The objective of this experiment is to determine the vitamin C content of a lemon.

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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.

  1. Using a pipette, place exactly 2.00cm3 of DCPIP solution into a test tube.
  2. 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.
  3. Record the exact volume of the vitamin C solution which has been added.
  4. Repeat this procedure. Average the results to obtain the mean volume of 0.1% vitamin C.
  5. 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.
  6. 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).
  7. 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).
  8. Work out the mass of vitamin C in 1.00 cm3 of lemon juice.
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Data Collection:

Data Analysis:

To calculate the amount of vitamin C in 1.12 mL of vitamin C solution:

Since the solution contains 1 mg of vitamin C in 1.00 mL, 1.12 mL of the vitamin C solution contain 1.12 mg of vitamin C.

To calculate the content of vitamin C in 1.40 mL of lemon juice:

The volume of lemon juice in a typical lemon is approximately 120 mL.

1.12 mg * 120 mL / 1.41 mL = 95.3 mg vitamin C / lemon

Conclusion: The major source of error in this investigation is that ...

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