A student investigates the reaction between zinc and dilute sulfuric acid to produce hydrogen gas.
They measure the time taken to collect 50 cm350\text{ cm}^350 cm3 of hydrogen gas. Without any catalyst, this time is 150 seconds.
The student investigates four solid substances, W, X, Y, and Z, as potential catalysts for this reaction.
| Substance | Appearance of substance | Time to collect 50 cm350\text{ cm}^350 cm3 of hydrogen (s) | Other observations |
|---|---|---|---|
| W | white powder | 150 | colourless solution formed |
| X | black powder | 35 | black powder remains |
| Y | orange powder | 35 | blue solution formed |
| Z | grey powder | 150 | grey powder remains |
Which substance, W, X, Y or Z, is a catalyst for the reaction?