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 r... 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 between chromium and oxygen 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 when chromium reacts with oxygen 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 Cr₂O₃:
Relative formula mass = (2 × atomic mass of Cr) + (3 × atomic mass of O)
Substituting the values:
Relative formula mass = (2 × 52) + (3 × 16) = 104 + 48 = 152
Step 4
Place the metals in order of reactivity from most to least reactive.
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From the observations provided, the order of reactivity from most to least reactive is:
Most reactive: Magnesium > Iron > Silver: Least reactive
Step 5
What is the safest way to ignite the gas?
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Answer
The safest way to ignite the hydrogen gas is:
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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The observation that indicates the gas is hydrogen is:
A 'pop' sound is heard when a lighted splint is placed in the test tube.
Step 7
State why iron can be extracted by heating iron oxide with carbon.
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Iron can be extracted by heating iron oxide with carbon because:
Carbon reduces iron oxide to form iron and carbon dioxide.
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 compared to other methods like reduction with carbon.
