Comparing the rates of hydrolysis reactions (6.3 2)

Question 1

Instead of adding water

Answer 1

silver nitrate solution is added so the progress of the reaction can be followed. silver ions react with halide ions to give a precipitate
Ag+ + X- =AgX

Question 2

How to compare

Answer 2

Using ethanol as the solvent of the mixture (halogen alkanes and aqueous silver nitrate do not mix but form separate layers)
controlling variables such as temperature and concentration and quantity of halogenoalkanes
timing the appearance of the precipitate (difficult to do as may first appear faint and then become thicker with time )

Question 3

Two types of comparison that can be made

Answer 3

compare halogenalkanes with the same structure but different halogens
compare halogenalkanes with the same halogen but with different structures

Question 4

Fluoroalkanes

Answer 4

comparatively very unreactive so reactions involving them are often omitted

Question 5

results

Answer 5

fastest:1-iodobutane
1-bromobutane
1-chlorobutane

Question 6

explanation of results

Answer 6

may think one with the most polar bond would be the fastest to be hydrolyses because positive charge strongest so attacking nucleophile would be attracted more strongly (e.g. chlorine)
This is true but bond breaking requires energy and weaker bonds break more easily than strong C-I weakest and C-Cl strongest
So C-I bond breaks the easiest form I- ions and so the precipitate AgI forms more quickly

Question 7

c-f

Answer 7

much stronger than any others so explains why fluoroalkanes are often not used

Question 8

Results different structures

Answer 8

Fastest tertiary
secondary
primary
explanation next year