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(III) Oxide
Step 2
What type of reaction occurs when chromium reacts with oxygen?
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Answer
D oxidation.
This is an oxidation reaction where chromium is oxidized by reacting with oxygen.
Step 3
Calculate the relative formula mass of chromium oxide, Cr2O3.
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Answer
To calculate the relative formula mass of Cr2O3, we need to sum the atomic masses of its constituent elements:
Chromium (Cr): 2 atoms × 52 = 104
Oxygen (O): 3 atoms × 16 = 48
Thus, the total relative formula mass is:
104+48=152
Therefore, the relative formula mass of Cr2O3 is 152.
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.
This method is the safest as it avoids direct exposure to flames.
Step 6
State the observation made in this test that shows that the gas is hydrogen.
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Answer
The observation that confirms the gas is hydrogen is the presence of a 'pop' sound when the gas is ignited. This characteristic sound indicates the production of water vapor when hydrogen burns.
