Chemical Properties

Properties and Uses of Ethanol

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Properties and Uses of Ethanol

Physical Properties of Ethanol :
(i)   Pure ethanol is a colourless liquid.
(ii)  It has a specific smell and burning taste
(iii) Its boiling point is 351 K which is higher than corresponding alkanes
(iv) It is soluble in water. i.e., it is miscible with water in all proportions.

Chemical properties of Ethanol :
(i)   Dehydration : Ethanol. when heated with Conc. H2SO4 at 443 K or Al2O3 at 623 K undergoes dehydration, i.e. loses water molecule to from alkene.
Properties and Uses of Ethanol 1
(ii)  Reaction with Sodium : Alcohols are very weakly acidic. Ethanol reacts with sodium metal to form sodium ethoxide and hydrogen gas.
Properties and Uses of Ethanol 2
(iii) Oxidation with Chromic anhydride (CrO3) :
Properties and Uses of Ethanol 3
(iv) Oxidation with alkaline KMnO4 :
Properties and Uses of Ethanol 4
(v)  Oxidation with acidified Potassium dichromate : Ethanol is oxidized to ethanoic acid with the help of acidified K2Cr2O7
Properties and Uses of Ethanol 5
During this reaction, orange colour of K2Cr2O7 changes to green. Therefore, this reaction can be used for the identification of alcohols.
(vi) Esterification : Ethanol reacts with ethanoic acid in presence of concentrated H2SO4 to form ethyl ethanoate and water. The compound formed by the reaction of an alcohol with carboxylic acid is known as ester and the reaction is called Esterification. Esters are sweet fruity smelling compounds because they occur in fruits. They are used in ice creams, cold drinks and perfumes. The reaction takes place as follows.
Properties and Uses of Ethanol 6
Conc. H2SO4 acts as dehydrating agent, i.e., it removes water formed otherwise ester formed will get hydrolysed.
(vii) Ethanol is highly inflammable liquid i.e., it catches fire very easily. It burns with blue flame in presence of oxygen to form carbon dioxide and water.
Properties and Uses of Ethanol 7

What is the use of ethanol?

Uses of Ethanol :
(i)   Ethanol is present in alcoholic beverages such as beer, wine, whisky.
(ii)  Ethanol is used as antiseptic for sterilising wounds.
(iii) Ethanol is used incough syrups. digestive syrups and tonics.
(iv) Ethanol is being mixed with petrol and is used as motor fuel. This mixture is called power alcohol.
(v)  A mixture of ethanol and water has lower freezing point than water. This mixture is known as antifreeze and is used in radiators of vehicles in cold countries and at hill stations.
(vi) Ethanol is used for preparation of chloroform, iodoform, ethanoic acid, ethanal, ethyl ethanoate etc.
(vii) Ethyl alcohol is used as hypnotic (induces sleep).

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Properties and Uses of Ethanoic Acid

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Properties and Uses of Ethanoic Acid

Ethanoic acid (Acetic acid) CH3COOH : Ethanoic acid is most commonly known as acetic acid. Its dilute solution in water (5-8%) is known as vinegar, which is used for preserving food-sausage, pickles etc.

Physical properties :
(i)   Ethanoic acid is vinegar smelling liquid. The lower carboxylic acids are liquids whereas higher ones are solids.
(ii)  Ethanoic acid is sour in taste. Other lower carboxylic acids are also sour in taste.
(iii) Ethanoic acid has boiling point 391 K. Carboxylic acids have higher boiling points than corresponding alcohols, aldehydes and ketones.
(iv) Acetic acid is soluble in water, i.e., it is miscible with water in all proportions. The lower carboxylic acids are soluble in water but solubility in water decreases with increase in molecular weight.
(v)  Acetic acid freezes at 290 K. Thus, in cold weather crystallization of acetic acid may take place that is why pure acetic acid is called glacial acetic acid.

Chemical Properties :
(i)   Ethanoic acid is weak acid but it turns blue litmus red.
(ii)  Reaction with Metal. Ethanoic acid reacts with metals like Na, K, Zn etc. to form metal ethanoates and hydrogen gas.
Properties and Uses of Ethanoic Acid 1
(iii) Reaction with Carbonates. Ethanoic acid reacts with bicarbonates and carbonates and produces brisk effervescence due to formation of carbon dioxide.
Properties and Uses of Ethanoic Acid 2
(iv) Reaction with Base. Ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and water.
Properties and Uses of Ethanoic Acid 3
(v)  Decarboxylation (Removal of CO2). When sodium salt of ethanoic acid, i.e., sodium ethanoate is heated with soda lime (3 parts of NaOH and 1 part of CaO), methane gas is formed.
Properties and Uses of Ethanoic Acid 4
This reaction is known as decarboxylation because a molecule of CO2 is removed from a molecule of acid.
(vi) Reaction with alcohols. Ethanoic acid reacts with ethanol in presence of concentrated sulphuric acid to form esters which are pleasant fruity smelling compounds.
Properties and Uses of Ethanoic Acid 5
(vii) Reduction. Acetic acid, on reduction with lithium aluminium hydride, results in formation of ethanal, which on further reduction gives ethanol.
Properties and Uses of Ethanoic Acid 6

