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
according to mole concept,
1 mole of oxygen=6.022*10 23 molecules =32g = 22.4l
where 32g is the gram molecular mass of an oxygen molecule
ie gram molecular mass of 1 O2 molecule =gram molecular mass of 1 oxygen atom * 2(because oxygen is a diatomic molecule.)
=16 g * 2
so,16g contain 6.022* 1023 molecules
so number of molecules in 8g of of oxygen gas= 6.022 * 1023 /32 *8
=1.505 * 1023 molecules.