Some Group 1 and Group 7 elements are very reactive - OCR Gateway - GCSE Chemistry: Combined Science - Question 14 - 2019 - Paper 10
Question 14
Some Group 1 and Group 7 elements are very reactive.
Look at the reaction cycle.
Identify element A.
Identify compound B.
(i) Write a balanced equation for the re... show full transcript
Worked Solution & Example Answer:Some Group 1 and Group 7 elements are very reactive - OCR Gateway - GCSE Chemistry: Combined Science - Question 14 - 2019 - Paper 10
Step 1
Identify element A.
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Answer
Element A is likely sodium (Na), as it is a Group 1 element that reacts vigorously with water.
Step 2
Identify compound B.
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Compound B is sodium bromide (NaBr) since it forms when element A (sodium) reacts with bromine (Br₂).
Step 3
(i) Write a balanced equation for the reaction of element A with Br₂(l).
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The balanced equation for the reaction of sodium (Na) with bromine (Br₂) is:
2extNa(s)+extBr2(l)→2extNaBr(s)
Step 4
Identify compound C.
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Compound C is likely hydrogen bromide (HBr), as it is produced when the product from the first reaction dissolves in water and reacts with hydrochloric acid (HCl).
Step 5
(ii) Give a reason for your answer to (c)(i).
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The reason is that hydrogen bromide (HBr) is a colorless gas that can result from such a reaction, consistent with the reaction cycle described.
Step 6
test for carbon dioxide
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The test for carbon dioxide (CO₂) involves bubbling the gas through limewater (calcium hydroxide solution). If CO₂ is present, the limewater turns milky due to the formation of calcium carbonate.
Step 7
result with gas D
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If gas D is carbon dioxide, the limewater will turn milky.
Step 8
test for hydrogen
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To test for hydrogen gas (H₂), bring a lit splint close to the gas. If hydrogen is present, a 'pop' sound will be heard.
Step 9
result with gas D
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If gas D is hydrogen, a 'pop' sound will be heard when a lit splint is introduced.
Step 10
test for oxygen
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The test for oxygen involves using a glowing splint. If the splint reignites in the presence of oxygen (O₂), this indicates that oxygen is present.
Step 11
result with gas D
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If gas D is oxygen, the glowing splint will reignite when introduced to the gas.
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