Question

For which one of the following reactions, a combination of high pressure and high temperature is helpful in obtaining a high equilibrium yield?

• A. $2N{F}_3\left(g\right)\to N_2\left(g\right)+3F_2\left(g\right)-54.40k.cals$
• B. $N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)+22.08k.cals$
• C. $C{l}_2\left(g\right)+2O_2\left(g\right)\to 2Cl{O}_2\left(g\right)-49.4k.cals$
• D. $2C{l}_2{O}_7\left(g\right)\to 2C{l}_2\left(g\right)+7O_2\left(g\right)-126.8k.cals$

Answer 1

The correct option is C $C{l}_2\left(g\right)+2O_2\left(g\right)\to 2Cl{O}_2\left(g\right)-49.4k.cals$

When the forward reaction proceeds with a decrease in the number of moles, the increased pressure will shift the equilibrium towards right, which will decrease the number of moles and nullify the effect of increased pressure. This will increase the yield of the forward reaction.
When the temperature of an endothermic reaction is increased, the reaction will proceed in the forward direction so as to absorb heat and nullify the effect of increasing temperature. This will increase the value of the equilibrium constant $K_c$ and increase the yield of the reaction.
This is true for the reaction in option C, i.e., $C{l}_2\left(g\right)+2O_2\left(g\right)\to 2Cl{O}_2\left(g\right)-49.4k.cals$.