Question

A certain metal sulphide, M\(_2\)S\(_2\), is used extensively as a high temperature lubricant. If M\(_2\)S\(_2\) is 40.06 % by mass sulphur, the atomic mass of metal M is:

• A. 160 u
• B. 64 u
• C. 40 u
• D. 96 u

Hint:

In % composition problems, use the given mass % of an element to form an equation involving the molar masses of the compound and its elements. This will help determine the atomic mass of the unknown element.

Answer 1

The Correct Option is D

\[ MS - 2 = M + 32 \times 2 = M + 64 \] \[ \% { of sulphur} = \left( \frac{64}{M + 64} \right) \times 100 = 40.06 \] \[ M + 64 = \frac{6400}{40.06} \] \[ M + 64 = 160 \] \[ M = 160 - 64 = 96u \]