Question

If the value of an equilibrium constant for a particular reaction is $1.6\text{ x 1}{{\text{0}}^{12}}$, then at equilibrium the system will contain:
(a)- Mostly products
(b)- Similar amounts of reactants and products
(c)- All reactants
(d)- Mostly reactants

Answer 1

The amount of reaction completion can be determined by the value of the equilibrium constant. If the value is small then the reaction is very slow, if the value is moderate, then the reaction rate is also moderate, and if the value is large then the reaction is very fast.

Complete answer:
The equilibrium constant of a reaction can be used to predict the extent of the reaction and it gives the idea of the amount of reactants and products in a reaction.
If the value is small then the reaction is very slow, if the value is moderate, then the reaction rate is also moderate, and if the value is large then the reaction is very fast.
(i)- If the value of the equilibrium constant is > ${{10}^{3}}$, then the reaction will contain mostly products and the rate of reaction is very fast.
(ii)- If the value of the equilibrium constant is ${{10}^{-3}}\text{ to 1}{{\text{0}}^{3}}$, then the reaction will have a similar amount of reactant and product and the rate of reaction will be moderate.
(iii)- If the value of the equilibrium constant is < ${{10}^{-3}}$, the reaction will be mostly reactant and the rate of reaction will be slow.
So, in the given question the equilibrium constant is $1.6\text{ x 1}{{\text{0}}^{12}}$, which is very high, therefore, the reaction will mostly have products, and the reaction will be almost to completion.

Hence, the correct answer is an option (a)- Mostly products.

Note:
There is another property concentration quotient, Q, that can be used to predict the direction of the reaction. If Q = K, then the reaction is in equilibrium, if Q > K, the reactants are more than products, and if Q < K, the products are more than the reactant.