Convert the following into moles.(Atomic masses: 0 = 16u, H = 1u & C = 12u)

(a) 12 g of oxygen gas

(b) 20 g of water

(c) 22 g of carbon dioxide

(a) Atomic mass of Oxygen = 16 u

Molecular mass of Oxygen (O₂) = 16 x 2 = 32 g

Now, 1 mole of oxygen gas = Molecular mass of oxygen in grams = 32 g

Also, 32 g of Oxygen gas = 1 mole

   1 g of Oxygen gas = 1/32 mole                                                                                           

12 g of Oxygen gas = 1/32 X 12 = 0.375 mole

Hence, 12 g of Oxygen gas = 0.375 mole

(b) Molecular mass of water (H₂0) = 1 x 2 + 16 = 18u.

Now, 1 mole of water = Molecular mass of water in grams = 18 g

If 18 g of water = 1 mole

     1 g of water = 1/18 mole

Then , 20 g of water = 1/18 X 20 mole = 1.12 moles

Hence, 20 g of water = 1.12 moles

(c) Molecular mass of carbon dioxide (CO₂) = 12 + 16 x 2 = 12 + 32 = 44 u.

Now, 1 mole of carbon dioxide = Molecular mass of carbon dioxide in grams = 44g

If 44g of carbon dioxide = 1 mole

    1 g of carbon oxide = 1 /44 mole

Then, 22 g of carbon dioxide =22/44 = 0.5 mole

Hence, 22 g of carbon dioxide = 0.5 mole