Chapter 4 Stoichiometry: Quantitative Information about Chemical Reactions - Study Questions - Page 179k: 131

$3.31$

Mass of $CaCl_2$ dissolved: $74.5\ g/100\ g\times 80\ g=59.6\ g$, Number of moles of $CaCl_2$ dissolved: $59.6\ g\div 110.98\ g/mol=0.537\ mol$ Remaining water: $150\ g-74.9\ g-59.6\ g=15.5\ g$ Number of moles of remaining water: $15.5\ g\div 18.015\ g/mol=0.860\ mol$ Number of moles of the hydrated salt: $74.9\ g\div219.07\ g/mol=0.342\ mol$ Ratio: $(0.342\times6+0.860)/(0.342+0.537)=3.31$