DP Chemistry (first assessment 2025)

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Question 20N.1A.SL.TZ0.28

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.1A.SL.TZ0.28
Level	SL	Paper	1A	Time zone	TZ0
Command term	Solve	Question number	28	Adapted from	N/A

28.

[Maximum mark: 1]

20N.1A.SL.TZ0.28

A student obtained the following data to calculate $q$ , using $q = m c Δ T$ .

$m = 20.2 g \pm 0.2 g$

$∆ T = 10 ° C \pm 1 ° C$

$c = 4.18 J g^{- 1} K^{- 1}$

What is the percentage uncertainty in the calculated value of $q$ ?

A. $0.2$

B. $1.2$

C. $11$

D. $14$

[1]

Markscheme

C

Examiners report

Just over ½ of the candidates could propagate uncertainties from absolute to relative.

Syllabus sections

Reactivity 1. What drives chemical reactions? » Reactivity 1.1—Measuring enthalpy changes » Reactivity 1.1.4—The standard enthalpy change for a chemical reaction, ΔH⦵, refers to the heat transferred at constant pressure under standard conditions and states. It can be determined from the change in temperature of a pure substance. Apply the equations Q = mcΔT and ΔH = − Qn in the calculation of the enthalpy change of a reaction.