A recycling plant receives aluminium trays contaminated with food. Fig. 1 shows a worker adding dilute sodium hydroxide solution to a small test sample of a...
Question 1 Report
A recycling plant receives aluminium trays contaminated with food. Fig. 1 shows a worker adding dilute sodium hydroxide solution to a small test sample of aluminium. Hydrogen gas is collected in a gas syringe. The plant only carries out this test in a ventilated area because hydrogen is flammable. The solution is an alkali and the aluminium is a metal.
(a) Give the gas formed when aluminium reacts with sodium hydroxide solution. [1]
(b) Describe how the gas syringe provides evidence that a reaction is occurring. [1]
(c) Give two precautions needed when testing the gas with a lit splint. [2]
The table below shows the pH of rainwater collected at three locations during one week. Fig. 1 shows a collector funnel leading to a clean bottle. Location S is close to a busy road, where fuels containing carbon compounds are burned. The environmental group is investigating whether acidic rain could damage limestone statues.
| location | mean pH of rainwater |
|---|---|
| Rural R | 5.6 |
| Roadside S | 4.4 |
| Coastal T | 5.3 |
(a) Use Table 1 to give the location with the most acidic rainwater. [1]
(b) Describe how the pH scale shows that location S is more acidic than location R. [1]
(c) Give two steps that make this comparison of rainwater samples fair. [2]
Answer Details
Aluminium and sodium hydroxide
(a) The gas formed is hydrogen. [1]
(b) The gas syringe provides evidence of reaction because its plunger moves as the volume of gas increases. [1]
(c) Test only a small sample of the gas and keep your face away from the splint and apparatus. Other valid precautions include wearing eye protection and keeping other flames away, because hydrogen is flammable. Any two are required. [2]
Rainwater investigation
(a) Roadside S has the most acidic rainwater because it has the lowest pH, 4.4. [1]
(b) Location S is more acidic than location R because S has a lower pH value: 4.4 compared with 5.6. [1]
(c) Collect the samples for the same length of time and use identical clean bottles or funnels. Other accepted controls include testing at the same temperature and using the same calibrated pH meter. Any two are required. [2]
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