Final Examination CHM260

In atomic spectroscopy, flame plays the most important role. State its function.

(FEB 2023)

• Letting light passes through a cloud of atoms.

• Supplying sufficient thermal energy to sample to dissociate ionic compounds into free

  atoms

• Focusing a beam of light into the atomic vapour for excitation to occur.

• Providing heat in burner for evaporation to occur.

Atomization is the most critical step in AAS, and it involves three processes. Select the correct statement that explains a NEBULIZATION process.
(JAN2024)

• A process to suck sample solution up the tube and into the nebulizer chamber.

• Solid atoms are converted to a vapour in the flame.

• The transformation of a liquid into a fine spray.

• Solid atoms are mixed with the gaseous fuel.

Select the following sequence of components in the CORRECT order for atomic emission spectroscopy (AES).

(JULY 2024)

• Nebulizer, Source, sample, burner, monochromator, detector, computer readout

• Burner, nebulizer, monochromator, detector, computer readout

• Burner, nebulizer, monochromator, computer, detector readout

• Nebulizer, burner, monochromator, detector, computer readout

In Atomic Absorption Spectroscopy (AAS), the hottest part of the flame is the best region for atomic absorption to occur. Name the region of flame.
(JAN 2024)

• Primary combustion region.

• Interzonal region.

• Secondary combustion region.

• Fuel oxidant mixture region.

Classify the type of interference involved in the analysis when two or more elements have emission spectra in adjacent or overlapping wavelengths.

(JULY 2024)

• Self-absorption

• Chemical Interference

• Ionization Interference

• Spectral Interference

In an AAS analysis of potassium, it was found that the concentration of potassium ions is

greater than the concentration of free potassium atoms. Choose the corrective technique from

the list.

(FEB 2023)

• More free atoms will be formed by the atomiser.

• Ions are reduced by using an ionisation suppressor.

• A chemical agent is useful in providing more atoms for excitation.

• Flame stability is very important in ensuring sufficient absorption occurs.

Predict which element is NOT suitable to be analysed using flame atomic absorption spectroscopy (FAAS).

(JULY 2024)

• Sodium

• Lead

• Potassium

• Uranium

Find a chromatographic technique classified under column chromatography.

(JULY 2024)

• Gas chromatography

• Paper chromatography

• Thin layer chromatography

• Stationary phase

Choose the CORRECT statement that describes the role of the mobile phase in chemical separation.

(JULY 2024)

• A process in which species are washed through a chromatographic column by the addition of fresh solvent

• The substance that moves over or through an immobilized phase that is fixed in place in a column or on the surface of a flat plate

• A solid or liquid that is fixed in place

• A technique used to separate and identify the components of a mixture

Name the term used for a chemically inert gas that is used in gas chromatography (GC).

(JULY 2024)

• Stationary phase

• Mobile phase

• Solvent

• Sample