Calculate the empirical and molecular formula of the compound having the following percentage composition :
Na = 36.5%, H = 0.8%, P = 24.6%, O = 38.1%
The molecular mass of the compound is 126 a.m.u. Also name the compound

Explanation

To solve the problem of finding the empirical and molecular formula of the compound with the given percentage composition, we will follow these steps:

### Step 1: Convert percentage composition to grams
Assume we have a 100 g sample of the compound. The mass of each element in grams will be equal to its percentage composition:
- Sodium (Na): 36.5 g
- Hydrogen (H): 0.8 g
- Phosphorus (P): 24.6 g
- Oxygen (O): 38.1 g

### Step 2: Convert grams to moles
Next, we will convert the mass of each element to moles using their respective atomic masses:
- Moles of Na = Mass of Na / Atomic mass of Na = 36.5 g / 23 g/mol = 1.587 moles
- Moles of H = Mass of H / Atomic mass of H = 0.8 g / 1 g/mol = 0.8 moles
- Moles of P = Mass of P / Atomic mass of P = 24.6 g / 31 g/mol = 0.794 moles
- Moles of O = Mass of O / Atomic mass of O = 38.1 g / 16 g/mol = 2.381 moles

### Step 3: Find the simplest mole ratio
To find the empirical formula, we need to divide all the mole values by the smallest number of moles calculated:
- Smallest number of moles = 0.794 (for P)
- Ratio for Na = 1.587 / 0.794 ≈ 2
- Ratio for H = 0.8 / 0.794 ≈ 1
- Ratio for P = 0.794 / 0.794 = 1
- Ratio for O = 2.381 / 0.794 ≈ 3

### Step 4: Write the empirical formula
From the ratios, we can write the empirical formula:
- Na: 2
- H: 1
- P: 1
- O: 3

Thus, the empirical formula is **Na₂HPO₃**.

### Step 5: Calculate the empirical formula mass
To confirm the empirical formula, we calculate its molar mass:
- Molar mass of Na₂HPO₃ = (2 × 23) + (1 × 1) + (1 × 31) + (3 × 16) = 46 + 1 + 31 + 48 = 126 g/mol.

### Step 6: Determine the molecular formula
Given that the molecular mass of the compound is 126 g/mol, we can find the molecular formula:
- Molecular mass / Empirical mass = 126 g/mol / 126 g/mol = 1.
- Therefore, the molecular formula is the same as the empirical formula: **Na₂HPO₃**.

### Step 7: Name the compound
The name of the compound Na₂HPO₃ is **sodium hydrogen phosphite**.

### Final Answers:
- **Empirical Formula**: Na₂HPO₃
- **Molecular Formula**: Na₂HPO₃
- **Name of the Compound**: Sodium hydrogen phosphite