Experiment 1

Question 1

Detection of Alcohol

Answer 1

Relies on the reduction of the orange-coloured dichromate ion, Cr2O7^2-, (Cr^6+), to the blue-green chromium ion, Cr^3+. In most cases the resulting solution is a mixture of dichromate and chromium ions, giving a golden yellow colour.

Question 2

Beer’s Law

Answer 2

A = Ɛlc

Question 3

A

Answer 3

Absorbance. A measure of how much light the solution absorbs.

Question 4

Ɛ

Answer 4

Molar absorptivity (in M^-1 cm^-1). A proportionality constant that is characteristic of the coloured substance and varies with wavelength.

Question 5

l

Answer 5

Path length of light through the solution (in cm). Is the inner diameter of the sample cuvette.

Question 6

c

Answer 6

Molar concentration of solute (in M).

Question 7

Standard Curve

Answer 7

Created by plotting the absorbance and the concentration for a series of standard solutions.

Question 8

Spectrophotometer

Answer 8

Used to measure a solution’s absorbance at a specific wavelength.

Question 9

λmax

Answer 9

The wavelength of light that is absorbed most strongly by that sample.

Question 10

Incident Light (Io)

Answer 10

The amount of light entering the sample.

Question 11

Transmitted Light (It)

Answer 11

The light that leaves the solution and hits the detector.

Question 12

Detector

Answer 12

A photocell or phototube which produces a voltage that is proportional to the light intensity. The voltage can be displayed as absorbance or transmittance.

Question 13

Blank

Answer 13

Contains the solvent only, ie. everything except the substance that we are interested in measuring.

Question 14

Acidic Potassium Dichromate Solution

Answer 14

Very corrosive and is a strong oxidizer. Wear gloves when handling this solution.

Question 15

Experiment 1 Summary

Answer 15

1) Create ethanol standards using 0.150% ethanol and dH2O.
2) Make a dilute version of the wine sample by transferring 1.00 mL of the wine into a 100.00 mL volumetric flask.
3) There are a total of 7 test tubes, each contain 2.00 mL of the acidic potassium dichromate solution and 2.00 mL of their designated solution (ethanol, water, or wine).
4) Heat test tubes in a hot water bath for 10 minutes before filling cuvettes.
5) Take the readings of the cuvettes.
6) Coloured solutions and their rinses go in the waste container at the spectrophotometer. Colourless solutions go down the sink.