Numero di moli= MxV
moli KOH 0,5M = (5x10-1) x (5x10-2 ) =250x10-4
moli KOH 5x10-2M= (5x10-2) x (5x10-2) =25x10-4

Moli tot.=275x10-4

M= moli / Volume
M = 275x10-4/1x10-1=275x10-3

pOH= - log 275x10-3= -log275-log10-3= -2.44+3 = 0.56
pH= 14 - 0.56 = 13.44