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3.3 Yield and atom economy of chemical reactions

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Question 30

A pilot plant makes sodium carbonate by heating sodium hydrogencarbonate.

2NaHCO3→Na2CO3+H2O+CO22\mathrm{NaHCO_3} \rightarrow \mathrm{Na_2CO_3} + \mathrm{H_2O} + \mathrm{CO_2}2NaHCO3​→Na2​CO3​+H2​O+CO2​

The desired product is sodium carbonate.

Relative formula masses (MrM_rMr​):

NaHCO3=84\mathrm{NaHCO_3} = 84NaHCO3​=84

Na2CO3=106\mathrm{Na_2CO_3} = 106Na2​CO3​=106

The percentage yield of sodium carbonate in one batch is 90%.

a.

Calculate the percentage atom economy for making sodium carbonate.

Give your answer to 3 significant figures.

[2]
b.

Explain why the percentage yield and the percentage atom economy for this batch have different values. Explain whether improving the method used to separate the sodium carbonate would change the atom economy.

[3]
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

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

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