MCQ Detailed View

The Law of Mass Action is one of the most important principles in physical chemistry and chemical kinetics. It was proposed by the Norwegian scientists Cato Maximilian Guldberg and Peter Waage in 1864. This law provides a mathematical relationship between the rate of a chemical reaction and the concentrations of the reactants involved.

According to the law:
“The rate of a chemical reaction is directly proportional to the product of the active masses (concentrations) of the reacting substances, each raised to a power equal to its stoichiometric coefficient in the balanced equation.”

For example, consider a reaction:

$$aA+bB\to Products$$

According to the law of mass action:

Rate∝[A]a[B]b\text{Rate} \propto [A]^a [B]^bRate∝[A]a[B]b

Here:

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  [A] and [B] represent the molar concentrations of the reactants.

  
  


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  a and b are their stoichiometric coefficients.

  
  

This principle not only explains how reaction rates depend on concentration but also serves as the foundation for the concept of chemical equilibrium. At equilibrium, the forward and backward reaction rates become equal, leading to the equilibrium constant (K) expression:

K=[Products][Reactants]K = \frac{[Products]}{[Reactants]}K=[Reactants][Products]

The significance of Guldberg and Waage’s contribution cannot be overstated:

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  It laid the groundwork for modern chemical kinetics.

  
  


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  It helped explain Le Chatelier’s principle and shifts in equilibrium.

  
  


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  It is essential in industrial chemistry, for example in the Haber process (ammonia synthesis) and the Contact process (sulfuric acid production).

  
  

The incorrect options represent years in which other scientific discoveries were made, but 1864 is the correct historical year when the law of mass action was first proposed.

Thus, the Law of Mass Action was proposed by Guldberg and Waage in 1864, marking a milestone in the development of physical chemistry.