ThermochemistryHard

Question

Diborane is a potential rocket fuel which undergoes combustion according to the following reaction.

B2H6(g) + 3O2(g) → B2O3(s) + 3H2O(g)

From the following data, calculate the enthalpy change for the combustion of diborane.

2B(s) + 3/2 O2(g) → B2O3(s): ΔH = −1273 kJ/mol

H2(g) + ½ O2(g) → H2O(l): ΔH = −286 kJ/mol

H2O(l) → H2O(g): ΔH = 44 kJ/mol

2B(s) + 3H2(g) → B2H6(g): ΔH = 36 kJ/mol

Options

A.−2167 kJ/mol
B.−1478 kJ/mol
C.−2035 kJ/mol
D.−1999 kJ/mol

Solution

From (i) + 3(ii) + 3(iii) – (iv); ΔH = –2035 KJ

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