CHE301 Final Term Past Papers Fall 2020 by Amaan Khan

CHE 301 Final Term Current Fall 2020

Qno1: What type of energy occur when energy absorb by ion or molecule?

There are various types of electromagnetic radiation, there are various types. Depending on the energy of the photon absorbed or emitted, different phenomena can occur. When an atom absorbs an UV photon or a photon of visible light, the energy of that, Hence, the color observed is of the metal ion only.

Qno2: What happened when condensed ring increase?

As the number of condensed rings increases, the absorption is shifted progressively to longer wavelength.

Qno3: Differentiate between partition coefficient and distribution coefficient?

The success of this method depends upon the difference in solubility of a compound in various solvents. For a given compound solubility differences between solvents is quantified as the "distribution coefficient"

When a compound is shaken in a separatory funnel with two immiscible solvents, the compound will distribute itself between the two solvents. It is known as partition coefficient. Qno4: Write three application of IR spectroscopy.

Applications of IR Spectroscopy

1. Structure Determination

Search for benzene ring presence. Search for functional groupregions (carbonyl, NH, OH, CO etc.) • Search for CH of different types.

2. Identification of compound

• Matching given structure (metal, complex formation)
• Matching of standard through finger print region
• Differentiate if we have alcohol or ether

3. Progress of reaction

• Oxidation of secondary alcohol to ketone
• Reduction of alcohol to alkene
• Hydrolysis of sugars

Qno5: Write down the type or source used in IR spectroscopy.

Radiation Source:

• Nernest filament is composed of a mixture of oxides of zirconium, thorium and yttrium, which is formed into a hollow rod about 2 mm in diameter and 2-5 cm in length.
• Globar is a bonded silicon carbide rod about 7 mm in diameter and 5 cm in length.

Qno6: What is flash chromatography.

Flash Chromatography:

In flash column chromatography the sample is pumped through the packed glass column. Flash silica has quite smaller mesh size. Qno7: Explain the function of ICP.

ICP (Inductively Coupled Plasma) Spectroscopy is an analytical method used to detect and measure elements to analyze chemical samples. The process is based on the ionization of a sample by extremely hot plasma, usually made from argon gas.

Qno8: What are the types of Sorbents?

Polar Sorbent:

POLAR INTERACTION

• Also called hydrophilic or normal phase
• Involves hydrogen bonding, pi-pi and dipole/ dipole interactions
• Sorbents - silica, diol, diethylamino, cyanopropyl
• Applications - lipids, oil additives, carbohydrates, phenols, oil soluble vitamins.

Non-Polar Sorbent:

• It is also called reverse phased.
• Where polar silica’s ends are replaced with nonpolar carbon chain.
• Same as in HPLC.

Ion exchange sorbent:

• Cation exchange resins are negatively charged and adsorb positively charged cations from matrix.
• Anion exchange resins are positively charged and adsorb negatively charged conjugate bases from matrix.

Copolymeric sorbent:

Hydrophobic & ionic retention mechanisms. Reverse phase sorbent with cation or anion exchange.

Acidic, basic & neutral analyte applications. Matrix aqueous. Elution solvents mixture of organics with acid or bas. Qno9: Explain the chiral chromatography.

CHIRAL CHROMATOGRAPHY

Special chemically modified stationary phases, for example cellulose or amylose derivatives, proteins or peptides, cyclodextrins etc., for the separation of enantiomers

Most separations are based upon partition mechanisms utilizing chemically modified silica as the stationary phase and polar solvents as the mobile phase. The surface of the support, for example the silanol groups of silica, is reacted with various silane reagents to produce covalently bound silyl derivatives covering a varying number of active sites on the surface of the support. The nature of the bonded phase is an important parameter for determining the separation properties of the chromatographic system. Qno10: Name of the detectors used in Spectroscopy.

1. Photomultiplier tubes
2. UV/Vis Spectrophotometers
3. Phototube
4. Diode array detector

Qno11: Dimensions of column.

Classification of Column Dimensions:

Standard column: Diameter 4.6 mm, length 15 to 25 cm