DP Chemistry (last assessment 2024)

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Question 18M.2.hl.TZ1.d

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Date May 2018 Marks available [Maximum mark: 3] Reference code 18M.2.hl.TZ1.d
Level hl Paper 2 Time zone TZ1
Command term Describe Question number d Adapted from N/A
d.
[Maximum mark: 3]
18M.2.hl.TZ1.d

Calcium carbonate reacts with hydrochloric acid.

CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)

Describe how the activation energy of this reaction could be determined.

[3]

Markscheme

ALTERNATIVE 1:

carry out reaction at several temperatures

plot 1 T  against log rate constant

Ea = – gradient ×  R

 

ALTERNATIVE 2:

carry out reaction at two temperatures

 

determine two rate constants

OR

determine the temperature coefficient of the rate

 

use the formula  ln ⁡ k 1 k 2 = E a R ( 1 T 2 − 1 T 1 )

 

 

Accept “gradient = − E a R ” for M3.

Award both M2 and M3 for the formula   ln r a t e 1 r a t e 2 = E a R ( 1 T 2 − 1 T 1 ) .

Accept any variation of the formula, such as r a t e 1 r a t e 2 = e − E a R ( 1 T 1 − 1 T 2 ) .

[3 marks]

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