Waec Model Questions Vol1 2021 Biology Question 3

A group of students carried out a quantitative analysis of carbohydrate in a cooked rice sample using the Benedict’s test. The procedure was as follows: 10 g of the cooked rice was homogenised in 100 mL of distilled water, filtered and the filtrate was made up to the mark. From this solution, 10 mL was taken and mixed with an excess of Benedict’s reagent. The mixture was heated in a water‑bath for 5 minutes and the volume of Benedict’s reagent required to give the first distinct brick‑red colour was recorded. The data obtained from a series of glucose standards are shown in the table below. | Glucose (mg) | Volume of Benedict’s reagent (mL) | |--------------|-----------------------------------| | 0 | 5.0 | | 200 | 7.0 | | 400 | 9.0 | | 600 | 11.0 | The rice sample required 9.5 mL of Benedict’s reagent to develop the colour.