Question

Write the expression for the equilibrium constant Kc for the following reaction: 4 NO(g) + 6H2O (g) ↔ 4 NH3 (g) + 5 O2 (g)

Answer 1

Law of Mass Action :

• It was put forward by Guldberg and Waag.
• It states that the rate at which a substance reacts is directly proportional to its active mass and hence the rate at which substances react together is directly proportional to the product of their active masses.
• Active mass means molar concentration.

Law of Chemical Equilibrium :

For the reaction,

$\star\bf\:aA+bB\:\rightleftharpoons\:xX+yY$

Equilibrium constant is given by

$\dag\:\underline{\boxed{\bf{\orange{K_c=\dfrac{[X]^x[Y]^y}{[A]^a[B]^b}}}}}$

Where Kc is called equilibrium constant at constant temperature.

For the given chemical reaction,

$\dag\:\underline{\boxed{\bf{\gray{K_c=\dfrac{[NH_3]^4[O_2]^5}{[NO]^4[H_2O]^6}}}}}$

Additional Information :

• A reaction is said to be in equilibrium when the rate of forward reaction becomes equal to the rate of backward reaction.
• At equilibrium the concentration of each of the reactants and products becomes constant.
• A chemical equilibrium can be established only if none of the products is allowed to escape out.