Chromatography

This question is about chromatography.

Figure 4 shows some equipment used for paper chromatography.

Complete Figure 4 to show how the equipment can be used to separate the dyes in an ink.

You should draw and label:

a piece of chromatography paper in the beaker

a start line on the chromatography paper

a spot of the ink on the chromatography paper at the start of the experiment.

Why should a pencil be used to draw the start line on the chromatography paper?

The R_f value of a dye was 0.80

A spot of the dye moved a distance of 5.2 cm.

Calculate the distance moved by the solvent.

Use the equation:

distance moved by spot R = distance moved by solvent

How is the distance moved by the spot of the dye measured?

Tick () one box.

Which two changes could produce a different R_f value for this dye?

Tick () two boxes.

A different dye is a pure substance.

How many spots will this dye produce during chromatography?

Which is an advantage of using gas chromatography instead of paper chromatography?

Choose the answer from the box.

less sensitive more accurate slower

Gas chromatography is.

This question is about paper chromatography.

A student investigated substance Y using paper chromatography.

This is the method used.

1. Draw a start line in ink on a piece of chromatography paper.

2. Put spots of four different dyes, A, B, C and D, and a spot of substance Y on the start line.

3. Dip the paper into water so that the water level is below the start line.

4. Wait until the water has risen to near the top of the paper.

The student’s method contains a mistake in Step 1.

What is the mistake in Step 1 ?

Give one reason for your answer.

A different student used a method which gave valid results.

Figure 4 shows the results.

How many different dyes are in substance Y ?

Use Figure 4.

Which of the four dyes, A, B, C and D, could be in substance Y ?

Give one reason for your answer.

Use Figure 4.

Suggest why dye D remained on the start line at the end of the investigation.

Use Figure 4.

The student determined that:

the distance moved by the water was 6.0 cm

the distance moved by dye A was 2.4 cm.

Calculate the R_f value of dye A.

Use the equation:

distance moved by dye A R distance moved by water

Complete the sentence.

Choose the answer from the box.

A student investigated an orange dye (A) using paper chromatography.

Figure 4 shows the results of Experiment 1 and Experiment 2 using orange dye A.

Explain why the yellow dye and red dye travel different distances in Experiment 1.

Refer to forces of attraction between the dyes and the chromatography paper in your answer.

The student used the same type of chromatography paper in Experiment 1 and in Experiment 2.

Explain why the yellow dye is in different positions in Experiment 1 and in Experiment 2.

Use Figure 4.

Figure 4 is repeated below.

Figure 4 shows the results of Experiment 1 and Experiment 2 using orange dye A.

The student investigated a different orange dye (B).

Figure 5 shows the results of Experiment 3 using orange dye B.

Compare the purity of the orange dyes A and B.

Give reasons for your answer.

Use Figure 4 and Figure 5.

The student calculated that the R_f value of the orange dye in the experiment shown in Figure 5 was 0.48

Calculate the distance moved by the solvent front when the orange dye had moved 5.4 cm.

Why is the R_f value of a dye not affected by how far the solvent front is allowed to travel?

Another type of chromatography is called gas chromatography.

Gas chromatography is an instrumental method of chemical analysis.

Scientists tested the orange dyes using gas chromatography.

Suggest two advantages of using the instrumental method of gas chromatography rather than paper chromatography.

This question is about chromatography.

A student investigated an orange dye using paper chromatography.

Figure 3 shows the apparatus at the start of the investigation.

Complete the labels on Figure 3.

Figure 4 shows the results at the end of the investigation.

The student made a mistake in the investigation.

What mistake did the student make to produce the results shown in Figure 4 ?

Tick (✓) one box.

A different student did the investigation correctly.

Figure 5 shows the results.

How do the results in Figure 5 show that the orange dye is not a pure substance?

Determine the R_f value for the red spot.

You should measure:

• the distance moved by the red spot

• the distance moved by the solvent.

Use Figure 5 and the equation:

distance moved by red spot R = distance moved by solvent

Which spot had the greatest R_f value?

Use Figure 5.

Tick (✓) one box.

This question is about chromatography.

A student investigated an orange food colouring using two different types of chromatography paper. The food colouring:

• contained a mixture of red and yellow dyes

• was soluble in water.

This is the method used.

1. Draw a start line on a piece of type A chromatography paper.

2. Put a spot of orange food colouring on the line.

3. Put the paper into a beaker containing water as a solvent.

4. Wait for the water to travel up the paper.

5. Measure the distance above the start line moved by the red and yellow dyes and the water.

6. Repeat steps 1 to 5 using type B chromatography paper.

Figure 3 shows how the student set up the apparatus.

The student made two mistakes when setting up the apparatus. Give two mistakes the student made.

Another student set up the apparatus correctly. Table 3 shows the results.

Determine value X in Table 3.

Changing the type of chromatography paper resulted in different R_f values for the red dye.

