DP Chemistry (last assessment 2024)

Question 18M.3.hl.TZ1.14b.ii

Date	May 2018	Marks available	[Maximum mark: 3]	Reference code	18M.3.hl.TZ1.14b.ii
Level	hl	Paper	3	Time zone	TZ1
Command term	Explain	Question number	b.ii	Adapted from	N/A

b.ii.

[Maximum mark: 3]

18M.3.hl.TZ1.14b.ii

Modern electric cars store their energy in lithium ion batteries.

The carbon footprint of electric cars depends on how the electricity is produced. Nuclear fission of ²³⁵U is one source of electrical energy that has a minimal carbon footprint.

(b.ii)

Explain how the proportion of ²³⁵U in natural uranium is increased.

[3]

Markscheme

uranium converted to uranium hexafluoride/UF₆ gas

ALTERNATIVE 1:

gas «allowed to» diffuse

lower mass isotope/²³⁵U passes through more rapidly

ALTERNATIVE 2:

use of centrifuge

higher mass isotope/²³⁸U moves/closer to outside of centrifuge

lower mass isotope/²³⁵U stays in/removed from middle of centrifuge