a) When carbon dioxide is passed through the calcium hydroxide solution, it turns milky due to the formation of insoluble calcium carbonate.
b) Reaction in Test tube A:
\(\underset{Acetic\ or\ ethnoic\ acid}{2CH_3COOH(1)}+\underset{Sodium\ carbonate}{Na_2CO_3(s)}\rightarrow\underset{Sodium\ acetate}{2CH_3COONa}+\underset{Water}{H_2O}+\underset{Carbon\ ioxide}{CO_2(g)}\)
Reaction in Test tube B:
\(\underset{Calciumhydroxide\\ (Lime\ water)}{Ca(OH)_2(aq)}+\underset{Carbondioxide}{CO_2(g)}\rightarrow\underset{Calcium\ carbonate\\ (White\ ppt)}{CaCO_3(s)\downarrow}\underset{Water}{H_2O}\)
c) No with ethanol no reaction takes place.
d) When a quick lime i.e., calcium oxide is added to water in a test tube, it forms calcium hydroxide which is lime water. This solution is filtered and the clear solution is obtained
\(CaO(s)+H_2O(l)\rightarrow Ca(OH)_2\)

i) Since compound C on combustion forms two moles of CO₂ and 3 moles of H₂ O, therefore compound C must contain two carbon atoms and six hydrogen atmos. Thus compound C must be C₂H₆ (ethane)
\(\underset{Ethene(C)}{2C_2H_6}+\underset{Oxygen}{7O_2}\xrightarrow{Heat}\underset{Carbon\ dioxide}{4CO_2}+\underset{Water}{6H_2O}\)
ii) Since compound (C) is obtained by addition of 1 mole of H₂ in presence of Ni to compound (B), therefore (B) must be ethane.
\(\underset{Ethene(B)}{CH2}=CH_2+H_2\xrightarrow{Ni/Heat}\underset{Ethene(C)}{CH_3-CH_3}\)
iii) Since compound (B) is formed by heating compound (A) with cone. H₂SO₄ therefore compound (A) must be ethanol.
\(\underset{Ethanol(A)}{CH_3CH_2OH}\xrightarrow{Conc. H_2SO_4,443K}CH_2=CH_2+\underset{Ethene(B)}{H_2O}\)

a)\(\underset{Ethanol}{CH_3CH_2OH}\xrightarrow{Conc.H_2SO_4.170^0C}CH_2=\underset{Ethene}{CH_2}+H_2O\)
b)\(\underset{Propanol}{CH_3CH_2CH_2OH+2[O]}\xrightarrow[or\ Aci.K_2Cr_2O_7,\Delta]{AlK.KMnO_4, \Delta}\underset{Propanoic\ acid}{CH_3CH_2COOH}+H_2O\)

Compound with molecular formula C₂H₄O₂ should be Ethanoic acid reacts with Na metal to give sodium ethanoate.
\(\underset{\underset{Ethanoic\ acid}{(C)}}{2CH_3COOH}+2Na\rightarrow\underset{\underset{Sodium\ ethanoate}{(R)}}{2CH_3COONa}+H_2\)
\(\underset{\underset{Ethanoic\ acid}{(C)}}{CH_3COOH}+\underset{\underset{methanol}{(A)}}{CH_3OH}\xrightarrow{conc. H_2SO_4}\underset{\underset{Methyl\ acetate}{(S)}}{CH_3COOCH_3+H_2O}\)
\(CH_3COOH+\underset{Sodium\\ hydroxide}{NAOH}\rightarrow\underset{\underset{Sodium\ ethanoate}{(R)}}{CH_3COONa}+H_2O\)
\(\underset{\underset{Methyl\ acetate}{(s)}}{CH_3COOCH_3}+NaOH\rightarrow\underset{\underset{sodium\ ethanoate}{(R)}}{CH_3COONa}+\underset{\underset{Method}{(A)}}{CH_3OH}\)