\nStrong acid<\/td>\n | Hydrochloric acid, HCl<\/td>\n | H+<\/sup>, Cl–<\/sup><\/td>\n<\/tr>\n\nNitric acid, HNO3<\/sub><\/td>\nH+<\/sup>, NO3<\/sub>–<\/sup><\/td>\n<\/tr>\n\nSulphuric acid, H2<\/sub>S04<\/sub><\/td>\nH+<\/sup>, HSO4<\/sub>–<\/sup>, SO4<\/sub>2-<\/sup><\/td>\n<\/tr>\n\nWeak acid<\/td>\n | Carbonic acid, H2<\/sub>C03<\/sub><\/td>\nH+<\/sup>, HCO3<\/sub>–<\/sup>, CO3<\/sub>2-<\/sup>, H2<\/sub>CO3<\/sub><\/td>\n<\/tr>\n\nEthanoic acid, CH3<\/sub>COOH<\/td>\nH+<\/sup>, CH3<\/sub>COO–<\/sup>, CH3<\/sub>COOH<\/td>\n<\/tr>\n\nSulphurous acid, H2<\/sub>SO3<\/sub><\/td>\nH+<\/sup>, HSO3<\/sub>–<\/sup>, SO3<\/sub>2-<\/sup>, H2<\/sub>SO3<\/sub><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/li>\nStrong acid and weak acid are defined as follows. \nA strong acid<\/strong> is completely ionised in water to produce a high concentration of hydrogen ions. \nA\u00a0weak acid<\/strong> is partially ionised in water to produce a low concentration of hydrogen ions.<\/li>\nThe pH of an acid solution changes with concentration of the acid. The concentration of the acid affects the concentration of hydrogen ions produced. For example: \n10 mol dm-3<\/sup> hydrochloric acid: pH = 1 \n01 mol dm-3<\/sup> hydrochloric acid: pH = 2<\/li>\npH values can be used to compare the acid strength of different acids. All the acids to be compared must be of the same concentration<\/strong>. \nFor example: \n10 mol dm-3<\/sup>hydrochloric acid: pH = 1 \n10 mol dm-3<\/sup> ethanoic acid: pH = 3<\/li>\nFor two different acids of the same concentration<\/strong>, the acid with the lower pH value <\/strong>is the stronger acid<\/strong>, i.e. higher degree of ionisation in water.<\/li>\n<\/ul>\nStrong and weak alkalis<\/strong><\/h2>\n\n- Sodium hydroxide is a strong alkali. It ionises fully when dissolved in water.
\n<\/li>\n - A strong alkali<\/strong> is an alkali which is fully ionised<\/strong> in water to produce a high concentration of hydroxide ions.<\/li>\n
- A weak alkali<\/strong> is an alkali which ionises partially<\/strong> in water to produce a low concentration of hydroxide ions.<\/li>\n
- Ammonia is an example of a weak alkali. It is only partly ionised in water, which means the ionisation of ammonia in water is incomplete. Only a small amount of ammonia molecules are ionised in water to produce ammonium ions and hydroxide ions.
\n<\/li>\n - Examples of strong and weak alkalis are shown in Table.
\n\n\n\nAlkali<\/strong><\/td>\nName<\/strong><\/td>\nParticles<\/strong><\/td>\n<\/tr>\n\nStrong alkali<\/td>\n | Sodium hydroxide, NaOH<\/td>\n | Na+<\/sup>, OH–<\/sup><\/td>\n<\/tr>\n\nPotassium hydroxide, KOH<\/td>\n | K+<\/sup>, OH–<\/sup><\/td>\n<\/tr>\n\nBarium hydroxide, Ba(OH)2<\/sub><\/td>\nBa2+<\/sup>,\u00a0OH–<\/sup><\/td>\n<\/tr>\n\nWeak alkali<\/td>\n | Ammonia, NH3<\/sub><\/td>\nNH3<\/sub>, NH4<\/sub>+<\/sup>,\u00a0OH–<\/sup><\/td>\n<\/tr>\n\nMethylamine, CH3<\/sub>NH2<\/sub><\/td>\nCH3<\/sub>NH2<\/sub>, CH3<\/sub>NH3<\/sub>+<\/sup>, OH–<\/sup><\/td>\n<\/tr>\n\nHydrazine, N2<\/sub>H4<\/sub><\/td>\nN2<\/sub>H4<\/sub>, N2<\/sub>H5<\/sub>+<\/sup>, OH–<\/sup><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/li>\n- Strong alkali and weak alkali are defined as follows.
\nA strong alkali<\/strong> is completely ionised in water to produce a high concentration of hydroxide ions. \nA weak alkali<\/strong> is partially ionisesed in water to produce a low concentration of hydroxide ions.<\/li>\n- The pH of an alkali solution changes with concentration of the alkali. The concentration of the alkali affects the concentration of hydroxide ions produced.
\nFor example: \n10 mol dm-3<\/sup>m-3<\/sup> sodium hydroxide solution pH = 13 \n01 mol dm-3<\/sup> sodium hydroxide solution pH = 12<\/li>\n- pH values can be used to compare the strength of different alkalis. All the alkalis to be compared must be of the same concentration<\/strong>. For example:
\n10 mol dm-3<\/sup> sodium hydroxide: pH = 13 \n10 mol dm-3<\/sup> ammonia solution: pH = 11<\/li>\n- For two different alkalis of the same concentration<\/strong>, the alkali with the higher pH value<\/strong> is the stronger alkali<\/strong>, i.e. higher degree of ionisation in water.<\/li>\n<\/ul>\n
<\/p>\n","protected":false},"excerpt":{"rendered":" How can we measure the strength of acids and alkalis? An acid produces hydrogen ions in aqueous solution. The acidity of a solution is a measure of the concentration of the hydrogen ions in the solution. A base produces hydroxide ions in aqueous solution. The alkalinity of a solution is a measure of the concentration … | | | | | | | | | | | | | | | | | | | | | | | |