Collision Theory
Kinetics Worksheet
Collision Theory Questions
1. You are conducting a reaction between magnesium and sulfuric acid.
a) Write the equation for the reaction.
Mg + H2SO4 → MgSO4 + H2
b) Collisions between Magnesium atoms and hydrogen ions are required for a reaction to occur, but not all collisions result in a reaction. Explain why this is the case.
- Colliding particles must have at least as much energy as the activation energy. Some collisions happen with less energy than that.
- Additionally, many reactions require the particles to have the correct orientation.
c) You change the acid from sulfuric acid to hydrochloric acid but keep everything else constant. Describe and explain the effect this has on the rate of reaction. You may assume that both acids are strong acids.
- Sulfuric acid is diprotic, whereas hydrochloric acid is monoprotic. The concentration of the H+ ions has been halved.
- This causes the frequency of collisions to halve as well.
- The proportion of successful collisions is unchanged, so the frequency of successful collisions is halved.
- This results in the rate of reaction being halved.
- (Note: The relationship between concentration and rate is not always directly proportional, though it is in this case.)
d) You increase the temperature of the mixture. Describe and explain the effect this has on the rate of reaction.
- The particles have more energy and they move faster.
- The increase in the speed results in more frequent collisions.
- The increase in the energy results in a higher proportion of the collisions having enough energy.
- The factors combine together to make the frequency of successful collisions higher and therefore increase the rate of reaction.
2. In a separate reaction, you are reacting CO and NO to make CO2 and N2.
a) Describe and explain what will happen to the rate if you decrease the volume of the reaction container but keep everything else constant.
- The space between the particles has decreased.
- This increases the frequency of collisions.
- As the proportion of collisions that are successful is unchanged, this increases the frequency of successful collisions.
b) Describe and explain what will happen to the rate if you add a Rhodium catalyst.
- The catalyst will provide an alternative reaction pathway with a lower activation energy.
- This doesn’t increase the frequency of collisions but does increase the proportion of collisions that occur with enough energy.
- This results in a higher frequency of successful collisions, increasing the rate of reaction.