\/td>\n<\/tr>\n
                                            C<\/td>\n1<\/td>\n12<\/td>\n12<\/td>\n<\/tr>\n
                                            H<\/td>\n4<\/td>\n1<\/td>\n4<\/td>\n<\/tr>\n
                                            O<\/td>\n1<\/td>\n16<\/td>\n16<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                                            [12 + 16 + 28 + 4] = 60
                                            \nHence, relative molecular mass of urea = 60
                                            \n\"Selina<\/p>\n

                                            More Resources for Selina Concise Class 9 ICSE Solutions<\/strong><\/p>\n