mixed solutions conical flask 0 20 40 60 gas syringe stopwatch Fig. 1 The table below shows results from a factory trial using cobalt(II) chloride solution ...
Question 1 Report
The table below shows results from a factory trial using cobalt(II) chloride solution as a catalyst in the reaction between sodium hydrogen sulfite solution and hydrogen peroxide. Fig. 1 shows the gas syringe used to collect the gas. Each trial used the same volumes and concentrations of both solutions at 25 °C.
| mass of cobalt(II) chloride / g | time to collect 30.0 cm3 gas / s |
|---|---|
| 0.00 | 180 |
| 0.10 | 92 |
| 0.20 | 55 |
| 0.30 | 53 |
(a) Describe the effect of increasing the mass of cobalt(II) chloride from 0.00 g to 0.20 g. [2]
(b) Use the results for 0.20 g of cobalt(II) chloride to calculate the mean rate of gas collection in cm3/s. [3]
(c) Give two variables that must be controlled to make this comparison valid. [2]
(d) Describe what should be done to the cobalt(II) chloride after a reaction if the factory wishes to reuse it. [2]
Answer Details
(a) Increasing the mass of cobalt(II) chloride from 0.00 g to 0.20 g decreases the time from 180 s to 55 s. Therefore the reaction rate increases: the catalyst speeds up the reaction. [2]
(b) mean rate = volume ÷ time
= 30.0 cm3 ÷ 55 s
= 0.545... cm3 s-1
= 0.55 cm3 s-1. [3]
(c) Keep the temperature constant and keep the volume or concentration of hydrogen peroxide constant. The volume or concentration of sodium hydrogen sulfite, and total solution volume, are also valid control variables. Any two. [2]
(d) Filter to separate the solid catalyst from the solution, then wash and dry it before reuse. [2]
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