What are catalysts?
4 marks · NormalThe table shows the volume of oxygen gas collected over 60 seconds when hydrogen peroxide is decomposed using three different solids as potential catalysts. The experiment used the same conditions (temperature, concentration, volumes).
| Time (s) | MnO2 (cm³) | PbO2 (cm³) | CuO (cm³) |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 20 | 24 | 8 | 0 |
| 40 | 36 | 13 | 0 |
| 60 | 40 | 16 | 0 |
Compare the effectiveness of the three solids as catalysts for this reaction.
Using evidence from the data, explain your answer.
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
(a) MnO2 is the most effective catalyst, PbO2 is less effective, and CuO does not act as a catalyst for this reaction. · must show Ranking all three solids
(b) MnO2 produced the most oxygen (40 cm³ in 60s), PbO2 produced 16 cm³, and CuO produced none. · must show Supports answer with figures from the table
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies MnO2 as most effective, PbO2 as less effective, CuO as not effective.
B2 (a) · 1 mark · States that not all are effective/compares their effectiveness in order.
B3 (b) · 1 mark · Refers to actual volumes/figures from the data to justify answer.
B4 (b) · 1 mark · Uses data for all three solids to support statements.
Worked solution
(a) MnO2 is the most effective catalyst, PbO2 is also a catalyst but less effective, and CuO has no catalytic effect.
(b) This is shown by the oxygen produced: with MnO2, 40 cm³ is collected after 60 seconds; with PbO2, only 16 cm³ is produced; CuO produces 0 cm³ oxygen gas in 60 seconds.