Chemistry 2008 JAMB Past Questions - Question 40: If the silver mirror test is positive, it indicates thfe presence of an

Correct Answer

D

Explanation

Out of the options you provided, only **alkanal** would give a positive result in the silver mirror test. Let's see why:

**Silver mirror test:** This test relies on the oxidation of a carbonyl group (C=O) to a carboxylic acid by an ammoniacal silver nitrate solution. The reduced silver ions form a shiny silver mirror on the inner surface of the reaction vessel.

**Applicability to different functional groups:**

* **Alkyne:** Alkynes do not have a carbonyl group and hence will not react in the silver mirror test.
* **Alkanol:** Alcohols also lack a carbonyl group and cannot be oxidized to carboxylic acids.
* **Alkanone:** While ketones also possess a carbonyl group, they are not reactive enough towards the silver mirror test conditions.
* **Alkanal:** Alkanals (aldehyde) readily give a positive test due to the presence of the highly reactive aldehyde group (R-CHO).

Therefore, a positive silver mirror test **indicates the presence of an alkanal**.

It's important to note that other functional groups with easily oxidizable aldehydic or similar structures might also react in this test. However, based on the options provided, only alkanal is the correct answer.