CAIE A-Level Chemistry AS 15.1.7 Rate of Hydrolysis of Halogenoalkanes Questions

Practise comparing halogenoalkane hydrolysis rates using C–X bond energies, aqueous silver nitrate observations and SN1 or SN2 pathways.

Exam points

rank C–I as fastest to hydrolyse, followed by C–Br and then stronger C–Cl
use time to form AgI, AgBr or AgCl precipitate as an experimental rate measure
explain slower chloroalkane hydrolysis by the greater energy needed to break C–Cl
link substrate structure and mechanism to the observed hydrolysis rate

[Maximum number: 2]

Halogenoalkanes react with a number of different reagents in nucleophilic substitution reactions.

Equal amounts of three different halogenoalkanes are added to three separate test-tubes. An equal amount of aqueous silver nitrate and ethanol is added to each test-tube. The time taken for a precipitate to form is recorded for each halogenoalkane.

Table for Question CAIE A-Level Chemistry AS 15.1.7 Rate of Hydrolysis of Halogenoalkanes Questions question 1 — CAIE A-Level Chemistry AS

Describe and explain the trend in reactivity of the different halogenoalkanes shown in this experiment.

M1 Increasing reactivity from $\mathrm{Cl} \rightarrow \mathrm{Br} \rightarrow \mathrm{I}$

M2 Due to decreasing strength of C-X bond (from C-Cl to C-Br to C-I )

OR

Less energy needed to break C-X (from C-Cl to C-Br to C-I )

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CAIE A-Level Chemistry AS 15.1.7 Rate of Hydrolysis of Halogenoalkanes Questions question 1