Answer
There are necessary 9.0 g of $KOH$ to prepare 450 mL of that solution.
Work Step by Step
1. Identify the conversion factors:
- Since the $KOH$ solution is 2.0% (m/v):
2.0 g (Solute) = 100 mL (Solution)
So: $\frac{2.0 \space g \space (Solute)}{100 \space mL \space (Solution)}$ and $\frac{100 \space mL \space (Solution)}{2.0 \space g \space (Solute)}$
2. Calculate the mass of solute needed to prepare 450 mL of that solution:
$450 \space mL \space (Solution) \times \frac{2.0 \space g \space (Solute)}{100 \space mL \space (Solution)} = 9.0 \space g \space (Solute)$