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5.1 Monitoring chemical reactions

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Question 7

A technician mixes 6.64 g of potassium iodide with excess lead nitrate solution. Lead iodide forms and is collected by filtration.

Pb(NO3)2+2KI→PbI2+2KNO3 \mathrm{Pb(NO_{3})_{2} + 2KI \rightarrow PbI_{2} + 2KNO_{3}} Pb(NO3​)2​+2KI→PbI2​+2KNO3​

The mass of lead iodide collected is 9.68 g.

Relative formula mass (MrM_rMr​): KI\mathrm{KI}KI = 166.0 PbI2\mathrm{PbI_{2}}PbI2​ = 461.0

a.

Calculate the percentage yield of lead iodide.

[3]
b.

Suggest one reason why the calculated percentage yield is greater than 100%.

[1]
Markscheme

5.1 Monitoring chemical reactions Questions

  1. GCSE
  2. /Chemistry
  3. /5.1 Monitoring chemical reactions

152 exam-style questions on OCR GCSE Chemistry 5.1 Monitoring chemical reactions, covering 5.1.1 The technique of titration, 5.1.2 Theoretical mass, percentage yield and atom economy, 5.1.3 Concentration of a solution in mol/dm3, 5.1.4 Concentration calculations and titration results, 5.1.5 Molar gas volume and volumes of gases in reactions, and 5.1.6 Choosing a reaction pathway. Each one has a worked solution and a mark scheme showing where the marks go.

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