[oja]

(a) What is the pH of a 2.0 molar solution of acetic acid. Ka of acetic acid = 1.8 x 10¯5

(b) A buffer solution is prepared by adding 0.10 liter of 2.0 molar acetic acid solution to 0.1 liter of a 1.0 molar sodium hydroxide solution. Compute the hydrogen ion concentration of the buffer solution.

(c) Suppose that 0.10 liter of 0.50 molar hydrochloric acid is added to 0.040 liter of the buffer prepared in (b). Compute the hydrogen ion concentration of the resulting solution.

I am just wondering if my answers for the first two parts are correct
For a) pH 2.22
b) H+ concentration is 1.8 x 10^-5
and how could you start part C do you find the moles of HCL and what do you do with .04 liter?

Thank you in advance

[Borek]

a & b OK, as for C - H⁺ from HCl protonates CH₃COO^-. It is either buffer question or limiting reagent question

[oja]

So for the equation HC2H3O2 <---> H+  +   C2H3O2-

You are adding HCL -->  H+   +   Cl- 

So the H+ ions added to the first equation will make the reaction go left so you subtract on the right side and add on the left side.  What the starting concentration for C2H3O2 and HC2H3O2?  Thats my problem I do not know how to get that?

The Molarity for HCL is .357 right?  How could you recalculate the concentrations part b for part c?

[Borek]

If you know what is the pH in B you should be able to calculate HA and A^- concentrations. You may safely assume that neutralization in B went to completion and that protonation in C goes to completion as well.

Do all your calculations using just numbers of moles of substances, use total volume at the end to calculate concentrations.

[oja]

Could you please start me off because I have no idea what I am doing for part c

Thank you

[Borek]

Start with B solution - write down what ions and at what concentrations does it contain.

[oja]

For the last part C) I got .214 concentration for H+

Is that correct?

Thank you

[Borek]

Show your calculations.

[oja]

HCL--> H+   +   Cl-

HC2H3O2 <-> H+    +   C2H3O2-

for H + concentration in the HCL equation is .357 M because .1x.5/.14

for second equation got .143M for HC2H3O2 and C2H3O2  .5x.1/.14

add the HCL in which means all the C2H3O2 will be used up and H+ ions will be left.

So .357-.143= .214M for H+

Is it right?
Thanks

[Borek]

Looks OK. But I am known to be occasionally wrong