If the mole fraction of Na2S in an aqueous solution is 0.125,
what is the weight/weight %
(percent by mass) of Na2S?

Explanation:

Hello,

In this case the molar fraction of sodium sulfide, whose molar mass is 78 g/mol, is 0.125, it means we have 0.125 moles of sodium sulfide per mole of solution, so we compute the mass of sodium sulfide and water as shown below:

Then, we can calculate the eight/weight % as follows:

Regards.

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