A laboratory supplier is developing a gas generator for filling collection vessels with gas Z. Each batch must finish quickly without reducing the amount of gas collected, and any powder added should be suitable for recovery and reuse.
In the generator, aqueous X forms Y and Z at room temperature.
2X(aq)→2Y(aq)+3Z(g)\mathrm{2X(aq) \rightarrow 2Y(aq) + 3Z(g)}2X(aq)→2Y(aq)+3Z(g)
Gas Z does not dissolve in water. Two insoluble powders, P and Q, may act as catalysts. They can be separated from the reaction mixture by filtration.
A student obtains these preliminary results using the same volume and concentration of X in each experiment.
| Powder added | Volume of Z after 40 s in cm3\mathrm{cm^3}cm3 | Final volume of Z in cm3\mathrm{cm^3}cm3 | Mass of powder added in g | Mass of dry powder recovered in g |
|---|---|---|---|---|
| none | 18 | 90 | — | — |
| P | 54 | 90 | 0.500 | 0.486 |
| Q | 63 | 72 | 0.500 | 0.310 |
Using the preliminary results, devise further work that would allow the student to decide which powder, if either, is a suitable catalyst for the gas generator. Explain how the results and the supplier's requirements should be used.
In another experiment, 40.0 cm3\mathrm{cm^3}cm3 of the solution of X reacts completely. The gas syringe contains air and reads 6.0 cm3\mathrm{cm^3}cm3 before the reaction. It reads 90.0 cm3\mathrm{cm^3}cm3 when the reaction is complete.
Calculate the concentration of X in mol dm−3\mathrm{mol\,dm^{-3}}moldm−3.
One mole of any gas occupies 24 000 cm3\mathrm{cm^3}cm3 at room temperature and pressure.
122 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.