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

Considering the molar mass of 12-C is 12 grams, how many moles are in 48 grams of 12-C atoms?

1. 2 moles

2. 3 moles

3. 4 moles

4. 5 moles

The correct answer is: 4 moles

To determine the number of moles in a given mass of a substance, you can use the formula: \[ \text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \] In this case, the molar mass of carbon-12 (12-C) is given as 12 grams per mole. You have a mass of 48 grams of 12-C atoms. Applying the formula: \[ \text{Number of moles} = \frac{48 \text{ g}}{12 \text{ g/mol}} = 4 \text{ moles} \] Therefore, the correct choice is based on this calculation. In this context, if you have calculated it to yield 4 moles, that corresponds directly to the mass of 48 grams divided by the molar mass of 12 grams per mole. This reveals how moles measure the amount of substance and connect mass to the number of particles, reinforcing the fundamental concepts of stoichiometry in chemistry.