A factory is choosing a process for making calcium sulfate, CaSO4\mathrm{CaSO_4}CaSO4.
Process K: CaCO3+H2SO4→CaSO4+CO2+H2O\mathrm{CaCO_3 + H_2SO_4 \rightarrow CaSO_4 + CO_2 + H_2O}CaCO3+H2SO4→CaSO4+CO2+H2O
Process L: CaCl2+Na2SO4→CaSO4+2NaCl\mathrm{CaCl_2 + Na_2SO_4 \rightarrow CaSO_4 + 2NaCl}CaCl2+Na2SO4→CaSO4+2NaCl
Relative formula masses: CaSO4=136\mathrm{CaSO_4}=136CaSO4=136, CO2=44\mathrm{CO_2}=44CO2=44, H2O=18\mathrm{H_2O}=18H2O=18, NaCl=58.5\mathrm{NaCl}=58.5NaCl=58.5
The theoretical yield of calcium sulfate is 1250 kg per batch for either process.
| Feature | Process K | Process L |
|---|---|---|
| percentage yield | 72% | 92% |
| time for one batch | 3.0 hours | 4.0 hours |
| operating cost, excluding treatment or income from other products | £980 per batch | £760 per batch |
| use of other products | carbon dioxide and water are treated as waste | sodium chloride is sold |
The factory will install one reaction vessel, so batches cannot overlap. A contract requires at least 7000 kg of calcium sulfate to be supplied every 24 hours.
A manager claims that the atom economy of Process K is 20 percentage points greater than the atom economy of Process L.
Calculate the difference in atom economy between the two processes. State whether the claim is supported.
Calculate the actual mass of calcium sulfate expected from one batch of each process.
Evaluate the proposal to install Process L. Include calculations to show whether each process could meet the contract.
151 exam-style questions on Edexcel GCSE Chemistry 6.2 Quantitative analysis, covering 6.2.1 Concentration in mol dm⁻³ and titration calculations, 6.2.2 Percentage yield and why actual yield falls short, 6.2.3 Atom economy of a reaction, 6.2.4 Choosing a reaction pathway, and 6.2.5 Molar volume of gases and Avogadro's law. Each one has a worked solution and a mark scheme showing where the marks go.