OCR GCSE Chemistry B (21st Century) Paper 4 June 2019 question paper

Alex collects some samples of minerals from a spoil heap near an old mine.

Alex tests two samples of minerals, A and B, to identify the ions that they contain.

He carries out flame tests on each sample and compares his results (Table 1.1) to a reference book of flame colours for some metal ions (Table 1.2).

Use information from Table 1.1 and Table 1.2 to explain why Alex cannot be certain which ions are in the samples.

Alex makes a solution of a sample of each mineral in water and does some further tests.

The tests he carries out, and his results, are shown in Table 1.3.

Alex thinks that mineral A contains two negative ions.

How can you tell from the results that Alex is right?

Identify the ions in mineral A and mineral B.

Choose words from this list.

copper calcium iron zinc carbonate chloride sulfate

Alex also has an emission spectroscopy machine to analyse samples of minerals.

Give one advantage of using an emission spectroscopy machine, rather than flame tests or chemical tests, to identify samples.

Silver nanoparticles are used in some socks to remove the smell of sweaty feet.

Silver nanoparticles have different properties to larger pieces of silver because they have a different surface area to volume ratio.

The diagram shows what happens when a larger cube of silver is cut into eight smaller cubes.

The volume and surface area of a cube can be worked out using these formulae:

volume = l × l × l

surface area = 6 × l × l

Table 2.1 shows the volume, surface area, and surface area to volume ratio for the larger

Complete Table 2.1 by filling in the blank spaces for the eight smaller cubes.

Use this space to show your working.

Use ideas about surface area and volume to explain why nanoparticles of silver have a different surface area to volume ratio than larger silver particles.

New research has shown that nanoparticles may be used to treat cancer. However, some scientists are worried about the negative effects of nanoparticles on the body.

Explain why metal nanoparticles may be able to enter the brain even though metal particles usually cannot.

Use ideas about risk and benefit to evaluate the use of nanoparticles in socks and to treat cancer.

Ali investigates how the pH changes when dilute sodium hydroxide reacts with dilute hydrochloric acid.

He puts 20.0 cm³ of dilute hydrochloric acid in a beaker. He adds dilute sodium hydroxide, 1.0 cm³ at a time, to the acid.

He uses a pH meter to measure the pH after each addition of sodium hydroxide.

Ali plots a graph of his results.

volume of dilute sodium hydroxide added (cm³)

Ali writes an ionic equation for the reaction.

Use the ionic equation and values from the graph to explain the pH changes that happen during the reaction.

Ali started with 20.0 cm³ of dilute hydrochloric acid in the beaker.

Explain how his results show that the acid is more concentrated than the dilute sodium hydroxide.

The repeating unit of some polymers has the structure shown in Fig. 4.1.

What is the name for this type of polymer?

addition polyamide polyamine polyester oxidised

Complete the diagram in Fig. 4.2 by drawing the structure of molecule B.

The polymer was originally made by reacting monomers, molecule A and molecule B together.

How is the reaction to make the polymer different from the reaction in Fig. 4.2 ?

Explain your answer.

Explain why molecule A is called a dicarboxylic acid.

PET is a type of polymer used to make drinks bottles.

PET has the repeating unit shown in Fig. 4.3.

The average relative formula mass of polymer molecules in a sample of PET is 55 000.

How many repeating units does each polymer molecule contain?

Give your answer to the nearest whole number.

Write a symbol equation for the reaction that happens when copper carbonate is heated.

Copper made by the method in Fig. 5.1 contains solid impurities.

Name two solid impurities that the copper may contain.

Jane uses the flowchart in Fig. 5.1 as a method in the laboratory.

Jane’s teacher gives her this equation to help her to work out her theoretical yield of copper.

theoretical yield = 0.51 × mass of copper carbonate at start

Jane uses the equation to work out what mass of copper carbonate she should use to make a theoretical yield of 5.0 g of copper.

Calculate the starting mass of copper carbonate she should use.

Give your answer to 2 significant figures.

When Jane follows her method, she only makes 2.4 g of copper.

Calculate Jane’s percentage yield.

Jane comments on her method.

Suggest what Jane could do to make sure she gets the highest possible percentage yield.

Use the flowchart in Fig. 5.1 to support your answer.

New methods of copper extraction have been developed.

One of these methods uses bacteria to extract copper from the ground around old mines.

Evaluate the effects on the environment of using bacteria to extract copper compared to the method in the flow chart.

Ammonium sulfate is a fertiliser. It is usually sold to farmers as a solid in large sacks.

Different industrial processes can be used to make ammonium sulfate, as shown in Table 6.1

Use information from Table 6.1 to answer these questions.

Both process 1 and process 2 are exothermic.

Explain why an exothermic reaction has a positive effect on how each process works.

Process 1 and process 3 both need to go through further separation after the main reactions.

How can pure, solid ammonium sulfate be separated from the reaction mixtures in process 1 and process 3 ?

Process 1........

Process 3........

Use relative formula masses to calculate the atom economy of process 3.

Give your answer to 1 decimal place.

The sustainability of each process in Table 6.1 is different.

Explain what sustainability means.

Give two examples from Table 6.1 to explain why some processes are more sustainable than others.

Process 3 can be carried out as a batch process in the laboratory.

In industry, process 3 is carried out as a continuous process.

Explain why batch processes are more suitable for use in the laboratory, but continuous processes are more suitable for industry.

7* Li is planning a presentation on sodium chloride.

She looks for a diagram to show the bonding, structure, movement and arrangement of particles in solid sodium chloride.

She finds these diagrams.

Discuss the advantages and disadvantages of using each diagram to represent solid sodium chloride and outline the features that an ideal diagram should have.

The table shows information about some transition elements.

Which two statements about the melting points are true?

Tick (✓) two boxes.

Mercury and zinc are not typical transition metals.

Use information from the table to explain why.

Copper can form two oxides with different formulae. In both formulae, the oxide ion is O^2–

Write the formulae for the two oxides.

Use information from the table to help you.

Chromium also forms an oxyanion with the formula CrO₄^2–.

Suggest why this ion is known as an oxyanion.

Which statement describes another correct property for transition metals?

Tick (✓) one box.

Over the last 20 years there have been a series of agreements between governments to limit the emission of greenhouse gases. These gases include carbon dioxide, methane and nitrous oxides.

Governments are more concerned about reducing the emissions of carbon dioxide than reducing the emissions of the other gases.

The table shows some measurements of the concentrations of these gases in the atmosphere

Calculate the percentage of methane in the atmosphere.

1.0 ppb = 1.0 × 10^–7%

Use your answer to (a)(i) to explain why governments are more concerned about carbon dioxide emissions than emissions of the other gases in the table.