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3.3 Yield and atom economy of chemical reactions

3.3 Yield and atom economy of chemical reactions

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Question 9

Calcium carbonate is an insoluble salt used in dietary supplements and manufacturing. It can be prepared by mixing solutions of calcium chloride and sodium carbonate:

CaCl2(aq)+Na2CO3(aq)→CaCO3(s)+2NaCl(aq) \text{CaCl}_2\text{(aq)} + \text{Na}_2\text{CO}_3\text{(aq)} \rightarrow \text{CaCO}_3\text{(s)} + 2\text{NaCl(aq)} CaCl2​(aq)+Na2​CO3​(aq)→CaCO3​(s)+2NaCl(aq)

A student carried out an experiment to investigate the law of conservation of mass:

  1. Pour calcium chloride solution into beaker A.
  2. Pour sodium carbonate solution into beaker B.
  3. Measure the masses of both beakers and their contents.
  4. Pour the contents of beaker B into beaker A.
  5. Measure the masses of both beakers and their contents again.

The student's measurements are recorded in the table below:

Mass before mixing (g)Mass after mixing (g)
Beaker A and contents94.27131.63
Beaker B and contents73.4836.12
a.

Explain how the results demonstrate the law of conservation of mass. You must use data from the table in your answer.

[3]
b.

Calculate the percentage atom economy for the production of calcium carbonate (CaCO3\text{CaCO}_3CaCO3​) in this reaction. Give your answer to 3 significant figures.

Relative formula masses (MrM_{\text{r}}Mr​): CaCl2=111\text{CaCl}_2 = 111CaCl2​=111, Na2CO3=106\text{Na}_2\text{CO}_3 = 106Na2​CO3​=106, CaCO3=100\text{CaCO}_3 = 100CaCO3​=100, NaCl=58.5\text{NaCl} = 58.5NaCl=58.5

[4]
Markscheme

3.3 Yield and atom economy of chemical reactions Questions

  1. GCSE
  2. /Chemistry
  3. /3.3 Yield and atom economy of chemical reactions

31 exam-style questions on AQA GCSE Chemistry 3.3 Yield and atom economy of chemical reactions, covering 3.3.1 Percentage yield and 3.3.2 Atom economy. Each one has a worked solution and a mark scheme showing where the marks go.

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