Answer: To prepare a 3.0% (m/v) solution of KOH, we need to dilute the 18.0% solution by adding water. We can use the formula:
C1V1 = C2V2
where C1 and V1 are the initial concentration and volume of the concentrated solution, and C2 and V2 are the final concentration and volume of the diluted solution.
We want to prepare a 3.0% solution, which means that we need 3.0 g of KOH per 100 mL of solution. Therefore, if we want to prepare 100 mL of the 3.0% solution, we need to use the formula:
C1V1 = C2V2
(0.18)(V1) = (0.03)(100 mL)
V1 = (0.03/0.18)(100 mL)
V1 = 16.67 mL
So, we need to take 16.67 mL of the 18.0% solution and dilute it with water to a final volume of 100 mL to prepare a 3.0% (m/v) solution of KOH.
To find out the amount of water needed, we can subtract the volume of the concentrated solution from the final volume of the diluted solution:
Water volume = 100 mL - 16.67 mL = 83.33 mL
Therefore, to prepare a 100 mL of 3.0% (m/v) solution of KOH, we need to take 16.67 mL of the 18.0% solution and add 83.33 mL of water.
Step-by-step explanation: