Question

Impure sample of ZnS contains 42.34% Zn. What is the percentage of pure ZnS in the sample? (a) 67% (b) 63% (C) 58% (d) 37% ​

Answer 1

Explanation:

70% is approximately equal to the 67%

therefore answer is (a) 67%

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Answer 2

Given - Impure sample of ZnS contains 42.34% Zn

Find - Percentage of pure ZnS in the sample

Solution - Molecular mass of Zinc sulphate = 97 gram/mol

Mass of Zinc = 65 gram

Percentage of Zinc in pure sample = 65/97

Percentage of Zinc in pure sample = 67%

Hence, percentage of Sulphur in pure sample of ZnS = 100 - 67%

Percentage of Sulphur = 33%

Percentage of Zinc in impure ZnS = 42.34%

As per Law of Constant Composition, finding out percentage of Sulphate in the sample.

%Zn/%S (pure) = %Zn/%S (impure)

67/33 = 42.34/%S

%S = 42.34*33/67

%S = 20.85%

So, percentage of pure ZnS = 42.34 + 20.85

Percentage of pure ZnS = 63%

Thus, correct answer is (b) 63%.