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9 (a) Water, acidified with sulfuric acid, is decomposed by electrolysis - Edexcel - GCSE Chemistry - Question 9 - 2019 - Paper 1
Question 9
9 (a) Water, acidified with sulfuric acid, is decomposed by electrolysis. (i) A sample of hydrogen is mixed with air and ignited. State what would happen. (ii) Th... show full transcript
Worked Solution & Example Answer:9 (a) Water, acidified with sulfuric acid, is decomposed by electrolysis - Edexcel - GCSE Chemistry - Question 9 - 2019 - Paper 1
Step 1
Step 2
Describe, using the data in Figure 9, what the results show about the volumes of hydrogen and of oxygen produced in this experiment.
Answer
The data in Figure 9 indicates that the volumes of hydrogen and oxygen produced are in a constant ratio. As the time progresses, the volume of hydrogen increases from 0 cm³ at 0 minutes to 16 cm³ at 8 minutes, while the volume of oxygen increases from 0 cm³ to 8 cm³ in the same time frame. The results demonstrate that for every 2 cm³ of hydrogen produced, 1 cm³ of oxygen is produced, aligning with the electrolysis reaction of water which follows the stoichiometric ratio of 2:1 for hydrogen to oxygen.
Step 3
Explain, in terms of solubility and movement of ions, this difference in behaviour.
Answer
Calcium nitrate is soluble in water, which allows it to dissociate into calcium ions (Ca²⁺) and nitrate ions (NO₃⁻). This dissociation enables the free movement of ions in solution, allowing electricity to flow and enabling it to act as an electrolyte.
In contrast, calcium carbonate is insoluble in water, meaning it does not dissociate into ions. Without free-moving ions, there is no conduction of electricity, and thus calcium carbonate does not behave as an electrolyte.