Question

A reaction is said to be in equilibrium when :

• A. the rate of transformation of reactants to products is equal to the rate of transformation of products to the reactants.
• B. $50\%$ of the reactants are converted to products.
• C. the reaction is near completion and all the reactants are converted to products.
• D. the volume of reactants is just equal to the volume of the products.

Answer 1

The correct option is A the rate of transformation of reactants to products is equal to the rate of transformation of products to the reactants.

A reaction is said to be in equilibrium when the rate of transformation of reactants to products is equal to the rate of transformation of products to the reactants i.e the rate of forward reaction is equal to the rate of backward reaction.
Equilibrium is the state of a system in which its energy distribution is such that all parts of the system have the same temperature, and no heat flows.
There are three types of equilibrium :

• Thermal : Total energy remains constant at constant temperature.
  
• Chemical : Composition of reactants and products does not change with time.
  
• Mechanical: No moment of matter with respect to its surroundings.