Massachusetts Pharmacy Technician License Practice Test

How many mL of D10W are needed to prepare 500 mL of D7.5W with the given formula?

1. 25 mL

2. 37 mL

3. 50 mL

4. 75 mL

The correct answer is: 37 mL

To determine how many milliliters of D10W (a 10% dextrose solution) are needed to prepare 500 mL of D7.5W (a 7.5% dextrose solution), we can use the concept of dilution and the formula for mixing solutions: C1V1 + C2V2 = C3V3 Where: - C1 is the concentration of the first solution (D10W, 10%). - V1 is the volume of the first solution that we need to find (the volume of D10W). - C2 is the concentration of the second solution (which we can assume to be 0% for the solvent since we are mixing with water). - V2 is the volume of the second solution (the volume of water, which is part of the remaining volume to reach 500 mL). - C3 is the concentration of the mixture (D7.5W, 7.5%). - V3 is the total volume of the mixture (500 mL). Rearranging this equation to find V1 gives us: V1 = (C3V3 - C2V2) / C1 Assuming that