How does a catalyst work?
3 marks · NormalA reaction without a catalyst has an activation energy of 180 kJ/mol. When a catalyst is added, the activation energy decreases to 100 kJ/mol.
Calculate the difference in activation energy as a result of adding the catalyst.
Explain what this change means for the number of successful collisions.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
80 kJ/mol lower; more collisions now have enough energy to react. kJ/mol (±1)
Also accept: More collisions have energy ≥ 100 kJ/mol so more are successful
Common mistakes: Saying all collisions are successful; giving wrong unit
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Sets up calculation for difference: 180 - 100.
A1 · 1 mark · Correctly calculates the difference as 80 kJ/mol.
B1 · 1 mark · Explains that more collisions are successful because more particles have energy greater than or equal to the new activation energy.
Worked solution
The activation energy is lowered by 80 kJ/mol.
This means that more particles now have enough energy to overcome the activation energy barrier, so there are more successful collisions and the reaction goes faster.