7.57 If 0.561 g of KOH is dissolved in water to give 200 mL of solution at 298 K. Calculate the concentrations of potassium, hydrogen and hydroxyl ions. What is its pH?

[KOHaq]=0.56115g/L
=2.805g/L
=2.805×156.11M
=.05 M
KOH(aq)K(aq)++OH-(aq)
[OH-]=.05 M =[K+]
[H+][H-]=Kw
[H+]=Kw[OH-]
=10-140.05=2×10-13M
pH=12.70