Chemical Thermodynamics Question 248
Question: Boron can undergo the following reactions with the given enthalpy changes: $ 2B( s )+\frac{3}{2}O_2( g )\xrightarrow{{}}B_2O_3( s );\Delta H=-1260kJ $
$ 2B(s)+3H_2(g)\xrightarrow{{}}B_2H_6(g);\Delta H=+30kJ $ Assume no other reactions are occurring. If in a container (operating at constant pressure) which is isolated from the surrounding, mixture of $ H_2 $ (gas) and $ O_2 $ (gas) are passed over excess of B(s), then calculate the molar ratio $ (O_2:H) $ so that temperature of the container do not change :
Options:
A) 15 : 3
B) 42 : 1
C) 1 : 42
D) 1 : 84
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Answer:
Correct Answer: D
Solution:
- No. of moles of $ O_2 $ required to supply 30 kJ heat to second reaction $ =\frac{30}{1260}\times \frac{3}{2}=\frac{1}{28} $
${n_{O_2}}:{n_{H_2}}=\frac{1}{28}:,or,1:28$
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