Question

The work done during combustion of 9 × 10^-2 kg of ethane, C₂H₆ (g) at 300 K is ______.
(Given R = 8.314 J deg^-1, atomic mass C = 12, H = 1)

Options

• 6.236 kJ

• - 6.236 kJ

• 18.71 kJ

• - 18.71 kJ

Answer 1

The work done during combustion of 9 × 10^-2 kg of ethane, C₂H₆ (g) at 300 K is 18.71 kJ.

Explanation:

Work done in a chemical reaction,

W = - Δn_gRT

Where, Δn_g = number of moles of gaseous products - number of moles of gaseous reactants.

Reaction involved in combustion of ethane is,

\[\ce{C2H6 (g) + 7/2 O2(g) -> 2CO2(g) + 3H2O(l)}\]

∴ Δn_g = 2 - 4.5 = - 2.5

W = (2.5 mol)(8.314 JK^-1 mol^-1) × 300 K

= 6235.5 J = 6.2355 KJ

1 mole of C₂H₆ = 30 g of C₂H₆ 

Work done during combustion of 30 g of

C₂H₆ = 6.2355 kJ

∴ Work done during combustion of 90 g of

C₂H₆ = `(6.2355 xx 90)/30` = 18.7065 kJ

= 18.71 kJ