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ICSE Class 10 Chemistry Question 3 of 19

Solved 2017 Question Paper ICSE Class 10 Chemistry — Question 9

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Question

Question 1(e)

State one relevant observation for each of the following reactions:

(i) Addition of ethyl alcohol to acetic acid in the presence of concentrated Sulphuric acid.

(ii) Action of dilute Hydrochloric acid on iron (II) sulphide.

(iii) Action of Sodium hydroxide solution on ferrous sulphate solution.

(iv) Burning of ammonia in air.

(v) Action of concentrated Sulphuric acid on hydrated copper sulphate.

Answer

(i) On warming, the mixture gives fruity smell. Acetic acid on heating with an alcohol and a dehydrating agent [conc. H2SO4] forms an ester — ethyl acetate.

C2H5OHethyl alcohol+CH3COOHacetic acid→Conc. H2SO4CH3−COO−C2H5ethyl ethanoate+H2O\underset{\text{ethyl alcohol}}{\text{C}_2\text{H}_5\text{OH}} + \underset{\text{acetic acid}}{\text{CH}_3\text{COOH}} \xrightarrow{\text{Conc. H}_2\text{SO}_4} \underset{\text{ethyl ethanoate}}{\text{CH}_3-\text{COO}-\text{C}_2\text{H}_5} + \text{H}_2\text{O}

(ii) H2S gas is evolved. It has a foul smell like rotten eggs.
FeS + 2HCl [g] ⟶ FeCl2 + H2S

(iii) A dirty green precipitate is formed which is insoluble in excess of sodium hydroxide solution.
FeSO4 + 2NaOH ⟶ Fe(OH)2↓ (dirty green ppt.) + Na2SO4

(iv) Ammonia burns in the atmosphere of excess oxygen with a green or greenish yellow flame, forming nitrogen and water vapour.
4NH3 + 3O2 ⟶ 2N2 + 6H2O

(v) The blue coloured hydrous copper sulphate changes to white anhydrous copper sulphate as the water of crystallization is removed.

CuSO4.5H2O→Conc. H2SO4CuSO4 [White Anhydrous]+5H2O\text{CuSO}_4\text{.5H}_2\text{O} \xrightarrow{\text{Conc. H}_2\text{SO}_4} \text{CuSO}_4 \text{ [White Anhydrous]} + 5\text{H}_2\text{O}