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3 (a) Carbon dioxide is one of the gases in the Earth's atmosphere - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2019 - Paper 1
Question 3
3 (a) Carbon dioxide is one of the gases in the Earth's atmosphere. The percentage of carbon dioxide in the Earth's atmosphere has changed over time. (i) Which row ... show full transcript
Worked Solution & Example Answer:3 (a) Carbon dioxide is one of the gases in the Earth's atmosphere - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2019 - Paper 1
Step 1
Which row of the table shows the approximate percentage of carbon dioxide thought to be in the Earth's early atmosphere and how this percentage changed to form the Earth's atmosphere today?
Answer
The correct answer is option A, which states that the approximate percentage of carbon dioxide in the Earth's early atmosphere was 5%, and it has increased over time to form the Earth's atmosphere today. This reflects geological and biological processes that have historically contributed to atmospheric changes.
Step 2
Explain two factors that cause the percentage of carbon dioxide in today's atmosphere to vary.
Answer
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Human Activities: Industrial processes, fossil fuel combustion, and deforestation significantly increase carbon dioxide levels due to the release of greenhouse gases into the atmosphere.
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Natural Processes: Volcanic eruptions and the respiration of organisms also contribute to variations in carbon dioxide levels. Seasonal changes in vegetation can affect how much CO₂ is absorbed or released, fluctuating the overall concentration.
Step 3
Explain why carbon dioxide has a low boiling point.
Answer
Carbon dioxide has a low boiling point of -78.5 °C because it is a simple molecular compound. The intermolecular forces between CO₂ molecules are weak van der Waals forces (or London dispersion forces), which require relatively low amounts of energy to overcome. Consequently, CO₂ transitions to a gaseous state at this low temperature.
Step 4
Calculate the number of molecules in 0.11g of carbon dioxide.
Answer
To calculate the number of molecules in 0.11 g of carbon dioxide:
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Determine the number of moles of CO₂:
ext{moles} = rac{ ext{mass}}{ ext{molar mass}} = rac{0.11 ext{ g}}{44 ext{ g/mol}} = 0.0025 ext{ moles}
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Use Avogadro's constant to find the number of molecules:
= 1.51 imes 10^{21} ext{ molecules} $$
Therefore, rounding to two significant figures, the answer is approximately 1.5 × 10²¹ molecules.