Question

Calculate volume of H2  gas kept at STP. if it is  contains as many H atoms as in 98gm of H3PO4 (Atomic mass of P =31)
A) 68.1 L
B) 33.6 L
C) 34.05 L
D) 44 L​

Answer 1

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Answer 2

Answer:

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...