Calculate the number of molecules in 8g of Oxygen ?
A molecule of oxygen consists of two atoms of oxygen, and is therefore denoted by O2. Thus, the molar mass of oxygen molecule is 16 X 2 = 32g. So, 32g of O2 consists of 6.022 X 1023 molecules of O2. Therefore
32g of O2 = 6.022 X 1023 molecules of O2
1g of O2 = (6.022 X 1023 / 32) molecules of O2
8g of of O2 = (6.022 X 1023 X 8) / 32 molecules of O2
= 1.506 X 1023 molecules of O2