MCQ Detailed View

Graham’s Law of Effusion is a fundamental principle in physical chemistry that explains the relationship between the rate of gas effusion and its molecular mass or density. Effusion is the process by which gas particles pass through a tiny hole without collisions with other particles. According to Graham’s Law, the rate of effusion of a gas is inversely proportional to the square root of its density or molar mass.

Mathematically, it is expressed as:
Rate ∝ 1 / √Density or Rate ∝ 1 / √Molar Mass

This means that lighter gases effuse faster than heavier gases. For example, hydrogen (H₂) effuses much more quickly than oxygen (O₂) because hydrogen has a much smaller molar mass.

Looking at the options:

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  Graham’s Law is correct, as it directly relates effusion rate with density.

  
  


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  Gay-Lussac’s Law deals with the relationship between pressure and temperature of a gas, not effusion.

  
  


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  Boyle’s Law describes the inverse relationship between pressure and volume of a gas at constant temperature.

  
  


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  None of these is incorrect because Graham’s Law is the valid answer.

  
  

Graham’s Law is important in separating gases and in understanding diffusion and effusion processes. It also has practical applications in areas like isotope separation and gas analysis.

Thus, the principle that the rate of effusion is inversely proportional to the square root of density is explained by Graham’s Law.