Question

Attempt either option (A) or (B):

(A) (i) State any two reasons for carbon forming a large number of compounds. Why does carbon form compounds mainly by covalent bonds? (ii) Identify the compound which contains aldehyde as its functional group: $C_3H_7OH$ , $C_3H_7Cl$ , $C_2H_5CHO$ , $CH_3COCH_3$ .

OR

(B) (i) An organic compound 'X' is a constituent of wine. 'X' on reacting with acidified $K_2Cr_2O_7$ forms another compound 'Y' with molecular formula $C_2H_4O_2$ . 'Y' produces brisk effervescence with sodium carbonate. (a) Identify 'X' and 'Y'. (b) Name the gas evolved when 'Y' reacts with sodium carbonate. (c) Write the chemical equations involved for the chemical reactions taking place.

Accepted Answer

C2H5CHO contains aldehyde group. X is ethanol (C2H5OH), Y is ethanoic acid (CH3COOH), gas evolved is CO2.. **Option (A):** (i) Reasons: Catenation and Tetravalency. Carbon cannot lose 4 electrons ($C^{4+}$ requires huge energy) nor gain 4 electrons ($C^{4-}$ is unstable due to electron repulsion), so it shares electrons forming covalent bonds. (ii) $C_2H_5CHO$ contains the aldehyde group ($-CHO$). **Option (B):** (a) 'X' is Ethanol ($C_2H_5OH$), 'Y' is Ethanoic acid ($CH_3COOH$). (b) Gas evolved is Carbon dioxide ($CO_2$). (c) Equations: 1) $C_2H_5OH \xrightarrow{	ext{Acidified } K_2Cr_2O_7 + 	ext{Heat}} CH_3COOH + H_2O$ 2) $2CH_3COOH + Na_2CO_3 ightarrow 2CH_3COONa + H_2O + CO_2\uparrow$

Covalent Bonding of Carbon and Functional Groups

Explanation

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