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: Calculate the molecular mass of \( \text{Na}_2\text{SO}_4 \)
The molecular mass of a compound is the sum of the atomic masses of its elements. 
- Atomic mass of sodium (Na) = 23 g/mol, 
- Atomic mass of sulfur (S) = 32 g/mol, 
- Atomic mass of oxygen (O) = 16 g/mol. 
Step 2: Add the atomic masses
The molecular formula of sodium sulfate is \( \text{Na}_2\text{SO}_4 \), 
which contains: - 2 sodium atoms, - 1 sulfur atom, - 4 oxygen atoms. 
Thus, the molecular mass is: \[ \text{Molecular mass of Na}_2\text{SO}_4 = 2 \times 23 + 1 \times 32 + 4 \times 16 \] \[ = 46 + 32 + 64 = 142 \, \text{g/mol} \] 
Answer:
Therefore, the molecular mass of \( \text{Na}_2\text{SO}_4 \) is \( 142 \, \text{g/mol} \). So, the correct answer is option (1).