Final answer:
To produce a 0.5% solution, 0.86 ml of water must be added to 12.5 ml of the 6% stock solution.
Step-by-step explanation:
To calculate the volume of water that must be added, we can use the formula:
(% of stock solution)(Volume of stock solution) = (% of desired solution)(Total volume of the solution)
Plugging in the given values:
(6%)(12.5 ml) = (0.5%)(Volume of stock solution + 12.5 ml)
Solving for the volume of stock solution:
0.075 ml = 0.005(Volume of stock solution + 12.5 ml)
Volume of stock solution = 0.075 ml / 0.005 - 12.5 ml
Volume of stock solution = 0.86 ml