Arrange the pairs in sequence in decreasing order of basicity of an acid and acidity of a base followed by the normal salts formed by the given acid-base pairs in the same order, respectively.
(1) acetic acid and ammonium hydroxide
(2) oxalic acid and barium hydroxide
(3) phosphoric acid and aluminium hydroxide.
(4) barium oxalate
(5) ammonium acetate
(6) aluminium phosphate

Options

A. 14365
B. 321645
C. 143526
D. 341526

Answer

To solve the question, we need to arrange the given acid-base pairs in decreasing order of basicity of the acids and acidity of the bases, followed by the normal salts formed by these pairs. Let's go through the steps systematically.

### Step 1: Identify the Acids and Bases
The pairs given are:
1. Acetic acid (CH₃COOH) and ammonium hydroxide (NH₄OH)
2. Oxalic acid (C₂H₂O₄) and barium hydroxide (Ba(OH)₂)
3. Phosphoric acid (H₃PO₄) and aluminium hydroxide (Al(OH)₃)

### Step 2: Determine the Basicity of the Acids
Basicity of an acid refers to the number of hydrogen ions (H⁺) it can donate. The acids can be ranked as follows:
- **Phosphoric acid (H₃PO₄)**: Triprotic (can donate 3 H⁺)
- **Oxalic acid (C₂H₂O₄)**: Diprotic (can donate 2 H⁺)
- **Acetic acid (CH₃COOH)**: Monoprotic (can donate 1 H⁺)

Thus, the order of decreasing basicity of the acids is:
1. Phosphoric acid
2. Oxalic acid
3. Acetic acid

### Step 3: Determine the Acidity of the Bases
Acidity of a base refers to its ability to accept protons (H⁺). The bases can be ranked as follows:
- **Aluminium hydroxide (Al(OH)₃)**: Weak base
- **Barium hydroxide (Ba(OH)₂)**: Strong base
- **Ammonium hydroxide (NH₄OH)**: Weak base

Thus, the order of decreasing acidity of the bases is:
1. Barium hydroxide
2. Ammonium hydroxide
3. Aluminium hydroxide

### Step 4: Combine the Orders
Now we combine the orders of the acids and bases:
1. **Phosphoric acid (H₃PO₄)** with **Aluminium hydroxide (Al(OH)₃)**
2. **Oxalic acid (C₂H₂O₄)** with **Barium hydroxide (Ba(OH)₂)**
3. **Acetic acid (CH₃COOH)** with **Ammonium hydroxide (NH₄OH)**

### Step 5: Identify the Normal Salts Formed
Now we identify the normal salts formed by these acid-base pairs:
1. **Phosphoric acid + Aluminium hydroxide** → **Aluminium phosphate (AlPO₄)**
2. **Oxalic acid + Barium hydroxide** → **Barium oxalate (BaC₂O₄)**
3. **Acetic acid + Ammonium hydroxide** → **Ammonium acetate (NH₄C₂H₃O₂)**

### Step 6: Final Arrangement
Now we arrange the pairs in the order of the acids and bases followed by their respective salts:
1. **Phosphoric acid** - **Aluminium hydroxide** - **Aluminium phosphate**
2. **Oxalic acid** - **Barium hydroxide** - **Barium oxalate**
3. **Acetic acid** - **Ammonium hydroxide** - **Ammonium acetate**

Thus, the final sequence is:
1. Phosphoric acid (3)
2. Oxalic acid (2)
3. Acetic acid (1)
4. Aluminium phosphate (6)
5. Barium oxalate (4)
6. Ammonium acetate (5)

### Final Answer
The final order is: **3, 2, 1, 6, 4, 5**.