How to convert grams to moles

Grams to Moles Formula :

Example-1 :How many moles of calcium atoms are in 20g of ca?

1mol ca = 40.08g

ca = 40.08gmol^-1

$$\frac{20\text{g}\;\text{ca}}{1}\;*\;\frac{1\text{mol}\;\text{ca}}{40.08\text{g}\;\text{ca}}\;=$$

$$0.499\text{mol}\;\text{ca}$$

Example-2 :How many moles of silicon atoms are in 150g of silicon Tetraflouride?

$$SiF_4\;=\;Si\;+\;4F$$

$$SiF_4\;=\;104.09\text{g}\;\text{mol}^{-1}$$

$$1\text{mol}\;SiF_4\;=\;104.09\text{g}\;SiF_4$$