Question

A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure.
(a) Find the number of moles of hydrogen present
(b) What weight of CO₂can the cylinder hold under similar conditions of temperature and pressure? (H = 1 C = 12, O = 16)
(c) If the number of molecules of hydrogen in the cylinder is X, calculate the number of CO₂ molecules in the cylinder with the same conditions of temperature and pressure.
(d) State the law that helped you to arrive at the above result.

Answer 1

(a) Given:
Mass of hydrogen = 1kg at 298K and 1 at m pressure
Moles of hydrogen = ?
Number of moles of hydrogen = `"Mass of hydrogen"/"Gram atomic mass of hydrogen"`

= `[1000 "g"]/[1 "g"]`

= 1000 moles of hydrogen
(b) Molecular mass of CO₂ = 12 + 2 x 16 = 44g
So, 
vapour density (VD) = `"mol. Mass"/2` = `44/2` = 22

V.D. = `"mass of certain amount of CO"_2/"mass of equal volume of hydrogen"` = `"m"/1`

22 = `"m"/1`

So, mass of CO₂ = 22 Kg

(c) According to Avogadro's law, equal volumes of all gases under similar conditions of temperature and pressure contain equal number of molecules.

(d) So, number of molecules of carbon dioxide in the cylinder = number of molecules of hydrogen in the cylinder = X