Question

A gas cylinder contains 12 x 10²⁴ molecules of oxygen gas.

If Avogadro’s number is 6 x 10²³; Calculate:

1)The mass of oxygen present in the cylinder.

2) The volume of oxygen at S.T.P. present in the cylinder. [O = 16]

Answer 1

1) 1 mole oxygen molecule = 6.022 x 10²³ molecules

x moles of oxygen molecule = 12 x 10²⁴ molecules

19.93 moles of oxygen molecule = 12 x 10²⁴ molecules.

Number moles of O₂ = `("Mass of" O_2)/("Molar mass of " O_2)`

Mass of O₂ = 32 x 19.93 = 637.76 g

2) 6.022 x 10²³ molceules occupies 22.4 L

12 x 10²⁴ molecules occupies = `(12 xx 10^24 xx22.4)/(6.022 xx 10^23)` = 446.36 L volume