DP Chemistry (first assessment 2025)

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Question 20N.1A.SL.TZ0.3

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.1A.SL.TZ0.3
Level	SL	Paper	1A	Time zone	TZ0
Command term	Determine	Question number	3	Adapted from	N/A

3.

[Maximum mark: 1]

20N.1A.SL.TZ0.3

Which of these molecular formulae are also empirical formulae?

$C_{2} H_{6} O$
$C_{2} H_{4} O_{2}$
$C_{5} H_{12}$

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

[1]

Markscheme

B

Examiners report

One of the best answered questions on paper 1. Very few of the candidates struggled with distinguishing molecular and empirical formula.

Syllabus sections

Structure 1. Models of the particulate nature of matter » Structure 1.4—Counting particles by mass: The mole » Structure 1.4.4—The empirical formula of a compound gives the simplest ratio of atoms of each element present in that compound. The molecular formula gives the actual number of atoms of each element present in a molecule. Interconvert the percentage composition by mass and the empirical formula. Determine the molecular formula of a compound from its empirical formula and molar mass.