A 1.00 L buffer solution is 0.150 M in #HC_7H_5O_2# and 0.250 M in #LiC_7H_5O_2#. How do you calculate the pH of the solution after the addition of 100.0 mL of 1.00 M #HCl#? The Ka for #HC_7H_5O_2# is #6.5 × 10^–5#.
You can do it like this:
It looks like the acid is benzoic acid
For short - hand I'll call this
Benzoic acid dissociates:
The lithium salt provides a large reserve of the co - base
The initial no. moles of
You can see that they react in a 1:1 molar ratio so that the no. of moles of
Each mole of
The initial moles of
So the total moles
The expression for the acid dissociation constant
I will ignore any changes in concentration due to the dissociation of the acid as it is very small.
The total volume is common to both acid and co - base and will cancel so we can write: