Qualitative Spectral analysis

What is spectral analysis ?

physical method for qualitative and quantitative determination of the composition of different substances by studying the energy of the light absorbed, scattered, reflected or emitted by them within a certain wavelength range

What is absorption spectra ?

Investigation of light absorption of different wavelengths by substances to determine their composition

How is the absorption spectra obtained?

When light with continuous spectrum traverses the sample, and part of its energy at specific wavelengths is absorbed by the sample

Describe emission spectra ?

Investigation of light emission at different wavelengths by substances

How is emission spectra obtained?

Substance is subjected to preliminary excitation. Resulting in specific radiant fluxes at particular wavelengths

What is scattering spectra ?

light energy scattered by the substance under investigation at different wavelengths

Define reflection spectra

light energy reflected by the substance under investigation at different wavelengths

Define Kirchhoff’s law

What info do absorption and emission provide

equivalent information

Define qualitative spectral analysis

The sort of substance contained in a sample can be determined from its spectra

Define quantitative spectral analysis

The amount of energy absorbed or emitted by a substance depends on the number of emitting particles, so if that same amount is determined for one or more wavelengths one can obtain info about tthe concentration of substances

When the thickness of the absorbing layer increases…

the absorption bands become darker and darker

2 factors that affect absorption spectra

solute concentration and the kind of solvent

What are the six groups that spectral analysis be divided into depending on the substance composition being studied?

Atomic , ,molecular , continuous , monochromatic , line , band spectrum

What is atomic spectral analysis

elementary composition of subtances. Both emission and absorption spectra used

What is molecular spectral analysis

molecular composition of substances. Predominantly absorption spectra used

describe continuous spectrum

radiant flux contains rays of all wavelengths. The emission spectra of all heated bodies are continuous

Define the monochromatic spectrum ?

Radiant flux contains rays of a single wavelength only

Define line spectrum ?

radiation consisting of a finite number of monochromatic waves e,g non separating atoms

Define band spectrum ?

Radiant flux may contain many closely spaced lines forming bands. This is the spectra in chemical compounds

What do spectral instruments do?

disperse electromagnetic radiation according to wavelength

The two main functions of a spectral instrument?

1 . Dispersing element 2. Create spectrum

The dispersing element may be a …

prism or a diffraction grating

Name 3 types of spectral instruments

monochromators , spectroscopes, mass spectrometers

What is an optical monochromator

produces monochromatic light, where a prism spreads out the light according to its wavelength. After the optical lens collects the rays, a slit located on the focal plane of the lens isolates a narrow band

Spectroscope and spectrograph

an entire obtained spectrum can be viewed here from the focal plane of the lens

Spectrometer

Allow quantitative measurement of the radiation at various wavelengths. This can be achieved if a photodetector is placed in the focal plane to measure the intensity of light.