DP Physics (last assessment 2024)

Test builder »

Question 20N.2.SL.TZ0.c(iii)

Date	November 2020	Marks available	[Maximum mark: 2]	Reference code	20N.2.SL.TZ0.c(iii)
Level	SL	Paper	2	Time zone	TZ0
Command term	Calculate	Question number	c(iii)	Adapted from	N/A

c(iii).

[Maximum mark: 2]

20N.2.SL.TZ0.c(iii)

A sample of waste produced by the reactor contains $1.0 kg$ of strontium-94 (Sr-94). Sr-94 is radioactive and undergoes beta-minus ( $β^{-}$ ) decay into a daughter nuclide X. The reaction for this decay is

${}_{38}^{94}{Sr} \to X + {\bar{v}}_{e} + e$ .

The graph shows the variation with time of the mass of Sr-94 remaining in the sample.

Calculate the mass of Sr-94 remaining in the sample after $10$ minutes.

[2]

Markscheme

ALTERNATIVE 1

$10 \min$ $= 8 t_{1 / 2}$ ✓

mass remaining $= 1.0 \times {(\frac{1}{2})}^{8} = 3.9 \times 10^{- 3} « kg »$ ✓

ALTERNATIVE 2

decay constant $= « \frac{\ln 2}{75} = » 9.24 \times 10^{- 3} « s^{- 1} »$ ✓

mass remaining $= 1.0 \times e^{- 9.24 \times 10^{- 3} \times 600} = 3.9 \times 10^{- 3} « kg »$ ✓

Syllabus sections

Core » Topic 7: Atomic, nuclear and particle physics » 7.1 – Discrete energy and radioactivity

Core » Topic 7: Atomic, nuclear and particle physics