- #1

Hammad Shahid

- 64

- 3

- TL;DR Summary
- Can I do this?

HCH3COO + H2O <<-> H3O+ + CH3COO- ; K= 1.8*10^-5

H3O+ + OH- <->>>>> 2H2O ; K= 10^14

Net Equation:

HCH3COO + OH- <->>> H2O + CH3COO-

K= (1.8*10^-5) * (10^14) = 1.8*10^9 = extremely large

The problem states that I'm adding a certain volume of a known [KOH] to a certain volume of a known [HCH3COO].

The goal is to calculate the final pH.

Since I don't know the K value of the rxn of HA w/ OH-, I set up 2 equations and combined their K values to derive the K value.

Since the new K value is extremely large, I assume the reaction goes fully to completely and that all OH- (limiting reagent) reacts with the HCH3COO to provide an equivalent amount of conjugate base and an excess HCH3COO.

Next, since I find the concentrations of the acid and the conjugate base. Since they are of appreciable amounts, I can assume that the initial volumes of both change negligibly.

Finally, I use the Henderson-Hasselbach equation to find the pH.*My question is: is this a legit way to solve this problem?

Thank you.

The goal is to calculate the final pH.

Since I don't know the K value of the rxn of HA w/ OH-, I set up 2 equations and combined their K values to derive the K value.

Since the new K value is extremely large, I assume the reaction goes fully to completely and that all OH- (limiting reagent) reacts with the HCH3COO to provide an equivalent amount of conjugate base and an excess HCH3COO.

Next, since I find the concentrations of the acid and the conjugate base. Since they are of appreciable amounts, I can assume that the initial volumes of both change negligibly.

Finally, I use the Henderson-Hasselbach equation to find the pH.*My question is: is this a legit way to solve this problem?

Thank you.