PH of buffer solution

[pari786]

Homework Statement

Calculate the final pH of the following solutions:
a) 65.0 ml of 0.105 M HCl and 100 ml of 0.118 M sodium acetate solutions are mixed.
b) 100 ml of a 0.109 M acetic acid and 100 ml of a 0.123 ml NaOH solution are mixed.

Homework Equations

pH = pKa = log (salt/acid)

The Attempt at a Solution

for part a) i found the no.of moles of salt sodium aceate

0.118 mol/L x 0.1 L = 0.0118 mol

then after that I don't know how to fing the concentration of acid ... and if I know I can do the rest of the part a) using stoichiometric caluclations ... please help me with it

for part b) the same problem

I need immediate help beause this is due in 5 hours ... please do something about it
Thanks in advance

 

[linuxux]

here, http://chimge.unil.ch/En/ph/1ph57.htm [Broken] --->HCL and Acetate

and here, http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/equivalence-point-HOAc-NaOH.shtml--->NaOH and Acetate ---> this ones is for equivalence point, but you should be able to adapt it.

 

[Borek]

1. Just assume acetate is stoichiometrically protonated by the strong acid.

2. There is an excess of base - so there is no buffer solution. Once again, assume reaction (neutralization) was stoichiometric. pH is determined by the excess base alone.