We are required to calculate the molarity, given:
Volume = 150 mL = 0.150 L
mass of KOH = 25.0 g
Formular for molarity:
C = n/V
Before we can get C, we need to calculate n, the number of moles of KOH.
n = m/M where m is the mass and M is the molar mass
n = 25.0 g/56,1056 g/mol
n = 0.446 mol
Now we can calculate C, the molarity
C = 0.446 mol/0.150L
C = 2.97 mol/L or 2.97 M