Help with Biochemistry Homework: Formic Acid, pH & Buffer Solutions

  • Thread starter Thread starter stads_29
  • Start date Start date
  • Tags Tags
    Biochemistry
Click For Summary

Discussion Overview

The discussion revolves around a biochemistry homework problem involving formic acid, its pH, and buffer solutions. Participants are exploring the calculations related to the dissociation of formic acid, the ratio of conjugate base to weak acid, and the preparation of a buffer solution.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a homework question about calculating the pH of a solution containing formic acid and its conjugate base, specifying their concentrations.
  • Another participant suggests considering the equilibrium of formic acid dissociation to determine the concentration of hydrogen ions (H+).
  • A participant claims to have calculated the pH as 2.3 and questions the correctness of their result, while also expressing uncertainty about the ratio of conjugate base to weak acid.
  • There is a reference to the Henderson-Hasselbalch equation as a potential tool for solving the problem, with a suggestion to write it out for clarity.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the pH calculation or the ratio of conjugate base to weak acid. There is ongoing uncertainty and requests for clarification on the buffer preparation.

Contextual Notes

Participants have not provided detailed steps for their calculations, and there may be missing assumptions regarding the equilibrium state of the acid-base system. The discussion does not resolve the mathematical steps needed for the buffer preparation.

stads_29
Messages
3
Reaction score
0

Homework Statement


Hey, have this question which i just can't wrap my head around, any help would be appreciated.

Formic Acid (HCOOH) - pKa = 3.8 is a weak acid that partially dissociates to form its conjugate base (HCOO-) and releases protons into aqueous solutions. Whats the pH of a solution in which (HCOOH) = .7M and (HCOO-) = .15M?

Then, if the pH of sol. of Formic acid has been titrated to a final pH of 2.8, Whats the ratio of conjugate base : Weak acid?

And suppose your given stock solutions of formic acid and sodium salt of the conjugate base : (HCOOH) = 3.OM and (HCOONa) = 1.5M,
How would you make a .1 M buffer(total formic acid + sodium formate concentration), 100mL total at pH 3.5, using above solutions?

Homework Equations


The Attempt at a Solution

Hasselback equation
 
Physics news on Phys.org
stads_29 said:

Homework Statement


Hey, have this question which i just can't wrap my head around, any help would be appreciated.

Formic Acid (HCOOH) - pKa = 3.8 is a weak acid that partially dissociates to form its conjugate base (HCOO-) and releases protons into aqueous solutions. Whats the pH of a solution in which (HCOOH) = .7M and (HCOO-) = .15M?

Maybe this will start the neurons firing...

If you consider the equilibrium of formic acid to be

HCOOH <-----> H+ + HCOO-

and you know the concentration of HCOO-, how much H+ will you necessarily have?

Then, if the pH of sol. of Formic acid has been titrated to a final pH of 2.8, Whats the ratio of conjugate base : Weak acid?

And suppose your given stock solutions of formic acid and sodium salt of the conjugate base : (HCOOH) = 3.OM and (HCOONa) = 1.5M,
How would you make a .1 M buffer(total formic acid + sodium formate concentration), 100mL total at pH 3.5, using above solutions?


Homework Equations





The Attempt at a Solution

Hasselback equation

Yes, write out the Henderson Hasselbalch equation and see if you notice anything...

pH = pKa + Log([A-]/[HA])
 
ok got 2.3 as pH, is that right? Still not sure bout ratio. got 4.1 for the first part. Please help on the last part!? haven't clue what to do with buffer
 
2.3 - show how you get there.

--
methods
 

Similar threads

Chemistry How to take into account autoprotolysis in weak base solution?
  • · Replies 8 ·
Replies
8
Views
3K
Chemistry Are there typos in this snippet causing confusion?
  • · Replies 2 ·
Replies
2
Views
2K
Chemistry Understanding how to calculate pH of a buffer solution
  • · Replies 2 ·
Replies
2
Views
2K
Chemistry How to calculate pH at equivalence point using this alternative?
  • · Replies 7 ·
Replies
7
Views
2K
Chemistry Comparing methods of computing pH at equivalence point in titration
  • · Replies 4 ·
Replies
4
Views
2K
Chemistry Moles of NaOH to Create Buffer Solution pH=6 in 0.42M Ethanoic Acid
  • · Replies 3 ·
Replies
3
Views
3K
Find pH at Endpoint: Formic Acid Titration with NaOH Solution - 8.32 Answer
  • · Replies 2 ·
Replies
2
Views
5K
Calculating the pH of a Buffer Solution
  • · Replies 7 ·
Replies
7
Views
4K
How Do You Calculate the Molar Enthalpy of Formic Acid?
  • · Replies 3 ·
Replies
3
Views
6K
Which of the following combinations would act as buffered solutions
  • · Replies 5 ·
Replies
5
Views
5K