Neco Model Questions Vol1 2020 Biology Question 3

A student is determining the carbohydrate content of an unknown food sample using the dinitrosalicylic acid (DNS) colourimetric method. The procedure involves preparing standard glucose solutions, measuring their absorbance at 540 nm, plotting a calibration curve and then analysing the unknown sample. The data obtained are shown in the table below. | Standard glucose concentration (g dL⁻¹) | Absorbance (A) | |------------------------------------------|----------------| | 0.20 | 0.12 | | 0.40 | 0.24 | | 0.60 | 0.36 | | 0.80 | 0.48 | The absorbance of the unknown sample solution was recorded as 0.30. The unknown food sample (2.5 g) was extracted with water and the extract was diluted to a final volume of 100 mL before the DNS assay. Answer the following: