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 $Mg(HCO_3)_{2(s)} \rightleftharpoons MgCO_{3(s)} + CO_{2(g)} + H_2O_{(g)}$,the equilibrium constant $K_p = 64 \ atm^2$. Calculate the total pressure at equilibrium.

For the reaction $PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$,which of the following relations is correct?

In the reaction $PCl_5 \rightleftharpoons PCl_3 + Cl_2$,the partial pressures of $PCl_3$,$Cl_2$,and $PCl_5$ are $0.3 \ atm$,$0.2 \ atm$,and $0.6 \ atm$ respectively. If the partial pressures of $PCl_3$ and $Cl_2$ are doubled,what will be the partial pressure of $PCl_5$ in $atm$?

$K_{p} = 0.04 \ atm$ at $899 \ K$ for the equilibrium shown below. What is the equilibrium pressure of $C_{2}H_{6}$ when it is placed in a flask at $4.0 \ atm$ pressure and allowed to come to equilibrium?
$C_{2}H_{6(g)} \longleftrightarrow C_{2}H_{4(g)} + H_{2(g)}$

For the given equilibrium reaction $H_{2(g)} + I_{2(g)} \rightleftharpoons 2 HI_{(g)}$,choose the correct equation to calculate $K_p$.