Explain why the R_f values for the red dye are different using the two types of chromatography paper. Use Table 3.

What other change to the investigation could result in a different R_f value for the red dye?

This question is about ethanol.

The formula of ethanol is C₂H₅OH Complete the displayed structural formula of ethanol.

Which is one use of ethanol? Tick (✓) one box.

Ethanol is used as a solvent in some inks. A student used paper chromatography to show that an ink contained two different dyes. Figure 4 shows the apparatus at the end of the investigation.

Describe a method the student could have used for the investigation.

Ethanol can be produced from sugar solution by fermentation. What must be added to sugar solution to produce ethanol?

E5 and E10 are types of fuel used in cars. These fuels contain ethanol and petrol. Table 6 shows information about E5 and E10.

Calculate the mass of ethanol in 4.4 kg of E5. Give your answer in grams. Use Table 6.

The ethanol in E5 and E10 is produced from sugar. Sugar is produced from plants. Explain why the production of E10 removes more carbon dioxide from the atmosphere than the production of E5. Use Table 6.

Table 7 shows the energy content of ethanol and petrol.

Suggest one disadvantage of using E10 instead of E5. Complete the sentence. A disadvantage of using E10 is that

This question is about paper chromatography.

A food colouring contains a dye.

Plan an investigation to determine the R_f value for the dye in this food colouring.

Your plan should include the use of:

• a beaker

• a solvent

• chromatography paper.

Two students investigated a dye in a food colouring using paper chromatography.

Each student did the investigation differently.

The R_f values they determined for the same dye were different.

How did the students’ investigations differ?

Tick (✓) one box.

Paper chromatography involves a stationary phase.

What is the stationary phase in paper chromatography?

Tick (✓) one box.

This question is about paper chromatography. A food colouring contains a dye.

Plan an investigation to determine the R_f value for the dye in this food colouring.

Your plan should include the use of:

• a beaker

• a solvent

• chromatography paper.

Two students investigated a dye in a food colouring using paper chromatography. Each student did the investigation differently. The R_f values they determined for the same dye were different. How did the students’ investigations differ? Tick (✓) one box.

Paper chromatography involves a stationary phase. What is the stationary phase in paper chromatography? Tick (✓) one box.

This question is about ink.

A student investigated green ink using paper chromatography in a beaker.

Figure 6 shows:

• the results the student obtained

• measurements A, B, C and D the student could make.

Figure 6

The student calculated the R_f value of the blue dye.

The student measured:

• the distance moved by the blue dye = 2.7 cm

• the distance moved by the solvent = 9.0 cm

Calculate the R_f value of the blue dye.

Use the equation:

Which measurements on Figure 6 are needed to calculate the R_f value of the yellow dye?

Tick (✓) one box.

Paper chromatography has a stationary phase and a mobile phase.

Draw one line from each phase to the identity of that phase in the student’s investigation.

Phase Identity

The green ink contains 85% yellow dye and 15% blue dye.

Determine the simplest whole number ratio of yellow dye: blue dye in the green ink.

Which word correctly describes the green ink?

Tick (✓) one box.

The student repeated the investigation using green ink containing 75% yellow dye and 25% blue dye.

What would happen to the R_f value of the yellow dye?

Tick (✓) one box.

This question is about ink. A student investigated green ink using paper chromatography in a beaker. The student used water as the solvent.

Figure 2 shows the chromatogram obtained.

Figure 2

The R_f value of the yellow dye = 0.60 The distance moved by the yellow dye = 5.7 cm Calculate the distance moved by the solvent.

The green ink contains more than two compounds. Suggest one reason why only two spots are seen on Figure 2.

On the student’s chromatogram, the yellow and blue spots are very close together. Which two ways could increase the distance between the spots? Tick (✓) two boxes.

The manufacturers of the green ink always use the same proportions of yellow dye and blue dye. Suggest one reason why.

The R_f value of a dye depends on:

• the solubility of the dye in the solvent

• the attraction of the dye to the paper.

Which will definitely produce a smaller R_f value if the solvent and paper are both changed? Tick (✓) one box.

The dye is more soluble in the new solvent and more attracted to the new paper. 8

A student investigated the colours in three different flowers, A, B and C. The colours are soluble in ethanol but are insoluble in water. This is the method used.

1. Crush flower A.

2. Add ethanol to flower A.

3. Filter the mixture.

4. Put spots of the coloured filtrate on to the chromatography paper.

5. Repeat steps 1-4 with flowers B and C.

Figure 4 shows the apparatus used.

The student made two mistakes in setting up the apparatus. Give one problem caused by each mistake.

Another student set up the apparatus correctly. Figure 5 represents the student’s results.

Give two conclusions you can make from Figure 5.

Colour A has an R_f value of 0.65 Colour A moves 3.2 cm

Calculate the distance moved by the solvent.