Waec Model Questions Vol1 2024 Biology Question 3

Practice practical question 3 from the 2024 Waec Model Questions Vol1 Biology examination. This question covers Nutrition .

Waec Model Questions Vol1 2024 Biology Practical
Topic: Nutrition
Question 3 WAEC_MODEL_QUESTIONS_VOL1 • 2024 • BIOLOGY • practical

A student is required to determine the percentage carbohydrate in a 2.00 g sample of a commercial biscuit using the Benedict’s test. The student prepares a series of glucose standard solutions (0.2 g, 0.4 g, 0.6 g of glucose dissolved each in 100.0 mL water) and records the absorbance of the resulting coloured solutions at 540 nm after adding Benedict’s reagent and heating for 5 minutes. The absorbance readings obtained are: 0.2 g – 0.150, 0.4 g – 0.310, 0.6 g – 0.470. The biscuit extract is prepared by weighing 2.00 g of biscuit, adding 50.0 mL of distilled water, heating for 10 minutes, filtering and making the final volume up to 100.0 mL. The absorbance of the biscuit solution after the same treatment is 0.385.

Question Parts

( a )
State the purpose of preparing the glucose standard solutions and explain how they are used to determine the carbohydrate content of the biscuit.
( b )
Using the three standard absorbance values, construct the best‑fit straight‑line equation (assume a linear relationship) and then calculate the mass of glucose equivalent present in the biscuit extract.
( c )
From the mass of glucose equivalent obtained in part (b), calculate the percentage carbohydrate (by mass) in the original biscuit sample.
( d )
Identify two possible sources of systematic error in this experiment and suggest a way to minimise each.

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About This Question

This is Waec Model Questions Vol1 2024 Biology Question 3. It is one of the practical questions from the 2024 Waec Model Questions Vol1 Biology examination.

The question covers Nutrition .

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