Which chromatography technique uses inert carrier gas as the mobile phase?

Gas-liquid chromatography (GLC)

Thin-layer chromatography (TLC)

What is the primary purpose of chromatography?

To separate and identify different substances in a mixture

To measure the temperature of a substance

To determine the mass of a substance

To purify a single substance without separation

What is the initial step when preparing the filter paper for paper chromatography?

Drawing a pencil line near the bottom of the sheet

Submerging it completely in the solvent

Drawing a pencil line near the top of the sheet

Adding the sample of ink directly to the solvent

Why is a lid placed on the beaker during a paper chromatography experiment?

To stop the solvent from evaporating

To prevent the paper from falling out

To increase the rate of solvent movement

To keep the ink sample concentrated

Which formula correctly defines the Rf value in paper chromatography?

Distance travelled by the substance / Distance travelled by the solvent

Distance travelled by the solvent / Distance travelled by the substance

Mass of the substance / Mass of the solvent

Time taken by the substance / Time taken by the solvent

A high R f value indicates strong

strong affinity to the mobile phase

strong affinity to the stationary phase

no affinity to the stationary phase

What is the correct way to draw lines on a TLC plate?

Draw lines lightly with a pencil to avoid scratching the silica

Draw lines firmly with a pen to ensure visibility

Draw lines 2 cm from the bottom and 4 cm above the first line

Do not draw any lines, as they interfere with the separation

How should a sample be applied to the TLC plate to achieve maximum resolution?

Use multiple brief touches with a microcapillary tube to create a small, concentrated spot

Apply a large, single drop of sample to the start line

Apply the sample by drawing a continuous line across the start line

Apply the sample directly to the finish line

Why is visualization necessary for most organic compounds after running a TLC?

They are typically invisible to the naked eye.

They are usually colored and difficult to distinguish.

They evaporate quickly after the TLC is run.

They react with the TLC plate if not visualized immediately.

What is a key advantage of using UV light for visualizing TLC spots compared to chemical stains?

UV light is non-destructive, allowing for further analysis of the compounds.

UV light is more sensitive and can detect smaller amounts of compounds.

UV light produces more vibrant and distinct colors.

UV light is faster and requires less equipment.

How does UV light help visualize organic compounds on a TLC plate?

Compounds that absorb UV light prevent the fluorescent material on the plate from glowing, creating dark spots.

It causes all organic compounds to glow brightly.

It reacts chemically with the compounds to produce color.

The UV light directly illuminates the compounds, making them visible.

Compare the stationary phase used in paper chromatography and thin-layer chromatography (TLC).

Paper chromatography uses paper, TLC uses a thin layer of oxide on a plate.

Paper chromatography uses silica gel, TLC uses paper.

Both use glass plates as stationary phase.

Both use aluminium oxide as stationary phase.

A chemist tries to separate a mixture of four aldehydes using TLC. What difficulty is she likely to have?

They will probably have very similar Rf values

Not many solvents will dissolve aldehydes

All aldehydes are highly volatile - they'll evaporate

They will adsorb too strongly to the stationary phase

What is the first physical step when preparing a chromatography column?

Inserting a small cotton plug at the bottom.

Filling the column with solvent.

Adding a layer of sand to the bottom.

Pouring the silica gel slurry into the column.

Why is it crucial for the sample to be concentrated in a thin band at the top of the stationary phase when loading a chromatography column?

To ensure efficient separation of components.

To prevent the solvent from evaporating too quickly.

To make the column visually appealing.

To reduce the amount of solvent needed for elution.

What is a critical rule to follow when adding solvent to a chromatography column to prevent ruining the column?

Ensure the solvent level never drops below the sand or stationary phase.

Always add solvent quickly to ensure a fast flow rate.

Pour the solvent directly onto the center of the sand bed.

Only use a pipette for all solvent additions, never a beaker.

When collecting organic material during column chromatography, why is it advisable to reduce the volume of each fraction?

To maximize the chances of a clean separation.

To make the fractions easier to handle.

To speed up the overall collection process.

Why is it important to use small fractions when a product is expected to exit the column, especially when analyzing by TLC?

To minimize the amount of desired product wasted due to impurity overlap.

To ensure that the solvent evaporates faster.

To prevent the column from drying out.

To make it easier to number the flasks.

Why is column chromatography used in a laboratory setting?

