How Do You Calculate pH After Titration of HOBr with NaOH?

[gerry73191]

Homework Statement

20.0 mL of a 0.1 M solution of sodium hydroxide is titrated into 50.0 ml of the 0.14 M HOBr solution. Calculate the pH of the resulting solution.

ph of HOBr is 4.74

Ka is 2.3e-9

Homework Equations

[H+] = ka(a/b)

-log[h+] = ph

ka*kb=kw

The Attempt at a Solution

honestly i have no clue how to do this problem. I already know the answer its 8.24, but I haven't a clue how to get it. can someone point me in the right direction?

thanks

 

[Borek]

Calculate concentrations of HOBr and OBr^- (just from the neutralization reaction stoichiometry), plug these numbers in the Henderson-Hasselbalch equation.

 

[Blueshift5]

Based on the given information, it seems like this is a buffer problem involving a weak acid (HOBr) and its conjugate base (OBr-). The first step would be to calculate the initial concentrations of both the acid and base in the solution. Since we know the volume and molarity of each solution, we can use the formula M1V1 = M2V2 to find the number of moles of each substance present.

For HOBr:

M1 = 0.14 M

V1 = 50.0 mL = 0.050 L

M2 = unknown (let's call it x M)

V2 = 50.0 mL = 0.050 L

Using the formula, we get:

(0.14 M)(0.050 L) = (x M)(0.050 L)

x = 0.14 M

So the initial concentration of HOBr in the solution is 0.14 M.

For OBr-:

M1 = 0.1 M

V1 = 20.0 mL = 0.020 L

M2 = unknown (let's call it y M)

V2 = 50.0 mL = 0.050 L

Using the formula, we get:

(0.1 M)(0.020 L) = (y M)(0.050 L)

y = 0.04 M

So the initial concentration of OBr- in the solution is 0.04 M.

Next, we can use the Henderson-Hasselbalch equation to calculate the pH of the resulting solution:

pH = pKa + log([base]/[acid])

pH = 4.74 + log(0.04/0.14)

pH = 4.74 + log(0.2857)

pH = 4.74 + (-0.544)

pH = 4.196

However, this is not the final answer because the titration of a weak acid with a strong base creates a buffer solution, and the pH of a buffer solution is affected by the ratio of the concentrations of the acid and base. In this case, the initial concentrations of HOBr and OBr- are not equal, so we need to use the Henderson-Hasselbalch equation again, but this time with the final concentrations of the acid and base.

To calculate the final concentrations, we need to use the neutral