4 (a) When chromium reacts with oxygen, chromium oxide is formed - Edexcel - GCSE Chemistry - Question 4 - 2021 - Paper 1
Question 4
4 (a) When chromium reacts with oxygen, chromium oxide is formed.
(i) Write the word equation for this reaction.
(ii) What type of reaction occurs when chromium re... show full transcript
Worked Solution & Example Answer:4 (a) When chromium reacts with oxygen, chromium oxide is formed - Edexcel - GCSE Chemistry - Question 4 - 2021 - Paper 1
Step 1
Write the word equation for this reaction.
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Answer
The word equation for the reaction is:
chromium + oxygen → chromium oxide
Step 2
What type of reaction occurs when chromium reacts with oxygen?
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Answer
The type of reaction that occurs is:
D oxidation
Step 3
Calculate the relative formula mass of chromium oxide, Cr₂O₃.
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Answer
To calculate the relative formula mass of chromium oxide (Cr₂O₃):
Chromium (Cr): 2 atoms × 52 = 104
Oxygen (O): 3 atoms × 16 = 48
Total relative formula mass = 104 + 48 = 152
Relative formula mass = 152
Step 4
Place the metals in order of reactivity from most to least reactive.
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The order of metals from most reactive to least reactive is:
Magnesium (steady bubbling)
Iron (very slow bubbling)
Silver (no change seen)
Step 5
What is the safest way to ignite the gas?
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C put a lighted splint at the open end of the test tube is the safest way to ignite the gas.
Step 6
State the observation made in this test that shows that the gas is hydrogen.
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The observation that shows the gas is hydrogen is:
