Chapter 13 - The Chemistry of Solutes and Solutions - Questions for Review and Thought - Topical Questions - Page 605c: 58b

Mass fraction= 0.127 Weight percent= $12.7\%$

Mass fraction of ethanol= $\frac{mass\,of\, ethanol}{mass\,of\, ethanol+mass\,of\,water}=\frac{1.45\,g}{1.45\,g+10.0\,g}$ $=0.127$ Weight percent= mass fraction$\times100\%$ $=0.127\times100\%$ $=12.7\%$