Chromatography

Q consists of a pure sample of a substance with one $R_f$ value of $0.9$. In the chromatogram shown, which letter corresponds to Q?

May/June 2016

Chromatography may be used to separate the dyes in black ink.

May/June 2016

Four samples are placed as spots on chromatography paper. It is known that one of these samples is pure compound Q. A separate spot of pure compound Q is also put onto the paper. The paper is then put into a solvent. The diagram shows the chromatogram obtained. Which statement is correct?

May/June 2017

A molecule is made up of four amino acid units joined in the same way as in a protein. After hydrolysis, the colourless solution obtained is placed as a spot on chromatography paper. The paper is then put into a suitable solvent. The diagram shows the completed chromatogram.

May/June 2018

A paper chromatography experiment is used to separate and identify the mixture of amino acids formed when a protein is hydrolysed. Which apparatus is required?

May/June 2019

The diagram shows a chromatogram of the colourless acids found in a drink. The chromatogram has been treated with a locating agent. A table of $R_f$ values for the possible acids is given. Which acids are present in the drink?

May/June 2019

E150a and E155 are both brown food colourings. Devise an investigation to determine whether the brown food colouring in a soft drink is E150a or E155. Both food colourings dissolve in water. You are given solutions of E150a, E155 and the brown food colouring from the soft drink. You also have access to the apparatus usually available in a chemistry laboratory. You should include a labelled diagram with your plan and add the key practical details.

May/June 2019

A paper chromatography investigation is carried out to determine an $R_f$ value for $\text{Fe}^{3+}(aq)$. The chromatogram is shown. To make the spot that contains $\text{Fe}^{3+}(aq)$ easier to see, the paper is sprayed with aqueous sodium hydroxide so that iron(III) hydroxide precipitate is produced. In the chromatogram, the $R_f$ of $\text{Fe}^{3+}(aq)$ is shown by ......1...... and the colour of the precipitate is ......2...... . Which row gives the correct answers for gaps 1 and 2?

May/June 2023

The outcomes from a paper chromatography experiment are displayed. X is an aqueous solution containing a salt of a Group I element. Y is an aqueous solution containing a salt of a transition element. Which row is correct?

May/June 2023

A student is using chromatography to separate the dyes in a food colouring. Fig. 1.1 shows the apparatus that the student uses.

May/June 2023

The chromatogram illustrated has been obtained by placing a spot of black ink at point X. Spot M comes from a blue dye in the ink. What is the $R_f$ value of this blue dye?

May/June 2024

Four samples are tested by paper chromatography. P, Q and R are pure substances. M is a mixture of several different substances. Which substances are present in mixture M?

May/June 2025

In a paper chromatography experiment, an $R_f$ value is determined for $\text{Fe}^{3+}(aq)$. The outcome is shown. To make the spot containing $\text{Fe}^{3+}(aq)$ easier to see, the paper is sprayed with aqueous sodium hydroxide, causing a precipitate of iron(III) hydroxide to form. For the conditions used in the experiment, the $R_f$ of $\text{Fe}^{3+}(aq)$ is ______ and the colour of the precipitate is ______. Which row correctly fills gaps 1 and 2?

Oct/Nov 2016

The chromatogram displays the chromatography results for mixture $Z$, alongside the separate dyes marked $1$, $2$, $3$ and $4$.

Oct/Nov 2016

A chemist wants to separate and identify a mixture of substances by using paper chromatography. The diagram shows the apparatus used. The solvent is water. The chemist leaves the solvent front to reach the top of the paper before removing the paper from the solvent. What problem does this lead to?

Oct/Nov 2017

Ethanol acts as a reducing agent. If it is warmed with acidified aqueous potassium manganate(VII), it can be oxidised. It also evaporates readily at room temperature. As a solvent, it can be used to separate the dyes found in ink. A student uses the apparatus illustrated to perform the separation. The diagram contains errors.

Oct/Nov 2017

The outcome of a paper chromatography experiment is shown below. X is an aqueous solution of a salt of a Group I element. Y is an aqueous solution of a salt of a transition element. Which row is correct?

Oct/Nov 2018

Certain substances can be separated by means of paper chromatography. The diagram illustrates the outcome of running two mixtures in an appropriate solvent. Which spot has an $R_f$ value of $0.37$?

Oct/Nov 2020

Chromatography may be used to separate and identify the dyes in a mixture. Which statement is correct?

Oct/Nov 2020

A student wants to identify the dyes in a dye mixture by separating them. The apparatus used by the student is shown below. The student also tests dyes A, B, C and D.

Oct/Nov 2020

A mixture containing four coloured dyes is examined using chromatography. The outcome is shown. Which alteration will make it possible to see the four dyes?

Oct/Nov 2021

The diagram displays a chromatogram. Which spot has an $R_f$ value of $0.75$?

Oct/Nov 2023

A mixture containing four coloured dyes is tested by chromatography. The outcome is shown. Which alteration would make it possible to view the four coloured dyes separately?

Oct/Nov 2024

The chromatogram for mixture X and the pure substances P, Q, R and S is shown. Which of the following statements is correct?

Oct/Nov 2025