Colorimetry & Calibration Curves

Question 1

What is a Colorimeter?

Answer 1

an instrument to quantitatively measure the intensity of colour of a solution

Question 2

What is a cuvette?

Answer 2

a special rectangular test tube that has a light source and detector which measures absorbance and transmission (how much light has gone through)

Question 3

What do you use a blank for?

Answer 3

e.g. a cuvette filled with distilled water to zero each reading

Question 4

What is a calibration curve?

Answer 4

a method for determining the concentration of an unknown solution by comparing it to a range of known concentrations

Question 5

What are the steps for calibration curve?

Answer 5

• use serial dilutions of known concentrations of reducing sugar
• heat with an excess of benedict’s solution
• Use the same volumes of solutions each time
• Colour change ( blue -> green -> yellow -> red)
• Zero colorimeter using a blank e.g. H2O + Benedict’s
• Read results using transmission / absorption
• Plot the data on a graph = calibration curve
• Test unknown sugar in same way