Question

When ZnS is strongly heated in excess of air, zinc oxide is formed & gases SO2 is reduced. Calculatemthe mass of ZnO & SO2 can be obtained from 4.866g of ZnS?

Answer 1

Explanation:

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Answer 2

Answer:

Start by taking a look at the balanced chemical equation that describes this reaction. Zinc sulfide will react with oxygen gas to produce zinc oxide and sulfur dioxide.

2

ZnS

(

s

)

+

3

O

2

(

g

)

→

2

ZnO

(

s

)

+

2

SO

2

(

g

)

Now, you know that your sample of zinc sulfide undergoes partial oxidation, which means that only a fraction of the mass of zinc sulfide will react to produce zinc oxide.

Notice that zinc sulfide and zinc oxide are present in a

1

:

1

mole ratio because it takes

2

moles of zinc sulfide to produce

2

moles of zinc oxide.

Use the molar masses of the two compounds to convert this mole ratio to a gram ratio.

You will have

1 mole ZnS

1 mole ZnO

=

1

mole ZnS

⋅

97.474 g

1

mole ZnS

1

mole ZnO

⋅

81.40 g

1

mole ZnO

=

97.474 g ZnS

81.40 g ZnO

So, you know that the reaction produces

81.40 g

of zinc oxide for every

97.474 g

of zinc sulfide that take part in the reaction.

This is equivalent to saying that when

1 g

of zinc sulfide is oxidized, the reaction produces

0.8351 g

of zinc oxide.

In other words, if the reaction consumes

1 g

of zinc sulfide, the total mass of the sample will decrease by

ZnS consumed



1 g

−

ZnO produced



0.8351 g

=

0.1649 g

In your case, the total mass of the sample decreases by

50 g

−

44 g

=

6 g

which means that the reaction must have consumed

6

g decrease

⋅

1 g ZnS

0.1649

g decrease

=

36.39 g

This implies that the resultant mixture contains

what you start with



50 g ZnS

−

what is consumed



36.39 g ZnS

=

what remains unconsumed



13.6 g ZnS

Consequently, the resultant mixture also contains

ZnS + ZnO



44 g

−

ZnS



13.6 g

=

ZnO



30.4 g

Therefore, you can say that the resulting mixture contains zinc oxide and zinc sulfide in a

30.4

:

13.6

gram ratio, which is pretty close to option (D).

The difference between the values was probably caused by the values I used for the molar masses of the two compounds.