Neco 2022 Biology Question 3

A group of students carried out an investigation to determine the carbohydrate content of three food samples (A: white rice, B: banana, C: boiled potatoes) using the iodine colour test and a spectrophotometer. They prepared standard glucose solutions of known concentrations (0, 2, 4, 6 and 8 g per 100 mL) and recorded the absorbance at 620 nm as follows: 0.00, 0.12, 0.24, 0.36 and 0.48 respectively. The extracts of the food samples gave absorbance readings of 0.30 (A), 0.18 (B) and 0.42 (C). For each extract, 10 mL of the solution was placed in the cuvette for measurement. The extracts were prepared by weighing 10 g of each food, adding 100 mL of distilled water, heating, filtering and making up to 100 mL.