A Level Chemistry 2017 Paper 1 Question 25 Solution - Exclusive

In this exclusive video we want to discuss the suggested solution for A Levels Chemistry (H2 Chemistry) 2017 Paper 1 Question 25.

Let's take a look at this question:

2017 A Level H2 Chemistry P1 Q25 question

The topic tested in this question is on the acidity of organic compounds carboxylic acid, phenol and alcohol.

The acidity and reactions of these compounds with bases are as summarised in the table below:

2017 A Level H2 Chemistry P1 Q25 acidity of organic compounds

From the table we know that:

- carboxylic acid is the strongest acid and can react with Na, NaOH and Na2CO3
- phenol is less acidic and can react with Na and NaOH only
- alcohol is the least acidic and can only react with Na

We must always remember that alcohol is a weaker acid than water so therefore alcohols are neutral and cannot react with bases like NaOH and Na2CO3.

So we can now conclude that mandelic acid will react with 2 moles of Na due to one carboxylic acid and alcohol functional group.

2017 A Level H2 Chemistry P1 Q25 mandelic acid

Saligenin will react with 1 mole of NaOH due to one phenol functional group. Remember alcohol will not react with NaOH since it is neutral.

2017 A Level H2 Chemistry P1 Q25 saligenin

Finally we can compare the options and decide that the answer to this question is D.

2017 A Level H2 Chemistry P1 Q25 compare options

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

Topic: Acidity of Organic Compounds, Organic Chemistry, A Level Chemistry, Singapore

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