When 20 g of ${\mathrm{CaCO}}_3$ were put in 10-liter flask and heated to 800°C,35% of ${\mathrm{CaCO}}_3$ remained unreacted at equilibrium. ${\mathrm{K}}_{\mathrm{P}}$ for decomposition of ${\mathrm{CaCO}}_3 \mathrm{is}$