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
Which observation shows that a gas has been produced?
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Answer
The correct observation to show that gas has been produced when sodium is added to water is:
B: effervescence is seen.
This indicates the formation of hydrogen gas, which creates bubbles that signify gas release.
Step 2
Which gas bleaches damp litmus paper?
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Answer
The gas that bleaches damp litmus paper is:
A: carbon dioxide.
This gas can react with the moisture in the paper to cause a bleaching effect.
Step 3
Calculate the mass of carbon dioxide that has been released.
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Answer
To calculate the mass of carbon dioxide (extCO2) released, we start by determining the initial mass of calcium carbonate.
Initial mass of CaCO₃: 5.000 g
Mass of solid remaining: 2.800 g
Mass of carbon dioxide released:
extMassofextCO2=extInitialmass−extRemainingmass=5.000extg−2.800extg=2.200extg
Thus, the mass of carbon dioxide released is 2.20 g (to three significant figures).
Step 4
Explain, using Figure 15, why helium is inert.
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Answer
Helium is considered inert because it has a complete outer shell of electrons.
This configuration means that helium does not easily engage in chemical reactions, as it doesn't need to gain or lose electrons to achieve stability.
Step 5
State one property of helium, apart from being inert, that makes it suitable for filling balloons.
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Answer
One property of helium that makes it suitable for filling balloons is its low density.
Helium is lighter than air, allowing balloons filled with it to float.
Step 6
Explain how the relative amount of each of the gases in Figure 16 has increased or decreased over time.
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Answer
The relative amounts of gases in the atmosphere have changed due to both natural processes and human activities:
Water Vapour: The amount of water vapor can increase due to evaporation from bodies of water.
Carbon Dioxide: This gas has decreased over time as plants absorb CO₂ for photosynthesis, although human activities such as burning fossil fuels can also increase its concentration in the atmosphere.
Oxygen: Initially very low, the amount of oxygen has significantly increased due to the process of photosynthesis carried out by plants, contributing to its present level of about 21% in the atmosphere.
