question_answer 1)

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 the pH of solution?

Answer:

\[M=\frac{{{w}_{B}}\times 1000}{{{m}_{B}}\times V}\] \[=\frac{0.56\times 1000}{56\times 200}=0.05M\] \[[{{K}^{+}}]=[O{{H}^{-}}]=0.05M\] \[[{{H}^{+}}]=\frac{{{K}^{w}}}{[O{{H}^{-}}]}\] \[=\frac{{{10}^{-14}}}{0.05}=2\times {{10}^{-13}}M\]