calculate the pH of the 120mL of a 0.12 M HCOONa,Ka=1.8*10^-5,solution are added to 50mL of a 0.05 M H2SO4 solution.Determine the pH of the sodium formate solution before and after the H2SO4 addition.

please someone help me!

I ASSUME this is a beginning class and they expect you to view H2SO4 as a dibasic acid; i.e., 0.05M x 2 = 0.1M in (H^+). Actually, that isn't right as (H^+) really is closer to o.059M and not 0.1. But we will go with the assumption. Let's call formic acid as HFm to save typing and formate as Fm^-

millimols Fm^- = mL x M = 120 x 0.12 = 14.4
mmols H2SO4 = 50 x 0.1 M = 5.0
.......Fm^- + H^+ ==> HFm
I.....14.4....0........0
Add..........5.0.......0
C.....-5.0..-5.0.......5.0
E.....9.4.....0........5.0
Plug the E line into the Henderson-Hasselbalch equation and solve for pH.

For part A, the pH of the formate by itself, that's a hydrolysis question.
.......Fm^- + HOH ==> HFm + OH^-
I....0.12..............0....0
C.....-x...............x....x
E..0.12-x..............x....x

Kb for Fm^- = (Kw/Ka for HFm) = (x)(x)/0.12-x
Solve for x = (O)H^-) and convert to pH.

To determine the pH of the sodium formate (HCOONa) solution before and after the addition of H2SO4, we need to consider the dissociation reactions of both compounds.

Before adding H2SO4:
HCOONa dissociates as follows:
HCOONa → HCOO- + Na+
The concentration of the sodium formate in the solution is given as 0.12 M.

H2SO4 dissociates in two stages, with the first stage being more significant:
H2SO4 → H+ + HSO4-
HSO4- ⇌ H+ + SO4^2-
The concentration of H2SO4 in the solution is given as 0.05 M.

We can observe that the HCOONa solution is a salt of a weak acid (HCOOH) and a weak base (NaOH). In the presence of water, it will undergo hydrolysis to produce HCOOH and NaOH. However, since the concentration of HCOONa is significantly larger than that of H2SO4, the effect of hydrolysis from HCOONa can be neglected.

Now, let's move forward to determine the pH before adding H2SO4:

Step 1: Calculate the initial concentration of HCOO- (formed from HCOONa dissociation).
Since HCOONa completely dissociates into its constituent ions, the initial concentration of HCOO- is also 0.12 M.

Step 2: Calculate the initial concentration of H+.
Since no acid has been added yet, there are no additional H+ ions present in the solution. The concentration of H+ is initially zero.

Step 3: Calculate the pH.
The pH of a solution can be calculated using the equation:
pH = -log [H+]
However, since the concentration of H+ is zero at this stage, the pH is undefined.

After adding H2SO4, the following reactions occur:

1. The H2SO4 fully dissociates, contributing H+ ions to the solution:
H2SO4 → 2H+ + SO4^2-.

2. The HCOO- reacts with the H+ ions from the H2SO4:
HCOO- + H+ ⇌ HCOOH.
This is an equilibrium that results in the formation of the weak acid, formic acid (HCOOH).

The pH after adding H2SO4 will depend on the stoichiometry of the reaction between HCOO- and H+.

Unfortunately, without providing the exact concentrations of HCOO- and the equilibrium constant (Ka) for the reaction between HCOO- and H+, it is not possible to calculate the exact pH of the solution after the addition of H2SO4.

To solve the problem, you need to provide the missing information (concentration of HCOO- and Ka) or clarify if any additional information is available to proceed with the calculations.