Question

Which of following observations is found in Tollens test for aldehydes?

• A. The formation of pink or magenta color upon the addition of the reagent to the sample solution.
• B. Formation of an Ag layer on sides of test tube upon addition and warming of the reagent.
• C. Formation of brick-red precipitate upon heating with reagent.
• D. Appearance of red color upon shaking with reagent.

Hint:

Tollens reagent deposits a silver mirror with aldehydes on warming.

Answer 1

The Correct Option is B

Step 1: Reagent:
Silver nitrate plus ammonia gives the diammine silver(I) complex.

Step 2: Reaction:
The aldehyde group is oxidised to carboxylate and $\text{Ag}^+$ is reduced to $\text{Ag}$.

Step 3: Observation:
Bright silver metal coats the glass, called the silver mirror. This is option (B).

Final Answer:
A silver mirror forms on the tube wall. \[ \boxed{\text{(B) }\text{Ag layer on the test tube}} \]