What is the pH if 10 mL of a 10 M solution of NaOH is added

What is the pH if 1.0 mL of a 1.0 M solution of NaOH is added to 5 mL of 0.9 Acetic Acid?

I need to know the simple step by step formula to do this. I have to do the equation starting if 1.0 mL of NaOH is added, if 2.0 mL is added, ... all the way to 20.0 mL. Thanks!

Solution

M1 = 1M (NaOH)

V1 = 1ml

M2 = 0.9M (acetic acid)

V2 = 5ml

now OH- concentration = M1*V1-M2*V2/(V1+V2)

--------for 1ml NaOH = 1*1-0.9*5/(1+5) = -0.58

--------for 2ml NaOH = 1*2-0.9*5(2+5)= -0.357

--------for 20 ml NaOH = 1*20-0.9*5(20+5) = 0.62

pH = 14+log10[OH-] = 13.79