Errors in titration experiments

Written by michael e carpenter
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According to Purdue University, "A titration is a technique where a solution of known concentration is used to determine the concentration of an unknown solution." The solution of the known concentration is introduced into a specific volume of the unknown through a burette or pipette. Indicators are used to determine when a reaction has come to an end. Titration findings are not always accurate. Errors in the finding are common and occur for many reasons.

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End Point Error

The end point of a titration is when the reaction between the two solutions has stopped. Indicators, which change colour to indicate when the reaction has stopped, do not change instantly. In the case of acid-base titration, the indicator may first lighten in colour before changing completely. Also, each individual perceives colour slightly differently, which affects the outcome of the experiment. If the colour has changed slightly, too much of the titrant, which comes from the burette, can be introduced into the solution, overshooting results.

Misreading the Volume

On a titration, it is vital to have the exact amount of titrant being introduced into the unknown solution. The markings on the burette are easily misread. One way to misread the volume is by looking at the measurement on an angle. If looking from above, it seems like the volume is lower. If looking from below, the volume is higher. Another source of measurement error is looking at the wrong spot. A solution forms a concave curve and the bottom of the curve is used to measure the volume. If the reading is taken from the higher sections of the curve, the volume measurement is in error.

Concentrations

There are many errors regarding concentrations of the substances being titrated. Errors include using the wrong concentration to begin with. This can occur because a titrant decomposes or evaporated over time. The solution was prepaid incorrectly or other items were introduced into the solution, such as using dirty equipment that affect concentration levels. Cleaning equipment with the wrong solution also can affect the concentrations of the solutions to be experimented on.

Using the Equipment Incorrectly

The person must follow strict guidelines to handling and using all equipment during the experiment. The slightest mistake will create errors in the findings. For example, swirling the solution can result in loss of solution and will effect results. Other errors include not filling the burette properly can cause air bubbles, which can affect the flow of the titrant.

Other Errors

Any numbers of errors can occur during titration that are either human or equipment error. Human error includes using the wrong reagents or using the wrong amount of indicator and rinsing materials after solution transfer. Equipment error typically is in the burette, which can develop leaks over time. Even a small loss of fluid will affect the results of the titration.

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