Question

If $K_c=7.5\times {10}^{-9}$ at 1000 K for the reaction $N_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2NO\left(g\right)$, what is $K_c$ at 1000 K for the reaction $2NO\left(g\right)\rightleftharpoons N_2\left(g\right)+O_2\left(g\right)$?

• A. $0.65\times {10}^8$
• B. $1.3\times {10}^8$
• C. $2.6\times {10}^8$
• D. None of these

Answer 1

The correct option is B $1.3\times {10}^8$

$N_2\left(g\right)+O_2\left(g\right)\rightleftharpoons 2NO\left(g\right)$ $K_c=7.5\times {10}^{-9}$

so for reverse reaction,

$2NO\left(g\right)\rightleftharpoons N_2\left(g\right)+O_2\left(g\right)$

$K_c^{\prime }=1/K_c$

$=1.3\times {10}^8$