Answer:
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:
[tex]m_{Na_2S}=0.125mol*\frac{78gNa_2S}{1molNa_2S} =9.75 gNa_2S\\\\m_{H_2O}=(1-0.125)molH_2O*\frac{18gH_2O}{1molH_2O} =15.75gH_2O[/tex]
Then, we can calculate the eight/weight % as follows:
[tex]w/w \%=\frac{9.75g}{9.75g+15.75g}*100\% \\\\w/w \%=38\%[/tex]
Regards.
