CAIE A-Level Chemistry Practical Assessment Skills
Practise the experimental judgement, data handling and evaluation assessed in Paper 3 and Paper 5.
- Syllabus
- 2028–2030
- Course
- Chemistry 9701
- Level
- A2
Covered syllabus points
Practical assessment skills question 1
[Maximum number: 4]
The reaction between 1-chloro-1-phenylethane and hydroxide ions to produce 1-phenylethanol is:
C6H5CHClCH3+OH−→C6H5CH(OH)CH3+Cl−
1-chloro-1-phenylethane
1-phenylethanol
The rate of this reaction can be studied by measuring the amount of hydroxide ions that remain in solution at a given time. The reaction can effectively be stopped if the solution is diluted with an ice-cold solvent.
Describe a suitable method for studying the rate of this reaction at a temperature of 40∘C, given the following.
- a solution of 0.10 moldm−3 1-chloro-1-phenylethane, labelled A
- a solution of 0.10 moldm−3 sodium hydroxide, labelled B
- 0.10 moldm−3HCl
- volumetric glassware
- ice-cold solvent
- stopclock
- access to standard laboratory equipment and chemicals
Any of the three methods possible. Any 4 of the 5 points for each method available for maximum 4 marks.
Method 1
1 Ensure both solutions (A and B) at 40∘C before mixing
2 mix known volumes of A and B and start the clock
3 at known time take out a sample / X and add it to ice-cold solvent
4 titrate against HCl
5 repeat at time at known time intervals
Method 2
1 Ensure both solutions (A and B) at 40∘C before mixing
2 mix known volumes of A and B and start the clock
3 at known time pour into ice-cold solvent or pour ice-cold solvent in
4 titrate against HCl
5 repeat with different concentrations of either A or B, or repeat using different times
Method 3
1 Ensure both solutions (A and B) at 40∘C before mixing
2 mix known volumes of A and B and start the clock and add pH meter
3 at a known time . . . .
4 ... . record the pH
5 repeat pH readings at known time intervals
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