Question

For the reaction, $2 NO _{2}(g) \rightleftharpoons 2 NO (g)+ O _{2}(g)$ $\left(K_{c}=1.8 \times 10^{-6}\right.$ at $184^{\circ} C$ and R $=0.00831\, kJ / mol K$ ) When $K_{p}$ and $K_{c}$ are compared at $184^{\circ} C$, it is found that

• A. whether $K_{p}$ is greater than less than or equal to $K_{c}$ depends uupon the total gas pressure
• B. $K_{p}=K_{c}$
• C. $K_{p}$ is less than $K_{c}$
• D. $K_{p}$ is greater than $K_{c}$

Answer 1

Answer: (D)

$2 NO _{2}(g)=2 NO (g)+ O _{2}(g)$
$K_{c}=1.8 \times 10^{-6}$ at $184^{\circ} C (=457 K )$
$R=0.00831\, kJ\, mol ^{-1} K ^{-1}$
$K_{p}=K_{c}(R T)^{\Delta n_{g}}$
where,
$\Delta n_{g}=$ (gaseous products -gaseous reactants)
$=3-2=1$
$\therefore K_{p}=1.8 \times 10^{-6} \times 0.00831 \times 457$
$=6.836 \times 10^{-6} >1.8 \times 10^{-6}$
Thus, $K_{p} > K_{c}$