Question

If the mass of one mole of hydrogen is 1.01 grams; phosphorus, 30.97 grams; and oxygen, 16.0 grams, what is the molar mass of phosphoric acid (H3PO4)?

A.
50.0 grams

B.
66.0 grams

C.
82.0 grams

D.
98.0 grams

Answer 1

To calculate the molar mass of phosphoric acid (H₃PO₄), we need to sum the molar masses of all the atoms in the formula.

- Hydrogen (H): 3 atoms × 1.01 g/mol = 3.03 g/mol
- Phosphorus (P): 1 atom × 30.97 g/mol = 30.97 g/mol
- Oxygen (O): 4 atoms × 16.0 g/mol = 64.0 g/mol

Now, add these values together:

\[
3.03 \, \text{g/mol (H)} + 30.97 \, \text{g/mol (P)} + 64.0 \, \text{g/mol (O)} = 98.0 \, \text{g/mol}
\]

Therefore, the molar mass of phosphoric acid (H₃PO₄) is **98.0 grams**.

The correct answer is:

**D. 98.0 grams**