Limestone is used to make many different materials - AQA - GCSE Chemistry - Question 2 - 2015 - Paper 1
Question 2
Limestone is used to make many different materials.
2 (a) Heating limestone produces calcium oxide and carbon dioxide.
Complete the sentences.
2 (a) (i) The main ... show full transcript
Worked Solution & Example Answer:Limestone is used to make many different materials - AQA - GCSE Chemistry - Question 2 - 2015 - Paper 1
Step 1
2 (a) (i) The main compound in limestone is calcium (calcium carbonate)
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Answer
The main compound in limestone is calcium carbonate (CaCO₃).
Step 2
2 (a) (ii) The reaction to produce calcium oxide from limestone is thermal (thermal decomposition)
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Answer
The reaction to produce calcium oxide from limestone is thermal decomposition, which involves heating limestone to drive off carbon dioxide.
Step 3
2 (a) (iii) Calcium hydroxide is produced when calcium oxide reacts with (water)
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Calcium hydroxide is produced when calcium oxide reacts with water, forming slaked lime (Ca(OH)₂).
Step 4
2 (a) (iv) Calcium hydroxide is used to neutralise acids because it is an (alkali)
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Calcium hydroxide is used to neutralise acids because it is an alkali, which can react with acids to form salt and water.
Step 5
2 (b) (i) One of the points is anomalous. Complete the graph in Figure 3 by drawing two straight lines of best fit.
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Answer
Draw a straight line through the first, second, and fourth points. Then draw a second straight line through the last four points, ensuring the lines are appropriately positioned based on the data.
Step 6
2 (b) (ii) Describe one way the students could improve the method so that their results are more accurate for each graph point.
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Answer
The students could repeat the experiment for each mass of aggregate to reduce random errors. Additionally, they could take multiple readings for each mass and calculate a mean value.
Step 7
2 (b) (iii) What force is needed to break a concrete beam containing no aggregate? Show your working on the graph.
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Answer
On the graph, extrapolate the line back to the y-axis to find the force for a mass of aggregate equal to zero. This value appears to be approximately 40 newtons.
Step 8
2 (b) (iv) The force needed to break a concrete beam increases as the mass of aggregate increases.
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Answer
The student's conclusion is partially correct. While it is true that the force generally increases with mass, there is a point where additional mass does not increase the force needed to break the beam. For example, at around 400g of aggregate, the force required peaks and starts to decrease, indicating that other factors affect the beam's strength.
