Answers To Mid Year Biology Paper 3 - Question 2

Problem Statement
Which fruit juice contains the highest concentration/percentage of Vitamin C?

Objective of investigation
To determine the vitamin C content in pineapple, lime and guava (take from the question).

Hypothesis
Lime juice contains higher concentration/percentage of vitamin C compared to pineapple juice and guava juice.

Variables
Manipulated : Types of fruit juice
Responding : Concentration/percentage of vitamin C in fruit juices
Constant : Volume of fruit juices/concentration of DCPIP solution/ Standard
concentration of ascorbic acid solution

Material & Apparatus
Materials : freshly prepared pineapple, lime and guava juices, 0.1% ascorbic acid solution, DCPIP solution
Apparatus : 5ml syringe(with needle), 1ml syringe, specimen tubes, 5ml measuring cylinder

Technique
Measure and record the volume of fruit juice needed to decolourise 1 ml DCPIP using a syringe//

Calculate the concentration of vitamin C in fruit juice by using formula :
Volume of 0.1% ascorbic acid to decolorise 1 ml DCPIP X 1.0 (mgcm-3)
volume of fruit juice needed to to decolorise 1 ml DCPIP


or Calculate percentage of vitamin C in fruit juice by using formula :
Volume of 0.1% ascorbic acid to decolorise 1 ml DCPIP X 0.1%
volume of fruit juice needed to to decolorise 1 ml DCPIP


Procedure
1. 1 ml of DCPIP solution is placed in a specimen tube using a 1 ml syringe.
2. 5 ml syringe was filled with 5 ml of 0.1% ascorbic acid solution.
3. The needle of the 5 ml syringe was immersed into the DCPIP solution.
4. Ascorbic acid solution was added drop by drop until the DCPIP solution, and gently stirred with the needle of the syringe. (Do not shake the tube vigorously).
5. Ascorbic acid solution is added continuously until the DCPIP solution is decolourise.
6. The volume of ascorbic acid solution used is recorded.
7. Steps 1-6 are repeated using fresh guava, pineapple and lime juice.
8. The volume of fruit juices required to decolourise the DCPIP solution in each fruit juice is recorded in a table.
9. The percentage and the concentration of vitamin C in each fruit juice are calculated.


Presentation of Data

Solution/ fruit juice	Volume of solution/fruit juice needed to decolourise 1 ml of DCPIP solution (ml)	Percentage of vitamin C (%)	Concentration of vitamin C (mg cm -3)
0.1% ascorbic acid	Table Cell	Table Cell	Table Cell
Pineapple juice	Table Cell	Table Cell	Table Cell
Lime juice	Table Cell	Table Cell	Table Cell
Guava juice	Table Cell	Table Cell	Table Cell

Conclusion
Lime juice contains higher concentration/percentage of vitamin C compared to pineapple juice and guava juice. Hypothesis is accepted.