Determine the pH of a KOH solution made by mixing .251g KOH with enough water to make 1.00x10^2 mL of solution

Question

A. 1.35
B. 2.35
C. 7.00
D. 11.65
E. 12.65

Answer 1

we calculate pOH = 1/[OH-] [OH-] = molarity of OH

10^2 mL = 0.1L
so a liter of your solution has a concentration of 2.51g
the molar mass of KOH is 39+16+1 =56
molarity of OH- = 2.51/56= 0.0448
pOH= log 1/0.0448=1.35
and you know pH+pOH= 14

so pH = 14-1.35=12.65

answer E