The answer is 49 mL of water. Looking at the chart for solubility measured in grams of solute per 100 mL of water solvent, 105 grams of sodium nitrate NaNO3 will dissolve in 100 mL water at 40 degrees Celsius. Using this value for the solubility of NaNO3, we now calculate for the amount of water that will dissolve 51 grams of NaNO3: mL H2O = 51g of NaNO3 * 100mL H2O/105g NaNO3
= 48.57 mL ≈ 49 mL
