Which of the following metals does not dissolve in concentrated `HNO_(3)` ?

Options

A. Cr
B. Zn
C. Al
D. Both 1 and 3

Answer

To determine which of the following metals does not dissolve in concentrated HNO₃, we need to analyze the behavior of each metal when exposed to concentrated nitric acid.

### Step-by-Step Solution:

1. **Identify the Metals**: The metals given in the options are:
- Chromium (Cr)
- Zinc (Zn)
- Aluminum (Al)
- Both Chromium and Aluminum

2. **Understand the Reaction with Concentrated HNO₃**:
- Concentrated nitric acid (HNO₃) is a strong oxidizing agent and can react with many metals.

3. **Analyze Each Metal**:
- **Chromium (Cr)**:
- Chromium does not dissolve in concentrated HNO₃ due to the formation of a passive film of chromium oxide on its surface. This oxide layer prevents further reaction with the acid.
- **Zinc (Zn)**:
- Zinc readily dissolves in concentrated HNO₃, forming zinc nitrate (Zn(NO₃)₂) and releasing hydrogen gas.
- **Aluminum (Al)**:
- Aluminum also dissolves in concentrated HNO₃, forming aluminum nitrate (Al(NO₃)₃) and releasing hydrogen gas.
- **Both Chromium and Aluminum**:
- This option suggests that both metals do not dissolve, but we have established that aluminum does dissolve.

4. **Conclusion**:
- The only metal from the options that does not dissolve in concentrated HNO₃ is **Chromium (Cr)**.

### Final Answer:
**Chromium (Cr)** does not dissolve in concentrated HNO₃.