Question

calculate volume of h2 gas kept at STP if it contains asany H atoms as in 98 gram H3PO4

Answer 1

Molar mass of the Phosphoric acid = 98 g/mole.

Mass of the Phosphoric acid = 98 g.

∴ No. of molecules of the Phosphoric acid = 6.022 × 10²³ molecules.

Now,

1 molecule of the Phosphoric acid have 3 atoms of Hydrogen.

∴ 6.022 × 10²³ molecules of Phosphoric acid have 6.022 × 10²³ × 3 atoms of Hydrogen = 1.81 × 10²⁴ atoms.

Now, Acc. to the question,

Hydrogen gas at S.T.P. also have the same number of atoms, i.e., 1.81 × 10²⁴ atoms.

∴ Mass of the Hydrogen containing 1.81 × 10²⁴ atoms. = Molar Mass × 1.81 × 10²⁴/Avogadro's number.

= 2 × 1.81 × 10²⁴/6.022 × 10²³

= 2 × 3

= 6 g.

We know that the 1 mole of any gas at S.T.P. occupies the volume of the 22.4 liter.

∴ 2 g of the Hydrogen at S.T.P. occupies the volume of the 22.4 liter.

∴ 6 g of the Hydrogen at S.T.P. occupies the volume of the 22.4 × 6/2 liter.

= 22.4 × 3 = 67.2 liter.

Hence, the volume of the Hydrogen at S.T.P. is 67.2 liter.

Hope it helps.