Core Practical 2

Question 1

Describe the aim of this practical

Answer 1

To investigate the vitamin C content of different fruit juices

Question 2

Explain why vitamin C is used in this practical

Answer 2

Vitamin C decolourises the blue dye DCPIP. This is because it is an antioxidant and acts as a reducing agent which reduces the DCPIP.

Question 3

Describe the IV, DV and CV

Answer 3

IV: Type of fruit juice
DV: Volume (cm^3) of fruit juice
CV: Temperature, Conc. of DCPIP, Volume of DCPIP and End point colour

Question 4

Describe the procedure of this practical

Answer 4

1. Pipette 1cm^3 of 1% of DCPIP into a test tube
2. Fill the burette with 1% of vitamin C solution. This solution must be used first to obtain a control value for concentration. Record the start volume (in cm^3) and turn on tap to add drops of vitamin C solution into the test tube and shake gently.
3. Continue drop by drop procedure of vitamin C solution until the instant the DCPIP solution goes from blue to colourless. Close the tap. Record the end volume and subtract the start volume from it to find the exact volume needed to decolourise DCPIP. Repeat 3 times to find an average titre volume to increase results accuracy.
4. Repeat the whole procedure with the different fruit juices
5. Calculate the mass of vitamin C required to decolourise 1 cm^3 of DCPIP solution. Use this value to work out how much vitamin C each of the fruit juices contain in mg cm^-3.

Question 5

Describe the risk assessment of this practical

Answer 5

• DCPIP may cause irritation to skin and eyes so goggles and gloves should be worn at all times
• Keep glass apparatus away from the edge of surfaces to avoid breaking
• If DCPIP solution spills, dilute with plenty of distilled water

Question 6

Explain the conclusion of this practical

Answer 6

The higher the concentration of vitamin C, the less volume of fruit juice required to decolourise DCPIP. Orange juice is the most beneficial drink to consume as it contains the highest concentration of vitamin C. Vitamin C is a reducing agent and provides hydrogen atoms that stabilise radicals in the body by pairing up with its unpaired electron. This can reduce cellular damage caused by the highly reactive nature of radicals. Therefore, orange juice proposes the lowest risk of CVD than any other fruit juice.