GPC 1

Which statement best describes the principle of chromatography?

• A method to identify chemical structures.

• A technique to separate components in a mixture using their distribution between two phases.

• A method used to increase the concentration of an analyte.

• A process to determine molecular weight.

What is the function of the stationary phase in chromatography?

• To move analytes through the column.

• To provide a medium for analytes to interact and separate.

• To increase the velocity of the mobile phase.

• To detect the analyte concentration.

Why are sharp and symmetrical peaks desirable in chromatography?

• They reduce retention time.

• They improve qualitative and quantitative analysis.

• They help increase sample size.

• They minimize the void volume.

If the stationary phase strongly interacts with a solute, what will happen to the solute’s retention time?

• It will increase.

• It will decrease.

• It will remain constant.

• It depends on the mobile phase composition.

Calculate the number of theoretical plates (N) if the column length (L) is 25 cm and the plate height (H) is 0.05 cm.

• 500

• 100

• 1250

• 250

What adjustment would you make to reduce band broadening caused by longitudinal diffusion?

• Increase the flow rate of the mobile phase.

• Decrease the temperature of the system.

• Use a larger particle size in the column.

• Reduce the mobile phase flow rate.

A solute is showing fronting in its chromatographic peak. What could be a likely cause?

• A high flow rate of the mobile phase.

• Sample concentration is too high

• Insufficient interaction with the stationary phase.

• The detector is malfunctioning.

Which theory assumes that solutes equilibrate instantly between phases in a column?

• Plate theory

• Rate theory

• Partition theory

• Diffusion theory

What does the van Deemter equation help optimize?

• The detection limit of the chromatogram.

• The selectivity of the stationary phase.

• The flow rate for minimum plate height (Hmin).
  

• The size of analyte bands on the chromatogram.