DP Chemistry (last assessment 2024)
Question 18M.3.hl.TZ2.26b
| Date | May 2018 | Marks available | [Maximum mark: 2] | Reference code | 18M.3.hl.TZ2.26b |
| Level | hl | Paper | 3 | Time zone | TZ2 |
| Command term | Calculate | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 2]
18M.3.hl.TZ2.26b
Radioisotopes can be used to treat a wide variety of diseases.
(b)
The half-life of phosphorus-32 is 14.3 days. Calculate the mass, in g, of 32P remaining after 57.2 days if the initial sample contains 2.63 × 10−8 mol. Use table 1 of the data booklet and Mr = 31.97 g mol−1.
[2]
Markscheme
ALTERNATIVE 1
«λ = =» 0.04847 «day–1»
«m(32P) = 2.63 × 10–8 mol × 31.97 g mol–1 × e–0.04847 × 57.2 =» 5.26 × 10–8 «g»
ALTERNATIVE 2
« =» 4 «half-lives passed»
OR
«n(32P) = =» 1.64 × 10–9 «mol»
«m(32P) = 1.64 × 10–9 mol × 31.97 g mol–1 =» 5.26 × 10–8 «g»
Award [2] for correct final answer.
Accept any value in the range “5.24–5.26 × 10–8 «g»”.
[2 marks]
