Titration is a sensitive analytical method that lets you determine an unknown concentration of a chemical in solution by introducing a known concentration of another chemical. 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. As sensitive as the method is, several factors can cause errors in titration findings.
End Point Error
The end point of a titration is when the reaction between the two solutions has stopped. Indicators, which change color to indicate when the reaction has stopped, do not change instantly. In the case of acid-base titration, the indicator may first lighten in color before changing completely. Also, each individual perceives color slightly differently, which affects the outcome of the experiment. If the color has changed slightly, too much of the titrant, which comes from the burette, can be introduced into the solution, overshooting results.
Misreading the Volume
The accuracy of titration depends upon the accuracy of the known concentration change. But markings on a burette can be 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 apparent 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.
Errors in concentrations directly affect the measurement accuracy. Errors include using the wrong concentration to begin with. This can occur because a titrant decomposes or evaporated over time. The solution may have been prepared incorrectly or other items could have been introduced into the solution, such as using dirty equipment that affects concentration levels. Cleaning equipment with the wrong solution also can affect the concentrations of the solutions to be experimented on.
Using the Equipment Incorrectly
You must follow strict guidelines in 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 affect results. Errors in filling the burette can cause air bubbles, which can affect the flow of the titrant.
Other human or equipment error can also creep in. Human error includes using selecting 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.