Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

What is the mass of one mole of water?

1. 16.00 g

2. 18.02 g

3. 20.18 g

4. 22.99 g

The correct answer is: 18.02 g

The mass of one mole of water is determined by the molar mass, which is calculated from the atomic masses of its constituent elements: hydrogen and oxygen. Water (H₂O) consists of two hydrogen atoms and one oxygen atom. The atomic mass of hydrogen is approximately 1.01 grams per mole, and since there are two hydrogen atoms in a water molecule, that contributes about 2.02 grams per mole from hydrogen. The atomic mass of oxygen is approximately 16.00 grams per mole. When these are combined, the calculation for the molar mass of water becomes: 2 × 1.01 g/mol (for hydrogen) + 16.00 g/mol (for oxygen) = 18.02 g/mol. Thus, the correct answer reflects the total mass of one mole of water, confirming that it is indeed 18.02 grams. This understanding is vital in fields like chemistry and health sciences, where precise measurements are important for reactions and medication dosages.