Home

Home
Common Compounds
Exam Guide
FAQ
Features
Glossary
Construction Kits
Companion Notes
Just Ask Antoine!
Simulations
Slide Index
Toolbox
Tutorial Index

FAQ
Introduction
Measurement
Matter
Atoms & ions
Compounds
Chemical change
The mole
Gases
Energy & change
The quantum theory
Electrons in atoms
The periodic table
Chemical bonds
Solids
Liquids
Solutions
Acids & bases
Redox reactions
Reaction rates
Organic chemistry
Everyday chemistry
Inorganic chemistry
Environmental chemistry
Laboratory
History of chemistry
Miscellaneous


Home :FAQ :The mole conceptPrint | Comment
Previous Question Next Question

How can I find the molecular weight of an organic acid?

My question is in regard to finding the molecular weight of an unknown organic acid. What would be the best way to go about doing it? I thought maybe by using a titration. Unfortunately, I am stuck at this point as what to do next.
christopher (jodiniz@zeus.kern.org)

A titration would work if you know how many ionizable hydrogens your organic acid has, and if you knew how pure the sample was. The following procedure could be used to get an estimate of the acid's molecular weight:
  1. Weigh the acid sample. If you know the purity, figure out how many grams of acid you actually have.
  2. Titrate the acid with a strong base solution of precisely known concentration (say, 0.1000 M KOH).
  3. Calculate how many moles of KOH were added.
  4. Convert moles of KOH to moles of acid.
  5. Divide the mass of acid you titrated by moles of acid and you have your molar mass.

That's probably the simplest way to do it. There are many other ways. For example, if the acid is volatile, you can try the Dumas method (The molecular weight is g/n which is approximately dRT/P, where d, P, and T are the experimentally measured density, pressure, and temperature of a vaporized acid sample at low pressure).

Author: Fred Senese senese@antoine.frostburg.edu



General Chemistry Online! How can I find the molecular weight of an organic acid?

Copyright © 1997-2010 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 08/17/15.URL: http://antoine.frostburg.edu/chem/senese/101/moles/faq/molecular-weight-by-titration.shtml