DP Chemistry (last assessment 2024)

Question 19M.2.hl.TZ2.3b(ii)

Date	May 2019	Marks available	[Maximum mark: 2]	Reference code	19M.2.hl.TZ2.3b(ii)
Level	hl	Paper	2	Time zone	TZ2
Command term	Calculate	Question number	b(ii)	Adapted from	N/A

b(ii).

[Maximum mark: 2]

19M.2.hl.TZ2.3b(ii)

Dinitrogen monoxide, N₂O, causes depletion of ozone in the stratosphere.

Different sources of N₂O have different ratios of ¹⁴N : ¹⁵N.

(b(ii))

A sample of gas was enriched to contain 2 % by mass of ¹⁵N with the remainder being ¹⁴N.

Calculate the relative molecular mass of the resulting N₂O.

[2]

Markscheme

« $\frac{{(98 \times 14) + (2 \times 15)}}{{100}}$ =» 14.02 [✔]

«M_r = (14.02 × 2) + 16.00 =» 44.04 [✔]

Examiners report

Most candidates were able to calculate the accurate mass of N₂O, though quite a few candidates just calculated the mass of N and didn’t apply it to N₂O, losing an accessible mark.

Syllabus sections

Core

Core » Topic 2: Atomic structure » 2.1 The nuclear atom

Core » Topic 1: Stoichiometric relationships » 1.2 The mole concept

Core » Topic 1: Stoichiometric relationships

Core » Topic 2: Atomic structure

Question 19M.2.hl.TZ2.3b(ii)

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