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04/10/2021 4:09 pm
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Diborane is a potential rocket fuel which undergoes combustion according to the equation
B2H6(g) + 3O2(s) → B2O3(s) + 3H2O(g)
Calculate the enthalpy change for the combustion of diborane. Given
(i) 2B(s) + 3/2O2(g) → B2O3(s); ΔH = -1273 kJ per mol
(ii) H2(g) + 1/2O2(g) → H2O(l); ΔH = -286 kJ per mol
(iii) H2O(l) → H2O(g); ΔH = 44 kJ per mol
(iv) 2B(s) + 3H2(g) → B2H6(g); ΔH = 36 kJ per mol
(a) +2035 kJ per mol
(b) -2035 kJ per mol
(c) +2167 kJ per mol
(d) -2167 kJ per mol
1 Answer
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04/10/2021 4:12 pm
Correct answer: (b) -2035 kJ per mol
Explanation:
For the equation
B2H6(g) + 3O2(s) → B2O3(s) + 3H2O(g)
Eqs. (i) + 3(ii) + 3 (iii) - (iv)
ΔH = -1273 + 3(-286) + 3(44) - 36
= -1273 - 858 + 132 - 36
= -2035 kJ/mol