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This question is about gases - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1
Question 9
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? (b) Some damp lit... show full transcript
Worked Solution & Example Answer:This question is about gases - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1
Step 1
When sodium is added to water, hydrogen gas is produced. Which observation shows that a gas has been produced?
Answer
The correct observation that indicates the production of gas is B: effervescence is seen. This is a common sign that gas bubbles are being produced during the reaction of sodium with water.
Step 2
Some damp litmus paper is placed in a gas. The litmus paper is bleached. Which gas bleaches damp litmus paper?
Answer
The gas that bleaches damp litmus paper is A: carbon dioxide. This reaction occurs because carbon dioxide can create carbonic acid when dissolved in water, leading to the bleaching effect on the litmus paper.
Step 3
When calcium carbonate is heated, it decomposes. Calculate the mass of carbon dioxide that has been released.
Answer
To find the mass of carbon dioxide released, subtract the mass of the remaining solid (2.800g) from the original mass of calcium carbonate (5.000g):
Thus, the mass of carbon dioxide released is 2.20g (to three significant figures).
Step 4
Explain, using Figure 15, why helium is inert.
Answer
Helium is considered inert due to its complete outer shell of electrons, as shown in Figure 15. This full outer shell means that helium does not readily gain or lose electrons, making it chemically stable and unreactive with other elements.
Step 5
State one property of helium, apart from being inert, that makes it suitable for filling balloons.
Answer
One property of helium that makes it suitable for filling balloons is that it is lighter than air. This allows helium-filled balloons to float, making them ideal for decoration and celebration.
Step 6
Explain how the relative amount of each of the gases in Figure 16 has increased or decreased over time.
Answer
Over time, the relative amounts of gases as shown in Figure 16 have changed due to various natural processes and human activities.
- Water Vapour: The amount has decreased generally due to climate changes and the cooling of the earth's surface.
- Carbon Dioxide: The levels have increased significantly due to human activities such as burning fossil fuels and deforestation, contributing to climate change.
- Oxygen: The oxygen levels have increased as a result of photosynthesis from plants and algae, which produce oxygen as a byproduct. This has led to a stable percentage of oxygen in our current atmosphere.