MCQ Detailed View

Charles’s Law is one of the fundamental gas laws in physical chemistry. It was discovered by the French scientist Jacques Charles in 1787, though his findings were not formally published until later when they were popularized by Joseph Louis Gay-Lussac.

The law states:

$$V\propto T\text{(at constant pressure)}$$

or, mathematically,

V1T1=V2T2\frac{V_1}{T_1} = \frac{V_2}{T_2}T1V1=T2V2

where:

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  V = volume of the gas

  
  


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  T = temperature in Kelvin

  
  

This means that if the pressure of a gas is kept constant, its volume increases linearly with an increase in absolute temperature (Kelvin). Conversely, if temperature decreases, the volume decreases proportionally.For example, if a balloon is heated, it expands because the gas molecules inside gain kinetic energy, collide more forcefully with the container walls, and occupy a larger volume.

Historical Significance

Jacques Charles conducted experiments with hydrogen gas in balloons and observed that gases expand uniformly with increasing temperature. His work was part of the early studies in thermodynamics and helped establish the relationship between temperature and gas behavior. Although Charles discovered the law in 1787, Gay-Lussac published the results in 1802, often leading to confusion about credit.

Importance in Modern Chemistry

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  Charles’s Law is crucial in understanding the behavior of gases in everyday applications, such as hot air balloons, weather balloons, and air conditioning systems.

  
  


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  It laid the groundwork for the development of the Ideal Gas Law (PV = nRT), which combines all fundamental gas laws.

  
  


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  It highlights the importance of using the Kelvin scale, since the law breaks down if Celsius is used (because volume cannot be negative, while Celsius can be).

  
  

Key Facts

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  Discovered: 1787

  
  


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  Scientist: Jacques Charles

  
  


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  Relationship: V ∝ T at constant P

  
  


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  Practical Example: Expansion of heated balloons

  
  

Thus, the correct answer is 1787, marking the discovery of one of the most important gas laws in physical chemistry.