2 (a) When chromium reacts with oxygen, chromium oxide is formed - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2021 - Paper 1
Question 2
2 (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:2 (a) When chromium reacts with oxygen, chromium oxide is formed - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2021 - Paper 1
Step 1
Write the word equation for this reaction.
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Answer
Chromium + Oxygen → Chromium Oxide
Step 2
What type of reaction occurs when chromium reacts with oxygen?
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Answer
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 Cr₂O₃:
Chromium (Cr) has an atomic mass of 52 g/mol.
Oxygen (O) has an atomic mass of 16 g/mol.
The relative formula mass is given by:
extRelativeFormulaMass=2(extmassofCr)+3(extmassofO)
Substituting the values, we get:
=2(52)+3(16)=104+48=152
Thus, the relative formula mass of Cr₂O₃ is 152 g/mol.
Step 4
Place the metals in order of reactivity from most to least reactive.
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Answer
Most reactive: Magnesium
Least reactive: Silver
Step 5
What is the safest way to ignite the gas?
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Answer
C put a lighted splint at the open end of the test tube.
Step 6
State the observation made in this test that shows that the gas is hydrogen.
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Answer
A popping sound is heard when the gas ignites.
Step 7
State why iron can be extracted by heating iron oxide with carbon.
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Answer
Iron can be extracted because carbon reduces iron oxide to iron by displacing it, and this process is exothermic.
Step 8
State why electrolysis is not used to extract iron.
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Electrolysis is not used to extract iron because it is an expensive process and the required temperature would need to be significantly high for effective separation.
