Q.Give a balanced chemical equation for the equilibrium reaction for which the equilibrium constant is given by expression Kc = [NH3]^4 [O2]^5 / ([NO]^4 [H2O]^6).

For a general reversible reaction $xA+yB\rightleftharpoons lC+mD$, the equilibrium constant is the ratio, at a fixed temperature, of the product of the active masses of the products (each raised to its own stoichiometric coefficient) to the product of the active masses of the reactants (likewise raised to their coefficients):

When every species in the reaction is gaseous, the same equilibrium can equally be described using partial pressures instead of concentrations:

$K_C$ (or $K_P$) is a genuine constant at a given temperature -- it does not change if the starting concentrations are changed (doubling the initial concentrations of A and B in $A+B\rightleftharpoons C$ changes the equilibrium composition the system settles into, but not the numerical value of $K_C$ itself, since $K_C$ depends only on temperature). It changes only if the temperature changes (the relationship is made quantitative by the Van't Hoff equation). …