MC test: Vitamins

Multiple choice test on B.5 Vitamins

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

Which vitamins are fat-soluble?

I. vitamin A 

II. vitamin C 

III. vitamin D  

Vitamin C is water-soluble as it contains many polar -OH groups. Vitamins A and D only contain one polar group and are largely made up of non-polar hydrocarbon chains and rings.

 

Which vitamin is synthesised in the body using sunlight?

 

Vitamin D is formed by the action of sunlight on cholesterol in the skin.

 

Which functional groups are present in vitamin A ?

I. alkenyl

II. hydroxyl

III. phenyl

Although it does contain a six-membered carbon ring, vitamin A does not contain a C6H5− (phenyl) group.

 

Which vitamin helps to regulate the amount of calcium and phosphate in the human body?

Lack of vitamin D causes 'rickets' due to a lack of calcium and phosphate which are required for healthy bones.

 

In the past sailors on long sea voyages used to suffer from 'scurvy'. What was the cause of this disease?

Scurvy is caused by a lack of vitamin C. Vitamin C is found in fruit and vegetables. As it is water soluble it is not retained by the body so needs to be continually imbibed.

 

Which are correct statements about vitamins?

I. Most vitamins are sensitive to heat.

II. Most vitamins cannot be synthesised by the human body.

III. Vitamins are organic micronutrients obtained from suitable food sources.

Vitamin D can be synthesised by the human body, but most vitamins cannot, and most are decomposed by heating.

 

Which are properties of vitamin C?

I. It is readily oxidised.

II. It is acidic.

III. It is an antioxidant.

Vitamin C (ascorbic acid) is acidic, it can be readily oxidised to dihydroascorbic acid (giving up two protons and two electrons in the process) and functions as an antioxidant by helping to eliminate free radicals produced in the body.

 

Which vitamin deficiency can lead to abnormal dryness of the conjunctiva and cornea of the eye (xerophthalmia)?

Vitamin A promotes good vision, especially in low light. A lack of vitamin A can lead to xerophthalmia which can cause blindness.

 

Why do many people in Australia and New Zealand suffer from vitamin D deficiency?

Vitamin D is fat-soluble and is added by law to edible oils and spreads in Australia to combat the lack of vitamin D caused by underexposure to direct sunlight to avoid skin cancer.

 

The molar mass of vitamin C is 176 g mol−1. The percentage of vitamin C in a vitamin tablet can be determined by titration with iodine solution.

C6H8O6(aq) + I2(aq) → C6H6O6(aq) + 2H+(aq) + 2I−(aq)

It requires 20.0 cm3 of 0.100 mol dm−3 iodine solution to react exactly with a solution made by dissolving a vitamin tablet with a mass of 1.00 g in 100.0 cm3 of water.
What is the percentage of vitamin C in the tablet? Assume nothing else in the tablet reacts with iodine.

Amount of iodine used = (20.0 ÷ 1000) x 0.100 = 0.002 mol.
Since 1 mol of vitamin C reacts with 1 mol of I2, the amount of vitamin C = 0.002 mol.
Mass of vitamin C in 1.00 g of tablet = 0.002 x 176 = 0.352 g
Percentage of vitamin C in the table = (0.352 ÷ 1.00) x 100 = 35.2%

 

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