Analysis of Vitamin C content of Soft Fruit Drinks - Coursework Example

Titration is a commonly performed experiment which is used to determine the exact concentration of a particular substance in solution. This is achieved by adding increasing amounts of a standard solution of known concentration (the titrant) to a measured quantity of the solution whose concentration one intends to ascertain (the analyte), and determining the end point of the reaction by means of a substance termed as an indicator. Titration can be used to determine the concentration of various substances including several acids and bases.

Vitamin C has been found to turn a blue dye clear. Thus, the amount of Vitamin C in a solution can be worked out by titrating the different soft drinks against a fixed amount of the blue dye, which serves as both the titrant and the indicator in this experiment.  Materials Available: Blue dye A solution containing a known amount of Vitamin C (Solution A) A selection of old products: a lemon, orange and blackcurrant drink A selection of new products: a lemon, orange and blackcurrant drink Equipment needed: Burette Pipette, graduated Pipette filler Ehrlenmeyer flask or Beaker Distilled water Burette clamp Stirring rod Procedure: To begin the experiment, the amount of solution which has a known quantity of Vitamin C (labeled as Solution A) needed to turn 1 cm3 of the blue dye colorless has to be determined.

To achieve this, a measured quantity, i.e. 1 cm3 of the dye is added to an Ehrlenmeyer flask or beaker with the help of a pipette. Before using the pipette, it is important to ensure that it is thoroughly cleaned and conditioned before being used in order to remove any water droplets or impurities. Conditioning is achieved by rinsing the pipette with a small volume of the solution being transferred (the stock solution) and disposing of the rinsing solution. The pipette is then filled up to the calibration mark with the help of a pipette filler.

It is important to remember that most solutions would form a concave meniscus. Thus, while reading a meniscus, the bottom of the meniscus should be read and the meniscus should be kept at eye level in order to avoid parallax errors. Moreover, the meniscus should be read against a uniform background, which can be achieved by placing a white sheet of paper behind the level of the liquid. The dye is now transferred to the conical flask. Once all the solution has drained, the experimenter should touch the tip of the pipette to the side of the flask.

This helps in removing the last drop of solution from the pipette and helps in avoiding errors. It is important to keep in mind that one does not need to blow the last drop of solution out of the pipette. As pointed out previously, in this experiment the blue dye serves as both the titrant and the indicator. An indicator is a substance which indicates the pH of a substance and is commonly used to determine the end point of a reaction, which is denoted by a color change of the indicator. The next step is to add the solution A into the beaker drop by drop by means of a burette.

The burette is an apparatus which helps in slowly and precisely deliver small measured volumes of a solution to another. It is most commonly used in titration experiments and measures solutions up to an accuracy of