Answer
The concentration of $KOH$ in that aqueous (water) solution is equal to 10.% (m/m).
Work Step by Step
1. Write the concentration expression:
$Concentration \space (m/m) = \frac{mass \space of \space solute \space }{mass \space of \space solution \space} \times 100 \%$
2. Substitute the values, and calculate the concentration:
$Concentration \space (m/m) = \frac{2.0 \space g }{20.0 \space g} \times 100 \% = 10. \%$
