206 g of molten sodium bromide is electrolysed. The maximum mass of sodium obtained will be : [Na = 23 u, Br = 80 u]

Question

Accepted Answer

To determine the maximum mass of sodium obtained from the electrolysis of 206 g of molten sodium bromide (NaBr), we need to follow these steps:

1. **Calculate the Molar Mass of NaBr:**
   - Sodium (Na) has an atomic mass of 23 u.
   - Bromine (Br) has an atomic mass of 80 u.
   - Therefore, the molar mass of NaBr = 23 u + 80 u = 103 g/mol.

2. **Determine the Moles of NaBr:**
   - Given mass of NaBr = 206 g.
   - Moles of NaBr = mass / molar mass = 206 g / 103 g/mol = 2 moles.

3. **Electrolysis Reaction:**
   - The electrolysis of NaBr results in the formation of sodium (Na) and bromine (Br2).
   - The balanced equation for the electrolysis of NaBr is:
     $$
     2 \text{NaBr} \rightarrow 2 \text{Na} + \text{Br}_2
     $$
   - From the equation, 2 moles of NaBr produce 2 moles of Na.

4. **Calculate the Mass of Sodium Produced:**
   - Moles of Na produced = 2 moles (from the stoichiometry of the reaction).
   - Molar mass of Na = 23 g/mol.
   - Mass of Na = moles × molar mass = 2 moles × 23 g/mol = 46 g.

Therefore, the maximum mass of sodium that can be obtained from the electrolysis of 206 g of NaBr is 46 g. This supports Option 2 as the correct answer.

**Explanation for Incorrect Options:**

- **Option 1 (40 g):** This option is incorrect because it underestimates the mass of sodium produced. The stoichiometry and calculations clearly show that 46 g of sodium is produced, not 40 g.

- **Option 3 (52 g):** This option is incorrect because it overestimates the mass of sodium produced. The calculations based on the balanced chemical equation and molar masses show that only 46 g of sodium can be obtained.

- **Option 4 (23 g):** This option is incorrect because it represents the mass of sodium from only 1 mole of NaBr, not the 2 moles present in 206 g of NaBr. The correct calculation for 2 moles results in 46 g of sodium.

In conclusion, the correct answer is Option 2, which accurately reflects the maximum mass of sodium obtained from the electrolysis of 206 g of sodium bromide.