DP Chemistry (last assessment 2024)

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Question 19M.3.sl.TZ1.c

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Date May 2019 Marks available [Maximum mark: 1] Reference code 19M.3.sl.TZ1.c
Level sl Paper 3 Time zone TZ1
Command term Calculate Question number c Adapted from N/A
c.
[Maximum mark: 1]
19M.3.sl.TZ1.c

Uranium-235, 235U, is bombarded with a neutron causing a fission reaction.

The daughter product, 89Kr, has a half-life of 3.15 min.

Calculate the time required, in minutes, for the mass of 89Kr to fall to 6.25 % of its initial value.

[1]

Markscheme

«6.25 % = 4 half-lives, so 4 × 3.15 =» 12.6 «min»  [✔]

Examiners report

Another question that created far more problems than anticipated with only about half gaining the mark. Many students appeared not to realise that 6.25 % is 1/16, hence the amount remaining after 4 half lives.

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