Example 1: How many moles are there in 18g of carbon?

\(\text{Using the triangle on the previous slide, Moles =} \frac{Mass}{\text{Formula mass}}\)

\(\text{Therefore, }\frac{18}{12}=1.5moles\)

Example 2: How many grams are there in 4.5 moles of calcium carbonate?

\(Mass = Moles \times \text{Formula mass}\)

\(\text{So, Mass = 4.5} \times 100 = 450g\)

Example 2: 3 moles of an element has a mass of 21g. What is the element?

\(\text{Formula mass =} \frac{Mass}{\text{Moles}}\)

\(\text{Therefore, the element has an atomic mass of 7g. It is lithium.}\)