Question

How many ml of 20% solution and how many ml of sterile water are needed to prepare 500 ml of 2% solution?

Answer 1

Available concentration (stock) = 20% = 20/100

Required = 500 mL of 2% concentration

Formula

Volume of stock required = (required concentration/stock concentration) *required volume = (2%/20%)*500 = {(2/100)/(20/100)} *500= 50 mL

Volume of water required = required volume - required stock volume = 500 - 50 = 450 mL

Therfore 50 mL of 20% stock solution and 450 mL of sterile water is required to prepare 500 mL of 2% solution.

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