Question

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

Answer 1

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.