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30/09/2021 2:39 pm
Topic starter
Boron can undergo the following reactions with
the given enthalpy changes:
2B(s) + 3/2O2(g) → B2O3(s); ΔH = -1260 kJ
2B(s) + 3H2(g) → B2H6(g); ΔH = 30 kJ
Assume no other reactions are occurring.
If in a container (operating at constant pressure) which is isolated from the surrounding, mixture of H2(gas) and O2(gas) are passed over excess of B(s), then calculate the molar ratio (O2 : H2) so that temperature of the container do not change :
(a) 15 : 3
(b) 42 : 1
(c) 1 : 42
(d) 1 : 84
1 Answer
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30/09/2021 3:00 pm
Correct answer: (d) 1 : 84
Explanation:
No. of moles of O2 required to supplied 30 kJ heat to second reaction
= \(\frac{30}{1260}\) x \(\frac{3}{2}\) = \(\frac{1}{28}\)
nO2 : nH2 = \(\frac{1}{28}\) : 3
or 1 : 84