# Homework Help: Titration concentration calculation problem, NaOH and HCl/HOAc mixture, help please

1. Oct 8, 2011

### Rissj3

Hi, I'm in lab in which we have to titrate 0.09M NaOH into 25mL of 0.1M HCl/HOAc mixture.

1. The problem statement, all variables and given/known data
I need help on how to calculate the concentration of HCl and HOAc in the mixture.

0.09M NaOH
1st equivalence point = 14.3mL
2nd equivalence point = 26.9mL

Difference of two equivalence points, 14.3-26.9= 12.6mL

2. Relevant equations
I'm thinking to solve this problem I would have to use the dilution formula, M1V1=M2V2

3. The attempt at a solution

M (0.025L) = (0.09M)(0.0143L)
M = 0.05148M HCl

M (0.025L) = (0.09M)(0.0126L)
M = 0.04536M HOAc

Is this correct or am I completely off?

Any help would be appreciated.

Thanks

2. Oct 9, 2011

### symbolipoint

Re: Titration concentration calculation problem, NaOH and HCl/HOAc mixture, help plea

To give a simplified explanation:
The weak acid will be picked at titrant addition to about pH of 4 to 4.5, and both the weak and strong acid will be neutralized at about pH 8 to 9. Your first equivalence point will give you moles of HOAc; your second equivalence point will give you moles of both HOAc and HCl combined. The difference will be for the moles of HCl alone.

3. Oct 9, 2011

### Staff: Mentor

Re: Titration concentration calculation problem, NaOH and HCl/HOAc mixture, help plea

Since when titration is identical to dilution?

http://www.titrations.info/titration-calculation

Formula you listed happens to be identical to the one needed in SOME cases. The longer you will believe it works always, the worse for you.