If the equilibrium constant for the reaction $A + 3B \rightleftharpoons 2C$ is $K_1$,then the equilibrium constant $K_2$ for the reaction $2C \rightleftharpoons A + 3B$ should be:

The compounds $A$ and $B$ are mixed in equimolar proportion to form the products,$A + B \rightleftharpoons C + D$. At equilibrium,one-third of $A$ and $B$ are consumed. The equilibrium constant for the reaction is:

The equilibrium constant expression for the reaction $P_{4(s)} + 5O_{2(g)} \rightleftharpoons P_4O_{10(s)}$ is:

Steam reacts with iron at high temperature to give hydrogen gas and $Fe_3O_{4(s)}$. The correct expression for the equilibrium constant is

For a chemical reaction $A \rightleftharpoons B, K_1 = 2.0$ and $B \rightleftharpoons C, K_2 = 0.01$. The equilibrium constant for the reaction $2C \rightleftharpoons 2A$ is $:-$

(i) $H_3PO_{4\text{(aq)}} \rightleftharpoons H^+{_{\text{(aq)}}} + H_2PO_4^-{_{\text{(aq)}}}$
(ii) $H_2PO_4^-{_{\text{(aq)}}} \rightleftharpoons H^+{_{\text{(aq)}}} + HPO_4^{2-}{_{\text{(aq)}}}$
(iii) $HPO_4^{2-}{_{\text{(aq)}}} \rightleftharpoons H^+{_{\text{(aq)}}} + PO_4^{3-}{_{\text{(aq)}}}$
The equilibrium constants for the above reactions at a certain temperature are $K_1$,$K_2$,and $K_3$ respectively. The equilibrium constant for the reaction $H_3PO_{4\text{(aq)}} \rightleftharpoons 3H^{+}{_{\text{(aq)}}} + PO_4^{3-}{_{\text{(aq)}}}$
$K = K_1 \times K_2 \times K_3$ is