Question

4.5 g of aluminium is deposited at cathode from Al3+ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from H+ ions in solution by the same quantity of electric discharge will be

Answer 1

The mole ratio of Aluminium to Hydrogen ions is :

3 : 1

The Molar mass of Aluminium is 27 g

We can now get the moles of Aluminium.

Moles of Aluminium is given by :

Moles = Mass / molar mass

= 4.5/27 = 0.1667 moles

Given that the mole ratio is 3:1 the moles of hydrogen will be :

0.1667/3 = 0.05556 moles

Molar gas volume at stp is :

1 Mole = 22400 cm³

The volume of hydrogen evolved will be :

22400 × 0.05556 moles = 1244.544 cm³

Answer 2

Eq.wt.of Al =27/3=9

No.of eq.of Al=4.5/9=0.5

No.of faraday required =0.5

No of eq. Of H2 produce=0.5 eq. Volume occupied by 1 eq. Of H2=22.4/2=11.2

Volume occupied by 0.5 =11.2×0.5=5.6 at STP