Ijmb Model Questions Vol1 2022 Biology Question 3

A food sample is being analysed for its carbohydrate content using the Benedict’s test followed by spectrophotometric measurement at 420 nm. The procedure is as follows: 1. Prepare standard glucose solutions of known concentrations and record their absorbance values as shown in the table below. 2. Prepare an extract of the food sample by grinding 2.00 g of the sample, adding 50 mL distilled water, stirring for 5 min and filtering. 3. Pipette 10.0 mL of the extract into a test tube, add 5.0 mL of Benedict’s reagent, heat in a boiling water bath for 5 min, cool and measure the absorbance of the resulting solution. 4. Use the calibration curve obtained from the standards to determine the carbohydrate concentration in the test mixture and calculate the percentage carbohydrate in the original food sample. Standard data: | Glucose concentration (g dL⁻¹) | Absorbance (A) | |-------------------------------|----------------| | 0.00 | 0.00 | | 0.20 | 0.11 | | 0.40 | 0.23 | | 0.60 | 0.34 | | 0.80 | 0.46 | Absorbance of the test mixture: **0.29**.