Question

Chromatography Basics Multiple Choice: Answer the following multiple choice questions about Chromatography Basics  (SHOW WORKING):

1) In a given chromatographic column,

A) different solutes behave as if there are a different number of theoretical plates for each.

B) the number of theoretical plates is the same for all solutes.

C) efficiency is improved by increasing plate height.

2) What useful information can be found from a Van Deemter plot?

A) The selectivity factor

B) Optimum mobile phase flow rate

C) Optimum column temperature

D) Type of stationary phase being used

3) In a gas chromatography experiment using a non-polar stationary phase

A) solutes are eluted in order of increasing boiling point.

B) solutes are eluted in order of increasing vapor pressure.

C) solutes are eluted in order of increasing polarity.

4) In which type of chromatograph is the interaction between the analyte and the stationary phase due to the size of the molecule only?

A) adsorption chromatography

B) partition chromatography

C) gel permeation chromatography

5) Which is the most common carrier gas for gas chromatography?

A) helium

B) nitrogen

C) hydrogen

Answer 1

1.ans :A) different solutes behave as if there are a different number of theoretical plates for each.

Reason :When there is more theorital plates than narrower the band width therfore thus it gives better resolution.

2..ans :B) Optimum mobile phase flow rate

Reason :

As per The Van Deemter equation in chromatography relates the variance per unit length of a separation column to the linear mobile phase velocity by considering physical, kinetic, and thermodynamic properties of a separation.

the mobile phase velocity is taken as the exit velocity, that is, the ratio of the flow rate in ml/second to the cross-sectional area of the ‘column-exit flow .

3.ans :A) solutes are eluted in order of increasing boiling point.

Reason :

In gas chromatography

Nonpolar Stationary Phase

- Solutes are eluted in order of increasing boiling point

- Solutes with higher vapor pressure are eluted faster

Polar Stationary Phase

- Solutes are separated based on polarity

- Less polar solutes are eluted faster than

strongly polar solutes

4.Ans :C) gel permeation chromatography

The chromatographic method in which molecules in solution are separated by their size, and in some cases molecular weight is known as Size-exclusion chromatography

when an aqueous solution is used to transport the sample through the column, the technique is known as gel-filtration chromatography or gel permeation chromatography​.

5.Ans A) helium

Reason :In gas chromatography, the Mobile phase is a carrier gas, usually an inert gas such as Helium or Nitrogen. Helium remains the most commonly used carrier gas in about 90% of instruments although hydrogen is preferred for improved separations.

Answer 2

correct options are:

1. a

2. b

3. a

4. c

5. a
   

Answer 3

Number one is A.