4. (a) Water can be decomposed by electrolysis - Edexcel - GCSE Chemistry - Question 4 - 2011 - Paper 1
Question 4
4. (a) Water can be decomposed by electrolysis. Hydrogen and oxygen are formed. This apparatus can be used to carry out the electrolysis.
(i) Write the balanced equ... show full transcript
Worked Solution & Example Answer:4. (a) Water can be decomposed by electrolysis - Edexcel - GCSE Chemistry - Question 4 - 2011 - Paper 1
Step 1
Write the balanced equation for water decomposing to form hydrogen and oxygen.
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Answer
The balanced equation for the electrolysis of water is:
2H2O→2H2+O2
This reaction shows that two molecules of water decompose to form two molecules of hydrogen gas and one molecule of oxygen gas.
Step 2
Describe the test to show that a gas is hydrogen.
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Answer
To test for hydrogen gas, a lighted splint should be introduced into the gas. If hydrogen is present, it will ignite with a characteristic pop sound, indicating its presence.
Step 3
Describe the test to show that a gas is oxygen.
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Answer
To test for oxygen gas, a glowing splint should be used. When the glowing splint is placed into the gas, it will relight, confirming the presence of oxygen.
Step 4
Complete the sentence by putting a cross (✗) in the box next to your answer.
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Answer
The toxic gas produced is:
B) chlorine
Step 5
Give a safety precaution that should be taken when collecting this toxic gas.
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Answer
When collecting chlorine gas, it is important to perform the process in a well-ventilated area or under a fume hood to avoid inhaling the toxic gas.
Step 6
Give the name of the acid that must be used.
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Answer
The acid that must be used to prepare sodium chloride solution is hydrochloric acid.
