Question

What is the difference between rate law expression and the rate obtained from law of mass action?

• A. Rate law expression is experimentally obtained, while law of mass action is theoretically obtained
• B. Rate law expression is theoretically obtained, while law of mass action is experimentally obtained
• C. Law of mass action depends on the stoichiometric co-efficeient of the reactants, while rate law expression may or may not
• D. Rate law expression depends on the stoichiometric co-efficient of the reactants, while law of mass action doesn't

Answer 1

Answer: (A), (C)

The correct options are
A Rate law expression is experimentally obtained, while law of mass action is theoretically obtained
C Law of mass action depends on the stoichiometric co-efficeient of the reactants, while rate law expression may or may not

Law of mass action states that at the constant temperature, the rate of a chemical reaction is directly proportional to the product of the molar concentrations of reacting species with each concentration term raised to the power of stoichiometric coefficient of that species in the chemical equation.

Eg:$2A+3B⟶$Products

According to this law

$r\propto {\left[A\right]}^2{\left[B\right]}^3$

$r=k{\left[A\right]}^2{\left[B\right]}^3$

where k is the rate constant.

The rate law for a chemical reaction is obtained experimentally in order to explain the kinetics of a reaction.

Rate law may or may not depend on the stoichiometric coefficient of the reactants.