DP Chemistry (last assessment 2024)

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Question 18N.2.hl.TZ0.10

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Date November 2018 Marks available [Maximum mark: 4] Reference code 18N.2.hl.TZ0.10
Level hl Paper 2 Time zone TZ0
Command term Calculate, Classify, Deduce Question number 10 Adapted from N/A
10.
[Maximum mark: 4]
18N.2.hl.TZ0.10

The following mechanism is proposed for a reaction:

A + B → C + D        slow step
D + B → A + E        fast step

(a)

Classify substances B and D as reactant, product, catalyst, or intermediate, based on the proposed mechanism.

[2]

Markscheme

B: reactant ✔

D: intermediate ✔

(b)

Deduce the rate expression.

[1]

Markscheme

rate = k[A][B] ✔

(c)

Calculate the initial rate of reaction for experiment 2, if measured under the same conditions.

[1]

Markscheme

1.80 «mol dm–3 s–1» ✔

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