Hello Everyone, thanks for stopping by to read another post on a wonderful general chemistry topic called titrations.
Why you should understand titrations: Titrations are extremely useful in a lab setting. It's almost a rite of passage for a chemist to perform countless titrations during undergrad.
Key Ideas
- Titration Terms
- Titration Set up
- The Equivalence Point
- Titration Curves
Titration Terms
Before we get into titrations, there is some important terminology you should know. The titrant is the liquid that is in the burette with a known concentration. The titrand is the liquid in the flask below the burette with an unknown concentration. The equivalence point is the point during the titration where you've added the same amount of moles of titrant from the burette as the number of moles of titrand which are in the flask.
Titration Set up
A burette is a piece of glassware that can add very small amounts of volume with a low amount of error.
The stopcock is the nob that controls the amount of titrant released from the burette.
The Erlenmeyer Flask is the glassware that holds the analyte (or your solution of interest). Though it is not 100% necessary to use an Erlenmeyer flask, it's worth noting that it will prevent splattering when your titrant is added which can make your measurements more accurate.
The Equivalence Point
The equivalence point is the point during a titration where the moles of analyte and moles of titrant are equivalent. Typically, the equivalence point is measured by a color-changing indicator. When the color begins to change you know you've reached the equivalence point. However, indicators are a very qualitative way to measure the equivalence point. A pH meter can be used for more accurate quantification of the equivalence point. When using a pH meter, there will be a drastic change in the pH which signals that the equivalence point has been reached.
Titration Curves
In the example titration curve below, one axis quantifies the pH of the solution while the other quantifies the volume of titrant added. It's important to note that the pH being measured is the pH of the analyte solution as titrant is added.
Initially, the pH of our solution is very low. This means our titrand is acidic and our titrant is basic.
At the start of the titration, there is more acid in solution than base. As the acid and the base react, the pH becomes more basic.
When the pH changes drastically, we have reached the equivalence point. Where the pH of the solution is equal to the pKa and the moles of acid and base are the same.
If more base is added after we have reached the equivalence point, we will push the titration past the equivalence point. At this point, there is more base in solution which means the pH is higher than at the equivalence point.
I hope you've found this post on Titrations helpful. If you have any questions feel free to comment on this post, email me, or comment on the video I've linked below.
- Saren
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