DP Chemistry (first assessment 2025)

Question 20N.1B.SL.TZ0.2d

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.1B.SL.TZ0.2d
Level	SL	Paper	1B	Time zone	TZ0
Command term	Outline	Question number	d	Adapted from	N/A

[Maximum mark: 1]

20N.1B.SL.TZ0.2d

(d)

An additional experiment was conducted in which only the sulfuric acid catalyst was titrated with $NaOH (aq)$ . Outline why this experiment was necessary.

[1]

Markscheme

to determine volume/moles of $NaOH$ used up by the catalyst/sulfuric acid «in the titration»
OR
to eliminate/reduce «systematic» error caused by acid catalyst ✔

Do not accept “control” OR “standard” alone.

Examiners report

Some students achieved on mark. Many answers referred simple to "control" or "standard" underlining the lack of some skills as also identified in the Internal assessment. Once again very few students had the specific details necessary to explain why this separate titration was needed in their response to receive a mark.

Syllabus sections

Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.1—Proton transfer reactions » Reactivity 3.1.7—Acids react with bases in neutralization reactions. Formulate equations for the reactions between acids and metal oxides, metal hydroxides, hydrogencarbonates and carbonates.

Tools » Tool 1: Experimental techniques

Question 20N.1B.SL.TZ0.2d

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Syllabus sections

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