Deduce the number of molecules of the following compounds in the given quantities.

32g oxygen, 90g water, 8.8g carbon dioxide, 7.1g chlorine.

(a) 32g of oxygen

Moles = Mass of subtance in grams/Molecular mass

Molecular mass of oxygen = 16

Mass of a substance = 32g

Moles(n) = 32/16 = 2

n = 2 mol

2 mol of oxygen contains 6.022 x 10²³ molecules.

2 mol oxygen contains 2x6.022x10²³ molecules = 12.046 x 10²³ molecules.

(b) 90g water

Moles = Mass of subtance in grams/Molecular mass

Molecular mass of water = 18

Mass of a substance = 90g

Moles(n) = 90/18 = 5

n = 5 mol

5 mol of oxygen contains 6.022 x 10²³ molecules.

5 mol oxygen contains 5x6.022x10²³ molecules = 30.115× 10²³ molecules.

(c) 8.8g carbon dioxide

Moles = Mass of subtance in grams/Molecular mass

Molecular mass of CO₂ = 44

Mass of a substance = 8.8g

Moles(n) = 8.8/44 = 0.2

n = 0.2 mol

0.2 mol of oxygen contains 6.022 x 10²³ molecules.

0.2 mol oxygen contains 0.2x6.022x10²³ molecules = 1.2046 x 10²³ molecules.

(d) 7.1g chlorine.

Moles = Mass of subtance in grams/Molecular mass

Molecular mass of chlorine = 35.5

Mass of a substance = 7.1g

Moles(n) = 7.1/35.5 = 0.2

n = 0.2 mol

0.2 mol of oxygen contains 6.022 x 10²³ molecules.

0.2 mol oxygen contains 0.2x6.022x10²³ molecules = 1.2046 x 10²³ molecules.