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Acids and Bases - Titration Curves


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Strong Acid Titration Curve
Strong Acid Titration Curve

Strong Acid Titration Curve

Todd Helmenstine
Titration is a technique used in analytical chemistry to determine the concentration of an unknown acid or base. Titration involves the slow addition of one solution where the concentration is known to a known volume of another solution where the concentration is unknown until the reaction reaches a desired level. For acid/base titrations, a color change from a pH indicator is reached or a direct reading using a pH meter. This information can be used to calculate the concentration of the unknown solution.

If the pH of an acid solution is plotted against the amount of base added during a titration, the shape of the graph is called a titration curve. All acid titration curves follow the same basic shapes.

At the beginning, the solution has a low pH and climbs as the strong base is added. As the solution nears the point where all of the H+ are neutralized, the pH rises sharply and then levels out again as the solution becomes more basic as more OH- ions are added.

The first curve shows a strong acid being titrated by a strong base. There is the initial slow rise in pH until the reaction nears the point where just enough base is added to neutralize all the initial acid. This point is called the equivalence point. For a strong acid/base reaction, this occurs at pH = 7. As the solution passes the equivalence point, the pH slows its increase where the solution approaches the pH of the titration solution.

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