Be and Al exhibit diagonal relationship. Which of the following statements about them is/are not true?
(i) both react with HCl to liberate `H_(2)`.
(ii) Theey are made passive by `HNO_(3)`.
(iii) Their carbides give acetylene on treatment with water.
(iv) Their oxides are amphoteric.

Options

A. (iii) and (iv)
B. (i) and (iii)
C. (i) only
D. (iii) only

Explanation

To determine which statements about Beryllium (Be) and Aluminum (Al) are not true, we will analyze each statement one by one.

### Step 1: Analyze Statement (i)
**Statement (i):** Both react with HCl to liberate H₂.

- **Beryllium Reaction:**
\[ \text{Be} + 2 \text{HCl} \rightarrow \text{BeCl}_2 + \text{H}_2 \]
Beryllium reacts with hydrochloric acid to produce beryllium chloride and hydrogen gas.

- **Aluminum Reaction:**
\[ 2 \text{Al} + 6 \text{HCl} \rightarrow 2 \text{AlCl}_3 + 3 \text{H}_2 \]
Aluminum also reacts with hydrochloric acid to produce aluminum chloride and hydrogen gas.

**Conclusion:** This statement is true.

### Step 2: Analyze Statement (ii)
**Statement (ii):** They are made passive by HNO₃.

- **Explanation:**
Nitric acid (HNO₃) is a strong oxidizing agent. It oxidizes both beryllium and aluminum, forming a protective oxide layer on their surfaces, which prevents further reaction.

**Conclusion:** This statement is true.

### Step 3: Analyze Statement (iii)
**Statement (iii):** Their carbides give acetylene on treatment with water.

- **Beryllium Carbide Reaction:**
\[ \text{Be}_2\text{C} + 4 \text{H}_2\text{O} \rightarrow 2 \text{Be(OH)}_2 + \text{CH}_4 \]
Beryllium carbide reacts with water to produce beryllium hydroxide and methane (not acetylene).

- **Aluminum Carbide Reaction:**
\[ \text{Al}_4\text{C}_3 + 12 \text{H}_2\text{O} \rightarrow 4 \text{Al(OH)}_3 + 3 \text{CH}_4 \]
Aluminum carbide also reacts with water to produce aluminum hydroxide and methane (not acetylene).

**Conclusion:** This statement is not true.

### Step 4: Analyze Statement (iv)
**Statement (iv):** Their oxides are amphoteric.

- **Beryllium Oxide (BeO):**
BeO can react with both acids and bases.

- **Aluminum Oxide (Al₂O₃):**
Al₂O₃ also exhibits amphoteric behavior, reacting with both acids and bases.

**Conclusion:** This statement is true.

### Final Conclusion
The only statement that is not true is statement (iii). Therefore, the answer is that statement (iii) is the only one that is not true.

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