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Edexcel IAL Chemistry A2 6.P14 health and safety in practical work

Edexcel IAL Chemistry A2 6.P14 health and safety in practical work
Pearson Edexcel IAL Chemistry syllabusChemistry YCH11First assessment 2019

The questions reward specific hazard-control links: identify toxic, oxidising or corrosive risks, then choose gloves or a fume cupboard only when the context supports it.

How this is tested

  • Match hazard labels to toxic, oxidising or corrosive substances in practical contexts.
  • Choose gloves for corrosive skin-contact risks such as phenol or ethanoic acid.
  • Use a fume cupboard when nitrogen dioxide or other toxic fumes are produced.

Question 3

[Maximum number: 3]

\section*{3 Brass is an alloy of copper. The percentage by mass of copper in a sample of brass can be determined by a three-stage process. \\ Stage 1 Oxidation of the copper to copper(II) ions with excess concentrated nitric acid. \\ Stage 2 Reduction of the copper(II) ions to copper(I) ions with excess iodide ions. \\ Stage 3 Titration of the iodine produced in Stage 2 against a standard solution of sodium thiosulfate. be determined by a three-stage process. p \\ Oxidation of the copper to copper(II) ions with excess con \\ dide ions. Titration of the iodine produced in Stage 2 against a standard solution of sodited. 'கே九 SIII 3

Question 3(a)

(a)

\section*{3 Brass is an alloy of copper. The percentage by mass of copper in a sample of brass can be determined by a three-stage process. \\ Stage 1 Oxidation of the copper to copper(II) ions with excess concentrated nitric acid. \\ Stage 2 Reduction of the copper(II) ions to copper(I) ions with excess iodide ions. \\ Stage 3 Titration of the iodine produced in Stage 2 against a standard solution of sodium thiosulfate. be determined by a three-stage process. p \\ Oxidation of the copper to copper(II) ions with excess con \\ dide ions. Titration of the iodine produced in Stage 2 against a standard solution of sodited. 'கே九 SIII 3

[ 3 ]

Question 3(a)(i)

(i)

State two hazards in this experiment, giving the precautions you would take to minimise the risk associated with each hazard.
Assume safety spectacles and a laboratory coat are worn.

[ 2 ]

Question 3(a)(iii)

(ii)

Excess nitric acid must be neutralised before the iodide ions are added in Stage 2.

Sodium carbonate solution is slowly added to the cooled solution. The solution is neutralised when a faint precipitate appears.

Suggest why the solution is cooled before the addition of the sodium carbonate solution.

[ 1 ]