Calculate the molar mass of the following:

(i) H2O (ii) CO2 (iii) CH4


(i) H2O

Atomic Mass of Hydrogen = 1g


Atomic Mass of Oxygen = 16g


From the molecular formula of water, it is understood that in 1 mole of water, 2 moles of hydrogen and 1 mole of oxygen is present.


So Molecular Mass of Water = [2×1] + [16×1]


= 2 + 16


= 18g


Therefore, the molecular mass of water is 18g


(ii) CO2


Atomic Mass of Carbon = 12g


Atomic Mass of Oxygen = 16g


From the molecular formula of carbon dioxide, it is understood that in 1 mole of carbon dioxide, 1 mole of carbon and 2 moles of oxygen is present.


So Molecular Mass of Carbon Dioxide = [12×1] + [16×2]


= 12 + 32


= 44g


Therefore, the molecular mass of carbon dioxide is 44g


(iii) CH4


Atomic Mass of Carbon = 12g


Atomic Mass of Hydrogen = 1g


From the molecular formula of methane, it is understood that in 1 mole of methane, 1 mole of carbon and 4 moles of hydrogen is present.


So Molecular Mass of Methane = [12×1] + [4×1]


= 12 + 4


= 16g


Therefore, the molecular mass of methane is 16g


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