im looking at some review problems my teacher gave me today, and i can pretty much do most of them. however, there is this one i really have no idea what to do. Its a 2 part problem.(adsbygoogle = window.adsbygoogle || []).push({});

1a.What is the pH of a 1000 ml of a 0.1 M acetic acid solution, given pKa = 4.8?

1b. what is the pH of 1000ml of 0.1 M acetic acid solution after you have added 5 ml of 10.0 M NaOH, assuming net volume change is negligible

so, for the first part, i think i got it wrong. But here is what i did.

First i found the Ka with

pKa = 4.8 = -log[Ka]

10^-4.8 = Ka

Ka = 1.58 x 10^5

so then i wrote out the equilibrium reaction.

C2H4O2 + H20 > C2H3O2 + H30

where everything is aqueous except H20, and the products on the right side are - and + ions, respectively.

so then

Ka = [x][x]/0.1 - x, where is x is the concentration of H30 and C2H3O2.

solving for x gives 1.25 * 10^-3

so, [Hplus] = 1.25 * 10^-3 M

then, i did this step

(1.25 x 10^-3 Hplus ions/L) * 1000ml * 1L/1000ml gives 1.25 x 10^-3 Hplus ions

pH = -log[Hplus] = 2.903

i really need help, im pretty sure i made some erroneous steps.

and for part b, i really didnt have any idea how to start. I just started by finding the number of mols of OHminus, but i dont think that does anything.

So, can someone help me do both parts?

thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# I have my acids and bases test tomorrow, and i need help with a few types of problems

**Physics Forums | Science Articles, Homework Help, Discussion**