Solve 5pH Solution from Citric Acid (1L)

  • Thread starter Thread starter vande060
  • Start date Start date
  • Tags Tags
    Chemistry Ph
Click For Summary
SUMMARY

To prepare a 5 pH solution from citric acid, one must consider the triprotic nature of citric acid, which has pKa values of 3.13, 4.76, and 6.40. The calculation of [H+] involves using the antilog function, resulting in a required concentration of 10^-5 M H+. However, due to the weak acid characteristics of citric acid, the initial concentration calculated is insufficient, necessitating adjustments through trial and error. The discussion suggests that the problem may also pertain to creating a citric buffer rather than solely preparing a citric acid solution.

PREREQUISITES
  • Understanding of pH and its calculation using the formula pH = log(H+)
  • Knowledge of triprotic acids and their dissociation constants (pKa)
  • Familiarity with molarity and mole calculations
  • Experience with acid-base titration concepts
NEXT STEPS
  • Research the preparation of buffer solutions, specifically citric acid buffers
  • Learn about the Henderson-Hasselbalch equation for pH calculations
  • Explore software tools for acid-base equilibrium calculations
  • Study the properties and applications of weak acids in solution chemistry
USEFUL FOR

Chemistry students, laboratory technicians, and anyone involved in solution preparation and acid-base chemistry will benefit from this discussion.

vande060
Messages
180
Reaction score
0

Homework Statement



how would you make a 5pH solution from citric acid(1L)



Homework Equations



pH= log(H+)


The Attempt at a Solution



So I will try to work backwards from the [H+]

antilog(-5) = 10^-5 M H+ needed

this number can be divided by 3, because citric acid is triprotic

3.33*10^-6 moles * 210.14 g/mol = 7*10^-4 g brought to volume with 1 liter
 
Physics news on Phys.org
That would be way too simple. Citric acid is a weak one, with pKa values of 3.13, 4.76 and 6.40, so at pH 5.0 none of the protons is dissociated 100%. That means your assumption is faulty, and concentration you calculated - while not far from the correct answer - is too low.

To be honest, I can't think of a simple and accurate approach to solving the question on paper. It is not a problem using - although it requires some trial and error to get the correct concentration, as program calculates pH for a given concentration, but it doesn't work the other way around.

Are you sure the problem is about using citric acid and not about preparing citric buffer?
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
3K
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 5 ·
Replies
5
Views
8K