How is weak acid concentration measured?

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SUMMARY

The concentration of a weak acid, such as acetic acid (CH3COOH), is defined as the total molarity of the acid in solution, which includes both dissociated and undissociated forms. In the case of a 0.100M CH3COOH solution, this value represents the total concentration of acetic acid present, irrespective of its dissociation into CH3COO- and H+. Therefore, when measuring weak acid concentration, one refers to the total molarity rather than the equilibrium concentration alone.

PREREQUISITES
  • Understanding of weak acid dissociation and equilibrium concepts.
  • Familiarity with molarity and concentration calculations.
  • Basic knowledge of chemical equations and reactions.
  • Awareness of the properties of acetic acid (CH3COOH).
NEXT STEPS
  • Research the concept of acid dissociation constants (Ka) for weak acids.
  • Learn about the Henderson-Hasselbalch equation for buffer solutions.
  • Investigate the effects of temperature on weak acid dissociation.
  • Explore titration methods for determining weak acid concentrations.
USEFUL FOR

Chemistry students, laboratory technicians, and anyone involved in chemical analysis or studying acid-base equilibria will benefit from this discussion.

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Is a weak acids concentration determined from when it is in equilibrium, or if it hasn't dissociated at all?
i.e. 0.100M CH3COOH. Would this be the concentration of CH3COOH during it's equilibrium:
CH3COOH <-|-> CH3COO- + H+
Or just by itself?

Thanks!
 
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0.100M is usually total concentration of acid - both dissociated and not dissociated.
 
Yeah the molarity of a weak acid solution is a measure of the amount of the acid in there, regardless of whether its dissociated or not. So if I add 0.1 moles of acetic acid to a litre of water, I get a 0.1M acetic acid solution.
 

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