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The speed of chemical reaction between gases increases with increase in pressure due to an increase in
1. The number of molecules
2. Volume
3. Concentration
4. Distance between molecules

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Correct Answer - Option 1 : The number of molecules

The correct answer is the number of molecules

  • The speed of chemical reactions between gases increases with an increase in pressure is due to an increase in the number of molecules that have the minimum activation energy required.
  • Explanation:
    • In the case of gases, increasing the pressure is equivalent to increasing the concentration as the number of collisions that occur among the gas molecules increases with an increase in pressure.
    • This, in turn, brings about a change in the reaction rate caused by increased kinetic energy and a greater number of collisions in unit time.
  • Logic:
    • Increasing the pressure for a reaction involving gases will increase the rate of reaction. As you increase the pressure of a gas, you decrease its volume (PV=nRT, P and V are inversely related), while the number of particles (n) remains unchanged.
    • Therefore, increasing pressure increases the concentration of the gas (n/V), and ensures that the gas molecules collide more frequently.
    • Keep in mind this logic only works for gases, which are highly compressible, changing the pressure for a reaction that involves only solids or liquids has no effect on the reaction rate.

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