Question

(1) $N_2+2O_2\leftrightarrow 2N{O}_2;K_e=2\times {10}^{-31}$
(2) $2N{O}^{+}\leftrightarrow N_2+O_2;K_e=2.2\times {10}^{-31}$
(3) $2N_2{O}_5\leftrightarrow 2N_2+5O_2;K_e=3.8\times {10}^{-32}$
(4) $2N_2+O_2\leftrightarrow 2N_{2}O;K_e=4\times {10}^{-32}$
From the above data, the most stable oxide is:

• A. $N{O}_2$
• B. $NO$
• C. $N_2{O}_5$
• D. $N_{2}O$

Answer 1

The correct option is C $N_2{O}_5$

Most stable oxide is that whose formation const, $K_f$ is largest

(1) $N_2+2O_2\leftrightarrow 2N{O}_2$ $K_e=2\times {10}^{-31}$

$K_f=\sqrt{K_e}$ {$\because$ one mole $N{O}_2$ must be formed}

$=\sqrt{0.2}\times {10}^{-15}$

$\approx 0.44\times {10}^{-15}$

(2) $2N{O}^{+}\leftrightarrow N_2+O_2$ $K_e=2.2\times {10}^{-31}$

$K_f=\frac{1}{\sqrt{K_e}}=\frac{{10}^{15}}{\sqrt{0.22}}$

$\approx 0.13\times {10}^{15}$

(3) $2N_2{O}_5\leftrightarrow 2N_2+5O_2$ $K_e=3.8\times {10}^{-32}$

$K_f=\frac{1}{\sqrt{K_e}}\approx 0.512\times {10}^{16}$

(4) $2N_2+O_2\leftrightarrow 2N_{2}O$ $K_e=4\times {10}^{-32}$

$K_f=\sqrt{K_e}=2\times {10}^{-16}$

$\therefore N_2{O}_5$ is most stable.