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Question 18M.2.sl.TZ1.b.i

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Date May 2018 Marks available [Maximum mark: 1] Reference code 18M.2.sl.TZ1.b.i
Level sl Paper 2 Time zone TZ1
Command term Suggest Question number b.i Adapted from N/A
b.i.
[Maximum mark: 1]
18M.2.sl.TZ1.b.i

Calcium carbonate reacts with hydrochloric acid.

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

The results of a series of experiments in which the concentration of HCl was varied are shown below.

M18/4/CHEMI/SP2/ENG/TZ1/04.b

Suggest why point D is so far out of line assuming human error is not the cause.

[1]

Markscheme

reaction is fast at high concentration AND may be difficult to measure accurately

OR

so many bubbles of CO2 produced that inhibit contact of HCl(aq) with CaCO3(s)

OR

insufficient change in conductivity/pH at high concentrations

OR

calcium carbonate has been used up/is limiting reagent/there is not enough calcium carbonate «to react with the high concentration of HCl»

OR

HCl is in excess

OR

so many bubbles of CO2 produced that inhibit contact of HCl(aq) with CaCO3(s)

[1 mark]

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