Question: 88. Higher yield of NO in \mathrm{N}_{2}(\mathrm{~g})+\mathrm{O}_{2} \rightleftharpoons 2 \mathrm{NO}(\mathrm{g}) can be obtained at \left[\Delta \mathrm{H}\right. of the reaction \left.=+180.7 \mathrm{~kJ} \mathrm{~mol}^{-1}\right]
A. higher temperature
B. lower temperature
C. higher concentration of \mathrm{N}_{2}
D. higher concentration of \mathrm{O}_{2}
Choose the correct answer from the options given below:
(1) A, D only
(2) B, C only
(3) B, C, D only
(4) A, C, D only
Answer: Option (4)
Explanation:
The given reaction has a positive enthalpy change
\Delta H = +180.7 \ \mathrm{kJ \ mol^{-1}},
which means the reaction is endothermic.
According to Le Chatelier’s principle,
increasing the temperature favours the forward reaction in an endothermic process.
Therefore, higher temperature increases the yield of NO,
so statement A is correct.
Lower temperature would favour the backward reaction, decreasing NO formation, so statement B is incorrect.
Increasing the concentration of reactants shifts the equilibrium towards the product side.
Thus, higher concentration of \mathrm{N}_{2} increases NO formation,
making statement C correct.
Similarly, higher concentration of \mathrm{O}_{2}
also shifts the equilibrium to the right, increasing NO yield.
Hence, statement D is correct.
Therefore, the correct set of conditions for higher yield of NO is A, C and D.