The enthalpies of combustion of acetaldehyde and paraldehyde (a polymer of acetaldehyde) are -1167 and -3477 kJ/mol, respectively. The enthalpy of polymerization per mole of paraldehyde is -24 kJ. The

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The enthalpies of combustion of acetaldehyde and paraldehyde (a polymer of acetaldehyde) are -1167 and -3477 kJ/mol, respectively. The enthalpy of polymerization per mole of paraldehyde is -24 kJ. The molecular formula of paraldehyde is

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Cycle: 1 mol paraldehyde → n mol CH 3 CHO (depolymerization, ΔH = +24 kJ) → combustion of n mol CH 3 CHO (-1167n kJ). Equating with direct combustion: -3477 = 24 - 1167n, so n = 3501/1167 = 3. Formula (C 2 H 4 O) 3 = C 6 H 12 O 3 . This is option (c).

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