In three separate experiments a student produces the gases carbon dioxide, hydrogen and oxygen and needs to identify each one. (a) Complete Table 14.1 by gi...
Question 1 Report
In three separate experiments a student produces the gases carbon dioxide, hydrogen and oxygen and needs to identify each one.
(a) Complete Table 14.1 by giving a test and the positive result for each gas. [6]
| Gas | Test | Positive result |
|---|---|---|
| carbon dioxide | ||
| hydrogen | ||
| oxygen |
Answer Details
This tests the three standard gas tests. Each pairs an action with the observation that identifies the gas.
(a) The completed table is: [6]
| Gas | Test | Positive result |
|---|---|---|
| carbon dioxide | bubble the gas through limewater | the limewater turns milky (cloudy) |
| hydrogen | hold a lighted splint at the mouth of the tube | a squeaky pop is heard |
| oxygen | put a glowing splint into the gas | the splint relights (glows brighter) |
Each correct test scores one mark and each correct result scores one mark, giving six in total. The reasoning: carbon dioxide forms insoluble calcium carbonate with limewater (milkiness); hydrogen is flammable and burns explosively in a small amount of air (the pop); oxygen supports combustion, so it reignites a glowing splint.
Exam tip: keep the splint state straight, a lighted splint tests hydrogen, a glowing splint tests oxygen.
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