Which of the following relations is correct for $k_f$ and $k_b$ in an equilibrium process that contains equal moles of reactants and products?

For the reaction $N_2O_{4(g)} \rightleftharpoons 2NO_{2(g)}$,$K_p = 0.492 \ atm$ at $300 \ K$. $K_c$ for the reaction at same temperature is . . . . . . $\times 10^{-2}$. (Given: $R = 0.082 \ L \ atm \ mol^{-1} \ K^{-1}$)

In the equilibrium system $AB_{(s)} \rightleftharpoons A_{(g)} + B_{(g)}$,if the equilibrium concentration of $A$ is doubled,the equilibrium concentration of $B$ will be .....

For the reaction $A_{(g)} \rightleftharpoons B_{(g)}$ at $495 \ K$,$\Delta_{r}G^{\circ} = -9.478 \ kJ \ mol^{-1}$. If we start the reaction in a closed container at $495 \ K$ with $22 \ mmol$ of $A$,the amount of $B$ in the equilibrium mixture is $x \ mmol$. Find $x$ (Round off to the nearest integer). $[R = 8.314 \ J \ mol^{-1} \ K^{-1}; \ln 10 = 2.303]$

At $300 \ K$,$K_C$ for the reaction $A_2B_{2(g)} \rightleftharpoons A_{2(g)} + B_{2(g)}$ is $100 \ mol \ L^{-1}$. What is its $K_p$ (in $atm$) at the same temperature? $(R = 0.082 \ L \ atm \ K^{-1} \ mol^{-1})$

$A_{(s)} \rightleftharpoons M_{(s)} + \frac{1}{2} O_{2(g)}$
The equilibrium constant for the reaction is $K_{p} = 4$. At equilibrium,the partial pressure of $O_{2}$ is $.... \ atm.$ (Round off to the nearest integer).