Isotonic saline typically has a concentration of 0.9% sodium chloride (NaCl). To find the grams of solute in 73.0 mL of isotonic saline, you can use the formula: grams of solute = volume (mL) × concentration (g/mL). Since 0.9% saline means 0.9 grams of NaCl per 100 mL, for 73.0 mL, the calculation is (73.0 mL × 0.009 g/mL) = 0.657 grams of NaCl.