Arrange the following pairs in a sequence of decreasing order of acidity of base and increasing order of basicity of an acid and the salts formed between an acid and base with equal basicity and acidity in their increasing order, respectively.
(1) sodium chloride.
(2) barium hydroxide and sulphuric acid
(3) ferric phosphate
(4) ferric hydroxide and hydrochloric acid
(5) barium sulphate
(6) sodium hydroxide and phosphoric acid

Options

A. 426153
B. 624153
C. 426351
D. 624351

Explanation

To solve the problem of arranging the given pairs in a sequence of decreasing order of acidity of bases and increasing order of basicity of acids, along with the salts formed, we will follow these steps:

### Step 1: Identify the Acids and Bases
- **Acids and Bases:**
1. Sodium chloride (NaCl) - salt
2. Barium hydroxide (Ba(OH)₂) and sulfuric acid (H₂SO₄) - base and acid
3. Ferric phosphate (FePO₄) - salt
4. Ferric hydroxide (Fe(OH)₃) and hydrochloric acid (HCl) - base and acid
5. Barium sulfate (BaSO₄) - salt
6. Sodium hydroxide (NaOH) and phosphoric acid (H₃PO₄) - base and acid

### Step 2: Determine the Acidity of Bases
- **Acidity of Bases (Decreasing Order):**
- Ferric hydroxide (Fe(OH)₃) is the least basic.
- Barium hydroxide (Ba(OH)₂) is more basic than Fe(OH)₃.
- Sodium hydroxide (NaOH) is the strongest base.

### Step 3: Determine the Basicity of Acids
- **Basicity of Acids (Increasing Order):**
- Hydrochloric acid (HCl) is a strong acid (low basicity).
- Sulfuric acid (H₂SO₄) has higher basicity than HCl.
- Phosphoric acid (H₃PO₄) has the highest basicity.

### Step 4: Arrange the Pairs
- **Arranging Acids and Bases:**
1. Ferric hydroxide and hydrochloric acid (Fe(OH)₃ + HCl) - 4
2. Barium hydroxide and sulfuric acid (Ba(OH)₂ + H₂SO₄) - 2
3. Sodium hydroxide and phosphoric acid (NaOH + H₃PO₄) - 6

### Step 5: Identify the Salts
- **Salts Formed:**
1. Sodium chloride (NaCl) - 1
2. Barium sulfate (BaSO₄) - 5
3. Ferric phosphate (FePO₄) - 3

### Step 6: Final Arrangement
- **Final Sequence:**
- For Acids and Bases: 4 (Fe(OH)₃ + HCl), 2 (Ba(OH)₂ + H₂SO₄), 6 (NaOH + H₃PO₄)
- For Salts: 1 (NaCl), 5 (BaSO₄), 3 (FePO₄)

### Complete Answer
The final arrangement is:
- **Acids and Bases:** 4, 2, 6
- **Salts:** 1, 5, 3