The pOH of a solution : 13.756
Mass HCl=10.4 g
mol HCl (MW=36.5 g/mol) :
[tex]\tt mol=\dfrac{mass}{MW}=\dfrac{10.4}{36.5}=0.285[/tex]
Volume of HCl = 500 ml = 0.5 L
[tex]\tt M=\dfrac{n}{V}\\\\M=\dfrac{0.285}{0.5}=0.57~M[/tex]
HCl ⇒ H⁺ + Cl⁻
[H⁺]=[HCl]=0.57 M
pH= - log[H⁺]
pH=-log[0.57]=0.244
pH+pOH=14
pOH=14-0.244
pOH=13.756