Question

35 g of sample of impure zinc reacts with 90.8 ml of hydrochloric acid which has specific
gravity 1.18 and contains 30% HCI by weight. What is the percentage purity of the zinc
metal ? Assume that the impurity does not react with HCI.
​

Answer 1

Answer:

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Answer 2

Answer:

2KClO

3

(s)→3O

2

(g)+2KCl

As 2 mol of KClO

3

gives 3 mol of O

2

. It means 245.2 g of KClO

3

gives 3 mol of O

2

.

So, 5.104 g ( 0.04 moles ) of KClO

3

will give ,

2

3

×0.04=0.06 moles of O

2

.

Now , Zn+2HCl→ZnCl

2

+H

2

.

65.4 g of Zn gives 1 mol of H

2

.

2H

2

+O

2

→2H

2

O

1 mol of O

2

reacts with 2 mol of H

2

.

So 0.06 mol of O

2

, produced by KClO

3

decomposition, will react with 0.12 mol of H

2

.

1 mol H

2

produced by 65.4 g of Zn, so 0.12 mol H

2

is produced by 65.4×0.12=7.85 g of Zn is required.