what is the pOH of solution?

Question

0.003 mol NaOH and 0.003 mol Ba(OH)2 are completly dissolved in water to make1L of solution at 25C, what is the pOH of solution?

thanks guys.. if u can help me out

Answer 1

First find how many moles of OH- are produced by NaOH

NaOH -> Na+ +OH-
1 mole NaOH gives 1 mole OH-
0.003 mole give x
x=0.003

Then find how many moles of OH- are produced from Ba(OH)2
Ba(OH)2 -> Ba(+2) +2OH-
1 mole Ba(OH)2 gives 2 mole OH-
0.003 mole give x
Thus x=2*0.003= 0.006

Find the total number of OH- mole = 0.003+0.006= 0.009
Divide by the volume expressed in L to find the concentration:
[OH-]= 0.009/1 =0.009 mole/L

so pOH = -log[OH] =-log(0.009) = 2.05