Chemistry) Buffers and Ph differences question

[Stevo11]

Homework Statement

A Chemist wishes to prepare 250mL of buffer that has a Ph of 4.50. Starting with 100mL of 0.12 mol L acetic acid and a supply of 0.10 mol L NaOh.
1) explain how this can be done
3) how much 0.20 molL NaOH must e added to this buffer to raise the pH to 5.1?
3) if the same amount of 0.20 mol L NaOH were added to 250mL of Dionized water, what would the new pH be?

Homework Equations

I know the henderson equation has to be used somewhere but I'm honestly stumped at where to even start any general push in the right direction would be seriously appreciated, It's a bonus Lab question, but I'd still like to get any extra marks I could :)

 

[Borek]

When you add NaOH to the solution of acetic acid, you neutralize it, producing sodium acetate. Just add enough to get a correct ratio given by the HH equation.