Chemical analysis

A student investigated the colours in three different flowers, A, B and C, using paper chromatography. The colours are soluble in ethanol but are insoluble in water. This is the method used. 1. Place ethanol in a beaker. 2. Add the flower. 3. Stir until the colours dissolve in the ethanol. 4. Filter the mixture. 5. Put spots of the coloured filtrate on the chromatography paper. The filtrate was a very pale coloured solution. How could the student obtain a darker coloured solution? Select two options.

Figure 2 shows the apparatus used. What two mistakes did the student make in setting up the apparatus? Select two options.

Another student sets up the apparatus correctly. Figure 3 represents the student's results. What two conclusions can be made from Figure 3? Select two options.

The student records some measurements. - the colour from flower B moves 7.2 cm - the solvent moves 9.0 cm Calculate the R₟ value for the colour from flower B. Use the equation: R₟ = distance moved by colour / distance moved by solvent

The student tests the gas produced by bubbling it through limewater. No change is seen in the limewater. Give one conclusion the student can make about the gas.

The student tests the gas produced using a burning splint. Name the gas the student is testing for. Give the result of a positive test for this gas.

This question is about chemicals in fireworks. Coloured flames are produced because of the metal ions in the fireworks. What colour flame would sodium ions produce?

Name a metal ion that would produce a green flame.

Some fireworks contain a mixture of metal ions. Why is it difficult to identify the metal ions from the colour of the flame?

Flame emission spectroscopy is used to identify metal ions in a firework. Figure 8 shows the flame emission spectra of five individual metal ions and a spectrum for a mixture of two metal ions. Which two metal ions are in the mixture? Select two options.

The compounds in fireworks also contain non-metal ions. A scientist tests a solution of the chemicals used in a firework. Silver nitrate solution and dilute nitric acid are added to the solution. A cream precipitate forms. Which ion is shown to be present by the cream precipitate?

Describe a test to show the presence of sulfate ions in the solution. Give the result of the test if there are sulfate ions in the solution.

Methylated spirit is a useful product made from a mixture of substances. Table 6 shows the mass of the substances in a sample of methylated spirit. What name is given to a useful product such as methylated spirit?

A student investigated an aqueous solution of a salt. The student identified that the salt solution contained only sodium ions and chloride ions. Describe a test to identify sodium ions. Give the result of the test.

Describe a test to identify chloride ions. Give the result of the test.

Nitric acid is produced by reacting ammonia with oxygen. The word equation is: ammonia + oxygen → water + nitric acid Platinum is a catalyst in this reaction. Describe the test for oxygen gas. Give the result if oxygen gas is present.

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.

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 Rₑ 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 Rₑ 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 sulfuric acid. Sulfuric acid contains sulfate ions. Describe the test for the presence of sulfate ions in sulfuric acid. Give the result of the test.