Practical 11

Question 1

how can Benedict’s solution be used to measure the concentration of glucose in a solution

Answer 1

use a colorimeter to measure the absorbance of a series of solutions of known concentrations to create a calibration curve compare the absorbance of an unknown sample to the calibration curve

Question 2

what is a serial dilution

Answer 2

a dilution where successive concentrations increase or decrease in logarithmic fashion

Question 3

outline the procedure of this practical

Answer 3

1. make a serial dilution of glucose
2. place 2cm3 of each of the unknown samples in separate boiling tubes
3. add Benedict’s solution to all the boiling tubes
4. place boiling tubes in a water bath at 90c for four minutes
5. zero the colorimeter using a cuvette using distilled water and set o red filter
6. place known samples into cuvette and measure the absorbance of each using the colorimeter
7. make a calibration curve
8. measure the absorbance of the unknown samples using the colorimeter. use the calibration curve to determine glucose concentrations

Question 4

what are the axes in a calibration curve

Answer 4

absorbance against glucose concentration

Question 5

what would a high glucose concentration in urine suggest

Answer 5

it may suggest diabetes. lack of insulin leads to high BGC

Question 6

state the hazards and precautions of this practical

Answer 6

Benedict’s solution is an irritant, wear eye protection, avoid contact with skin.
handle the hot water bath with care

Question 7

how can you increase accuracy of the estimate of the unknown glucose solution

Answer 7

increase the number of concentrations for the calibration curve within the range of concentrations that the unknown belongs in