Calculate the number of molecules in 8g of Oxygen ?

A molecule of oxygen consists of two atoms of oxygen, and is therefore denoted by O_{2}. Thus, the molar mass of oxygen molecule is 16 X 2 = 32g. So, 32g of O_{2} consists of 6.022 X 10^{23} molecules of O_{2}. Therefore

32g of O_{2} = 6.022 X 10^{23} molecules of O_{2}

1g of O_{2} = (6.022 X 10^{23} / 32) molecules of O_{2}

8g of of O_{2} = (6.022 X 10^{23} X 8) / 32 molecules of O_{2}

= 1.506 X 10^{23} molecules of O_{2}

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