Question

Choose the correct statements from the following:
A. \( Mn_2O_7 \) is an oil at room temperature
B. \( V_2O_4 \) reacts with acid to give \( VO_2^{2+} \)
C. \( CrO \) is a basic oxide
D. \( V_2O_5 \) does not react with acid
Choose the correct answer from the options given below:

• A. A, B and D only
• B. A and C only
• C. A, B and C only
• D. B and C only

Answer 1

The Correct Option is B

Let’s analyze each statement individually:

Statement A: \( \text{Mn}_2\text{O}_7 \) is an oil at room temperature. - \( \text{Mn}_2\text{O}_7 \) (manganese heptoxide) is indeed a dark green oil that is highly unstable and explosive at room temperature. It is a covalent oxide and behaves as an acidic oxide due to its high oxidation state. Therefore, this statement is correct.

Statement B: \( \text{V}_2\text{O}_4 \) reacts with acid to give \( \text{VO}_2^{2+} \). - \( \text{V}_2\text{O}_4 \) (vanadium(IV) oxide) is an amphoteric oxide. It can react with acids, undergoing oxidation, to form the \( \text{VO}_2^{2+} \) ion (vanadyl ion). This reaction occurs as:

\[ \text{V}_2\text{O}_4 + 2\text{H}^+ \to 2\text{VO}_2^{2+} + \text{H}_2\text{O} \]

Therefore, this statement is also correct.

Statement C: \( \text{CrO} \) is a basic oxide. - \( \text{CrO} \) (chromium(II) oxide) is a basic oxide. It reacts readily with acids to form salts and water. For example:

\[ \text{CrO} + 2\text{HCl} \to \text{CrCl}_2 + \text{H}_2\text{O} \]

This confirms that \( \text{CrO} \) behaves as a basic oxide, so this statement is correct.

Statement D: \( \text{V}_2\text{O}_5 \) does not react with acid. - \( \text{V}_2\text{O}_5 \) (vanadium(V) oxide) is an amphoteric oxide, meaning it can react with both acids and bases. In fact, \( \text{V}_2\text{O}_5 \) can react with acidic solutions, such as hydrochloric acid, and undergo reduction. Therefore, this statement is incorrect.

Since statements A and C are correct, the correct answer is Option (2).