Question

What is the molecular mass of $ \text{Na}_2\text{SO}_4 $?

• A. \( 142 \, \text{g/mol} \)
• B. \( 120 \, \text{g/mol} \)
• C. \( 158 \, \text{g/mol} \)
• D. \( 98 \, \text{g/mol} \)

Hint:

Remember: To calculate the molecular mass, add the atomic masses of all the elements in the compound, considering the number of atoms of each element.

Answer 1

The Correct Option is A

Step 1: Determine the molecular mass of \( \text{Na}_2\text{SO}_4 \)
The molecular mass of a compound is the aggregate of the atomic masses of its constituent elements.
- Sodium (Na) atomic mass: 23 g/mol. 
- Sulfur (S) atomic mass: 32 g/mol. 
- Oxygen (O) atomic mass: 16 g/mol. 
Step 2: Sum the atomic masses
The molecular formula for sodium sulfate is \( \text{Na}_2\text{SO}_4 \), indicating the presence of: - 2 sodium atoms, - 1 sulfur atom, and - 4 oxygen atoms. 
Consequently, the molecular mass is calculated as: \[ \text{Molecular mass of Na}_2\text{SO}_4 = (2 \times 23) + (1 \times 32) + (4 \times 16) \] \[ = 46 + 32 + 64 = 142 \, \text{g/mol} \] 
Answer:
The molecular mass of \( \text{Na}_2\text{SO}_4 \) is \( 142 \, \text{g/mol} \). This corresponds to option (1).