Higher yield of NO in the reaction:

N₂(g) + O₂(g) ⇌ 2NO(g)

[ΔH of the reaction = +180.7 kJ mol⁻¹]

A. Higher temperature
B. Lower temperature
C. Higher concentration of N₂
D. Higher concentration of O₂

Choose the correct answer from the options given below:

The correct option is A, C, D only.

To determine the conditions that favor a higher yield of $\mathrm{NO}$ in the given reversible reaction, we apply Le Chatelier's Principle. This principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.
The given chemical equilibrium is:
$N_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2\mathrm{NO}\left(g\right)$
The enthalpy change for this reaction is:
$\mathrm{\Delta H}=+180.7kJ{mol}^{-1}$

Let's analyze the effects of temperature and concentration step-by-step:

1. Effect of Temperature:
Since $\mathrm{\Delta H}$ is positive ($\mathrm{\Delta H}>0$), the forward reaction is endothermic (it absorbs heat).
According to Le Chatelier's principle, increasing the temperature (Higher temperature) supplies heat to the system. The system counteracts this by shifting the equilibrium in the direction that absorbs heat, which is the forward direction. Thus, a higher temperature increases the yield of $\mathrm{NO}$. Therefore, statement A is correct, and statement B (lower temperature) is incorrect.

2. Effect of Concentration:
According to Le Chatelier's principle, if we increase the concentration of any reactant, the system will shift the equilibrium in the direction that consumes that reactant (the forward direction).
- Increasing the concentration of $N_2$ (Higher concentration of N₂) shifts the equilibrium to the right to consume the added $N_2$, producing more $\mathrm{NO}$. Thus, statement C is correct.
- Similarly, increasing the concentration of $O_2$ (Higher concentration of O₂) shifts the equilibrium to the right to consume the added $O_2$, producing more $\mathrm{NO}$. Thus, statement D is correct.

Conclusion:
The conditions that favor a higher yield of $\mathrm{NO}$ are higher temperature (A), higher concentration of $N_2$ (C), and higher concentration of $O_2$ (D).