A Level Chemistry 2017 Paper 1 Question 23 Solution - Exclusive

In this exclusive video we want to discuss the suggested solution for A Levels Chemistry (H2 Chemistry) 2017 Paper 1 Question 23.

Let's take a look at this question:

2017 A Level H2 Chemistry P1 Q23 question

The concept tested in this question is on the reactivity of C-X bonds in Halogenoalkanes.

For a list of all the reactions of halogenalkanes, do check out this video lesson.

When silver nitrate is used in organic chemistry questions, we are testing for the presence of sliver halide precipitates, where the halides are released from nucleophilic substitution reactions of halogenoalkanes or alkylhalides.

Observation 1 - No precipitate formed in 2 of the tubes

When no precipitate is formed, it means the C-X bond is stable and resistant to nucleophilic substitution.

Halogenobenzene will give this observation as the lone pair of halogen can interact with the delocalised pi system of benzene and the C-X bond is stablised by resonance which makes it unreactive.

2017 A Level H2 Chemistry P1 Q23 compare chlorobenzene and bromobenzene reactivity

Hence compounds W and Y will not form a precipitate, and options A and B are eliminated.

2017 A Level H2 Chemistry P1 Q23 determine which compounds with no ppt

Observation 2 - Precipitate formed at different speeds

Comparing choloroalkane X and iodoalkane Z, the C-I bond in Z is longer and weaker hence is more easily broken to release I- for precipitation.

2017 A Level H2 Chemistry P1 Q23 compare chloroalkane and iodoalkane reactivity

This means the formation of yellow AgI precipitate will be faster as compared to the formation of white AgCl precipitate, and option C is eliminated.

2017 A Level H2 Chemistry P1 Q23 determine which ppt forms the fastest

Therefore the answer to this question will be option D.

Check out this video for the full solution and detailed explanation!

Topic: Halogenoalkanes, Organic Chemistry, A Level Chemistry, Singapore

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