Uses of Ethanoic acid :
(i)   It is used for making vinegar
(ii)  It is used as a laboratory reagent
(iii) It is used for preparation of white lead [2PbCO3.Pb(OH)2] which is used in white paints.
(iv) It is used for coagulation of rubber from latex and casein (protein) from milk
(v)  It is used in preparation of acetone, ethyl acetate, acetic anhydride, aspirin which is used in medicines.
(vi) It is used in preparation of cellulose acetate which is used for making photographic film.
(vii) Its esters are used in artificial flavours in perfumes.
(viii) Its 5% solution is bactericidal (destroys bacteria)
(ix) Its compound basic copper acetate (verdigris) is used as green pigment.
(x) Aluminium acetate and chromium acetate are used as mordants in dyeing and waterproofing of fabrics.

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Chemical Properties of Carbon Compounds

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Chemical Properties of Carbon Compounds

Though we have millions of organic compounds, the reactions they undergo are limited. Some important reactions among them are discussed here.
They are:
1) Combustion reactions
2) Oxidation reactions
3) Addition reactions
4) Substitution reactions

1. Combustion reactions
Carbon, and its compounds burn in presence of oxygen or air to give CO2, heat and light.
The process of burning of carbon or carbon compound in excess of oxygen to give heat and light is called the combustion reaction. In the reactions carbon is in its maximum oxidation state of 4+ in the product.
Eg: 1) C + O2  →  CO2 + Energy
2) 2C2H6 + 7O2  →  4CO2 + 6H2O + Energy
3) CH3CH2OH + 3O2  →  CO2 + 3H2O + Energy
Generally, saturated hydrocarbons burn with a clear light blue flame, whereas unsaturated hydrocarbons burn with yellow flame with soot(carbon). If air is not sufficiently available during combustion, even saturated hydrocarbons give sooty flame. When Coal, Petroleum etc., burn in air they give oxides of sulphur and nitrogen in addition to CO2 and H2O which pollute the environment. When Coal or Charcoal is burnt sometimes they just glow red without flame. This is because to get a flame gaseous
fuels should burn.
Most of the aromatic compounds burn with sooty flame.
Because of the inlets of air getting closed, the fuel gases donot completely undergo combustion. Hence, it forms a sooty carbon form which gets coated over the vessels.A combustion reaction is generally defined as any reaction that sustains a flame. It usually involves burning with oxygen, though some exceptions
are there, combustion reaction is always exothermic, that is energy is liberated during combustion reaction.

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2. Oxidation reactions
Though combustion is generally oxidation reaction, all oxidation reactions are not combustion reactions. Oxidation reactions may be carried out using oxidizing agents. Oxidizing agents or Oxidants are substances that oxidize other substances. They themselves undergo reduction.
Eg: Alkaline Potassium permanganate or Acidified Potassium dichromate in solutions act as oxidizing agents and supplies oxygen to convert alcohols into carboxylic acids. Ethyl alcohol undergoes oxidation to form the product Acetaldehyde and finally Acetic acid.(see following equation).
Chemical Properties of Carbon Compounds 1

3. Addition reactions
Unsaturated organic compounds that contain multiple bonds (=, ≡ bonds) like alkenes and alkynes undergo addition reactions to become saturated. During the reactions addition of the reagent takes place at the double bonded or triple bonded carbon atoms.
Chemical Properties of Carbon Compounds 2
In the above reactions ‘Ni’ acts as ‘catalyst.’
Catalyst: A catalyst is a substance which regulates (increase/decrease) the rate of a given reaction without itself finally undergoing any chemical change.
These reactions are commonly used in the hydrogenation of vegetable oils using nickel as catalyst. Vegetable oils generally have long unsaturated carbon chains, while animal fats have saturated carbon chains.
Fats and oils are both of fatty acids. Oils are generally liquids at room temperature due to unsaturated fatty acids but fats are solids due to saturated fatty acids.

4. Substitution reactions
A reaction in which an atom or a group of atoms in a given compound is replaced by other atom or group of atoms is called a substitution reaction.
Alkanes, the saturated hydrocarbons are chemically least reactive.
Therefore they are also called paraffins (parum = little; affins = affinity,  i.e., no affinity towards chemical changes). However they undergo some chemical changes under suitable conditions which are substitution reactions.
For example, methane (CH4) reacts with chlorine in the presence of sunlight. Hydrogen atoms of CH4 are replaced by chlorine atoms.
Chemical Properties of Carbon Compounds 3

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