To separate a desired product from unwanted side products and impurities.

To speed up chemical reactions.

To analyze the purity of a single compound.

To synthesize new chemical compounds.

Which of the following best describes the mobile phase in column chromatography?

A liquid or gas that carries the sample through the column

A solid that remains fixed in the column

A gel that reacts with the sample

A powder that absorbs the sample

What is a real-world application of column chromatography?

Purification of proteins in biotechnology

Measuring air pressure in meteorology

Determining acidity in chemistry

What does HPLC primarily stand for?

High-Performance Liquid Chromatography

High-Purity Liquid Chromatography

High-Precision Liquid Chromatography

High-Pressure Liquid Chromatography

What is the primary difference in how the mobile phase moves in paper chromatography versus HPLC?

In paper chromatography, it moves by capillary action, while in HPLC, it's forced by high-pressure pumps.

In both, the mobile phase moves by capillary action.

In both, the mobile phase is forced through by high-pressure pumps.

In paper chromatography, it's forced by high-pressure pumps, while in HPLC, it moves by capillary action.

In HPLC, what does a drop in the detector reading indicate?

A component that absorbs UV light is eluting from the column.

The column is becoming clogged.

The sample injection was unsuccessful.

How do different components of a mixture separate in chromatography?

Based on their relative affinity for the mobile and stationary phases.

Based on their density differences.

Based on their molecular weight.

What is the main advantage of HPLC over GLC for temperature sensitive samples?

HPLC operates at lower temperatures

HPLC cannot separate hydrocarbons

A mixture of organic compounds was analysed using high-performance liquid chromatography (HPLC) and produced the result shown in the diagram to the left. Which one of the following statements is incorrect?

Butanol has the weakest attraction to the stationary phase.

Ethanoic acid has the strongest attraction to the mobile phase.

In the sample analysed, butanol was in the highest concentration.

Using a higher pressure would result in all retentions times being shorter.

both qualitative and quantitative analyses

neither qualitative nor quantitative analyses

Which of the following is NOT a use of High Performance Liquid Chromatography (HPLC)?

Measuring the melting point of solids

Testing pharmaceutical products

Quality control of herbicides and insecticides

Analysis of alcoholic beverages

Which characteristic is essential for the non-volatile liquid used as the stationary phase in gas-liquid chromatography?

It must be stable and non-volatile.

It must be highly volatile to evaporate quickly.

It needs to be chemically reactive with the sample.

It should be a solid support material only.

How are different substances in a sample mixture separated in gas-liquid chromatography?

By their differing solubilities in the liquid coating of the stationary phase.

By their differing boiling points in the oven.

By their differing molecular masses in the carrier gas.

By their differing affinities for the polymer tube.

What does the area under a peak in a chromatogram indicate?

The concentration or amount of the substance.

The retention time of the substance.

The molecular mass of the substance.

The volatility of the substance.

Which of the following statements about the mobile phase in Gas-Liquid Chromatography (GLC) are correct?

It is usually an inert gas such as nitrogen, helium, or argon.

It interacts with the stationary phase to separate components.

It is responsible for carrying the sample through the column.

Which of the following is NOT a use of Gas-Liquid Chromatography (GLC)?

Measure the boiling point of water

Monitor pollutants in air and other gas samples

Analyse foods for fatty acid content and food colouring

Topic 15 Part 8: Chromatography- Independent Learning Task Lesson

78 questions

Show all answers

1.

SLIDE QUESTION

30 sec • Ungraded

2.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

Why is chromatography considered an important technique in organic chemistry?

Because it helps separate components of a mixture for further analysis

Because it is used to measure temperature changes in reactions

Because it is the only method to identify organic compounds

Because it is primarily used for synthesizing new compounds

3.

SLIDE QUESTION

30 sec • Ungraded

4.

SLIDE QUESTION

30 sec • Ungraded

5.

MULTIPLE CHOICE QUESTION

1 min • 1 pt

Which of the following best describes the difference between the mobile phase and the stationary phase in chromatography?

The mobile phase is always a liquid or gas, while the stationary phase is always a solid or a liquid on a solid support.

The mobile phase is always a solid, while the stationary phase is always a liquid.

Both phases are always liquids.

Both phases are always gases.

6.

SLIDE QUESTION

30 sec • Ungraded

7.

SLIDE QUESTION

30 sec • Ungraded

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