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

Answer: (B)

A and C only

Answer 2

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).