The objective of this experiment is to determine the vitamin C content of a lemon.
Aim: The objective of this experiment is to determine the vitamin C content of a lemon.
Apparatus: Lemon juice, vitamin C solution (fresh, 0.1%), 2 test tubes, test tube rack, pipette to measure 2.00 cm3 volume, DCPIP (dichlorophenolindophenol, 0.1% aqueous solution).
Procedure: The lemon juice and vitamin C solution were provided by the teacher. The vitamin C solution was made up to contain 0.001 g vitamin C in 1.0 cm3 water.
- Using a pipette, place exactly 2.00cm3 of DCPIP solution into a test tube.
- Using a different graduated pipette, add the vitamin C solution, drop by drop, to the DCPIP solution in the test tube. Shake the tube very gently after the addition of each drop of the vitamin C solution and continue adding drops until the DCPIP solution is decolorized.
- Record the exact volume of the vitamin C solution which has been added.
- Repeat this procedure. Average the results to obtain the mean volume of 0.1% vitamin C.
- Calculate the mass of vitamin C (in grams) in this volume of vitamin C solution. From that we obtain the amount of vitamin C required to decolorize 2cm3 of DCPIP.
- The next step is to find the volume of lemon juice which contains the equivalent mass of vitamin C. To find this, repeat steps (i)-(iii) using lemon juice (add the lemon juice drop by drop to 2cm3 of DCPIP solution in a test tube until it becomes decolorized. Record the exact volume of lemon juice added).
- Repeat Step (vi). Average the two results. This is the volume of lemon juice which contains the mass of vitamin C calculated in Step (v).
- Work out the mass of vitamin C in 1.00 cm3 of lemon juice.