Question

What is the % composition by mass of sulfur in sulfate, SO4-2?
Group of answer choices

33%

25%

50%

66%

Answer 1

To find the percentage composition by mass of sulfur in the sulfate ion (\(SO_4^{2-}\)), we first need to calculate the molar mass of the sulfate ion.

1. **Determine the atomic masses**:
- Sulfur (S) has an atomic mass of approximately 32.07 g/mol.
- Oxygen (O) has an atomic mass of approximately 16.00 g/mol.

2. **Calculate the molar mass of sulfate**:
- The sulfate ion has 1 sulfur atom and 4 oxygen atoms.
- Molar mass of \(SO_4^{2-} = 1 \times 32.07\, \text{g/mol (S)} + 4 \times 16.00\, \text{g/mol (O)}\)
- Molar mass of \(SO_4^{2-} = 32.07\, \text{g/mol} + 64.00\, \text{g/mol} = 96.07\, \text{g/mol}\)

3. **Calculate the percentage composition of sulfur**:
- Percentage of sulfur \( = \left( \frac{\text{mass of sulfur}}{\text{molar mass of sulfate}} \right) \times 100\)
- Percentage of sulfur \( = \left( \frac{32.07\, \text{g/mol}}{96.07\, \text{g/mol}} \right) \times 100\)
- Percentage of sulfur \( \approx 33.4\% \)

Based on this calculation, the closest answer from the options provided is **33%**.