Analytical Techniques

Question 1

Spectroscopy: Emission

Answer 1

Occurs when excited electrons return to their ground states and radiate energy of fixed wavelengths. Emission spectra have coloured lines on a black background.

Question 2

Spectroscopy: Absorption

Answer 2

Molecules can absorb energy of specific wavelengths. If this occurs in the visible spectrum then the substance will appear coloured. Absorption spectra are the reverse of emission spectra, with dark lines on a rainbow spectrum.

Question 3

Spectroscopy: Absorbance

Answer 3

The intensity of light remaining after some has been absorbed, compared with the intensity of light when none has been absorbed.

Question 4

Spectroscopy: Transmittance

Answer 4

A measurement of the proportion of light that has been transmitted through a substance, where 100% transmittance means that no energy has been absorbed.

Question 5

Spectroscopy: Spectrometer

Answer 5

An instrument that measures the light emitted or absorbed by excited electrons or molecules. The colorimeter (aka photometer), atomic absorption spectrometer and the UV-visible spectrophotometer measure absorbance. The infrared (IR) spectrophotometer measures transmittance.

Question 6

Spectroscopy: Wavelength

Answer 6

Distance between the same point on two successive waves

Question 7

Spectroscopy: Frequency

Answer 7

Number of waves that pass a given point in one second. Measured in Hertz (Hz).

Question 8

Spectroscopy: Colorimetry

Answer 8

a method of determining the concentration of the analyte by measuring the relative absorption of light (usually visible) compared to solutions containing known concentrations of that substance.

Question 9

Spectroscopy: Cuvette

Answer 9

A cell used to hold the analyte in spectroscopic analysis

Question 10

Spectroscopy: Calibration Curve

Answer 10

A plot of the results of an experiment at a range of known concentrations, so that these can be compared with an experiment using an unknown concentration within that range.

Question 11

Spectroscopy: UV-Visible Spectrometry function

Answer 11

A more sophisticated analysis technique than colorimetry, but using a similar principle. A monochromator is used to produce a single wavelength of light in the visible or UV spectrum and the absorbance of the analyte at that wavelength is measured.

Question 12

Qualitative data

Answer 12

Qualitative data is descriptive. content. (it describes something)

Question 13

Quantitative data

Answer 13

Quantitative data is numerical. content (numbers)