This question is about gases - Edexcel - GCSE Chemistry - Question 3 - 2022 - Paper 1
Question 3
This question is about gases.
(a) When sodium is added to water, hydrogen gas is produced.
Which observation shows that a gas has been produced?
A a white precip... show full transcript
Worked Solution & Example Answer:This question is about gases - Edexcel - GCSE Chemistry - Question 3 - 2022 - Paper 1
Step 1
Which observation shows that a gas has been produced?
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Answer
The correct answer is B: effervescence is seen. This indicates that gas bubbles are coming off the surface, thus confirming the production of hydrogen gas when sodium reacts with water.
Step 2
Which gas bleaches damp litmus paper?
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Answer
The correct answer is B: chlorine. Chlorine gas has the ability to bleach damp litmus paper, resulting in a color change.
Step 3
Calculate the mass of carbon dioxide that has been released.
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Answer
To find the mass of carbon dioxide released, we first calculate the mass lost during the decomposition of calcium carbonate:
Mass of calcium carbonate before heating: 5.000g
Mass of solid remaining after heating: 2.800g
Using the formula:
Mass of CO₂ = Initial mass - Remaining mass
Mass of CO₂ = 5.000g - 2.800g = 2.200g
Thus, the mass of carbon dioxide released is 2.200g, which is presented to three significant figures.
