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Limestone contains calcium carbonate (CaCO₃) - AQA - GCSE Chemistry - Question 5 - 2014 - Paper 1
Question 5
Limestone contains calcium carbonate (CaCO₃). (a) Name the type of reaction that takes place when calcium carbonate is heated strongly. Name the products formed. (... show full transcript
Worked Solution & Example Answer:Limestone contains calcium carbonate (CaCO₃) - AQA - GCSE Chemistry - Question 5 - 2014 - Paper 1
Step 1
Step 2
Calculate the mean mass lost, taking account of any anomalies.
Answer
To calculate the mean mass lost:
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List the mass lost for each experiment:
- Experiment 1: 1.8 g
- Experiment 2: 1.0 g
- Experiment 3: 1.9 g
- Experiment 4: 1.7 g
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Anomaly check: The mass lost in Experiment 2 (1.0 g) is significantly lower than the others, indicating it might be an anomaly.
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Calculate the mean mass lost excluding the anomaly:
Mean mass lost = rac{1.8 + 1.9 + 1.7}{3} = rac{5.4}{3} = 1.8 ext{ g}
Thus, the mean mass lost is 1.8 g.
Step 3
The student used the chemical equation to calculate the maximum mass lost by 5.0 g of calcium carbonate when heated.
Answer
The maximum mass lost can be calculated based on the chemical reaction:
ightarrow ext{CaO} (s) + ext{CO}_2 (g)$$ From the equation, we see that 1 mole of calcium carbonate results in the loss of 1 mole of carbon dioxide. The molar mass of calcium carbonate (CaCO₃) is approximately 100.09 g, while the molar mass of carbon dioxide (CO₂) is approximately 44.01 g. Thus, the maximum mass loss can be calculated as follows: Maximum mass lost = \( \frac{44.01}{100.09} \times 5.0 \approx 2.2 \text{ g} \) ### Reasons for mean mass lost being less than 2.2 g: 1. **Impurities in limestone**: The limestone may not be pure calcium carbonate; the presence of impurities results in less carbon dioxide being produced during heating. 2. **Inadequate heating duration**: The limestone may not have been heated for a sufficient amount of time, leading to incomplete decomposition of calcium carbonate.