A : Benzaldehydes do not give possitive ...

A : Benzaldehydes do not give possitive Fehling test
R : Aldehydes give positive Tollen's test.

If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).

If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).

If Assertion is true statement but Reason is false, then mark (3).

If both Assertion and Reason are false statements, then mark (4).

Text Solution

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The correct Answer is:

To solve the question, we need to analyze the statements given and determine their validity based on the chemistry of benzaldehyde and the tests mentioned. ### Step-by-Step Solution: 1. **Understanding the Statements**: - Statement A: "Benzaldehydes do not give positive Fehling test." - Statement R: "Aldehydes give positive Tollen's test." 2. **Analyzing Statement A**: - The Fehling test is used to differentiate between reducing and non-reducing sugars and also to test for aldehydes. It involves the reduction of copper(II) ions to copper(I) oxide, which appears as a red precipitate. - Benzaldehyde (C6H5CHO) is an aromatic aldehyde. Aromatic aldehydes do not have an alpha hydrogen atom, which is necessary for the reaction to occur in the Fehling test. - Since benzaldehyde lacks an alpha hydrogen, it does not undergo oxidation in the Fehling test, thus it does not give a positive result. 3. **Analyzing Statement R**: - The Tollen's test involves the use of ammoniacal silver nitrate, which reduces to metallic silver in the presence of aldehydes. - Aldehydes, including both aliphatic and aromatic aldehydes (like benzaldehyde), can reduce Tollen's reagent and thus give a positive result. - Therefore, the statement that "Aldehydes give positive Tollen's test" is correct. 4. **Conclusion**: - Both statements A and R are true. However, the reason (R) does not correctly explain the observation (A) because the lack of a positive Fehling test for benzaldehyde is due to the absence of alpha hydrogen, not because aldehydes in general give a positive Tollen's test. - Therefore, the correct option is that both statements are true, but the reason is not a correct explanation of the statement. ### Final Answer: Both statements are true, but the reason is not a correct explanation of the statement.