OCR GCSE Chemistry B (21st Century) Paper 4 June 2022 question paper

Petrol contains cyclo-octane.

Which symbol should be used to warn people of the main hazard when handling cyclo-octane?

Tick (✓) one box.

Write down two safety precautions people should take when filling their cars with petrol.

Carbon makes a much bigger range of different types of molecules than any other element.

Give one reason why carbon atoms can form so many different types of molecules.

Use Fig. 1.1 to help you to answer.

Explain why polyethene and synthetic rubber have different properties.

Use ideas about structure from Fig. 1.1 to help you to answer.

How are nanoparticles different to the other substances in Fig. 1.1 ?

Explain why the structure of carbon nanoparticles helps them to carry medicine molecules into the body.

Ammonia is used to make fertilisers. It is produced in a large-scale process.

The equation shows the reaction that happens in the process:

The process happens in a reactor.

The percentage yield of ammonia is usually between 10% and 20%.

Use the equation to explain why it is not possible to get 100% yield of ammonia.

The gas that leaves the reactor contains ammonia mixed with two other gases.

Use the equation to help you to give the names of the other two gases.

An ammonia factory tests a new reactor.

The table shows the theoretical yield and actual yield for a process in the new reactor.

Calculate the percentage yield for the process in the new reactor.

Ammonia is very soluble in water.

Kofi does an experiment to make some ammonia.

He tries to collect it using the apparatus shown.

Bubbles of ammonia gas enter the water but no gas collects in the test-tube.

What happens to the ammonia gas when it enters the water?

Ammonia is an alkaline gas.

The pH of ammonia solution can be measured using a pH meter.

Predict the pH of ammonia.

Describe another method you could use to measure the pH of ammonia solution.

The graph shows the change in carbon dioxide concentration in the Earth’s atmosphere over the last 575 million years.

How many millions of years ago was the concentration of carbon dioxide at its highest point?

........ million years ago

What was the concentration of carbon dioxide at its highest point?

........ ppm (parts per million)

Scientists say that the concentration of carbon dioxide is now 0.04 %.

In the year 2000 the concentration of carbon dioxide was 370 ppm (parts per million).

Do a calculation to find out the difference between these two values.

Give your answer in ppm.

Use this formula:

concentration in ppm = concentration in % × 10⁴

difference between values........ ppm

Some scientists fear that increased carbon dioxide in the air may lead to global food shortages.

Explain why this could happen.

The table shows information about some alkanes.

The empirical formula of octane is C₄H₉.

What is the empirical formula of pentacontane?

The empirical formulae of methane and propane are the same as their molecular formulae.

Explain why.

Predict the boiling point of octane.

Explain your reasoning.

Boiling point........ °C

* A text book has this description of a homologous series.

A homologous series contains compounds with similar structures, the same general formula and similar chemical properties. The compounds show a trend in physical properties down the series.

Use your own knowledge and the information in the table to explain how the alkanes match this description of a homologous series.

Some metals are extracted from their ores by heating with carbon.

Other metals are extracted from their ores by electrolysis.

Fig. 5.1 shows the order of reactivity of some metals, compared to carbon.

Explain why calcium and copper must be extracted by different methods.

What are the most common methods of extraction for iron, potassium, aluminium and lead from their ores?

Use ideas about the order of reactivity of the metals to help you to answer.

Put a tick (✓) in one box in each row.

Some copper ores contain copper sulfide.

Copper is extracted from copper sulfide in a two-stage process.

Stage 1: Copper sulfide reacts with oxygen:

Stage 2: Copper oxide reacts with carbon:

Look at the equation for Stage 1.

Predict whether the mass of the solid increases, decreases or stays the same during Stage 1.

Use the Periodic Table and calculations of relative formula masses to help you.

During Stage 2, the total mass of the solids decreases.

Explain why Stage 2 obeys the law of conservation of mass even though the total mass of the solids decreases.

The reaction of copper in Stage 2 can be represented by a half equation:

Is copper oxidised or reduced in this half equation?

Explain your answer.

Oxidised or reduced?........

Neon is a gas in Group 18 (0) of the Periodic Table.

Use the particle model in Fig. 6.1 to describe what happens to the arrangement and movement of the atoms when neon changes from a liquid to a gas.

Sodium atoms form sodium ions with a single positive charge.

Neon atoms do not form ions.

Use ideas about electrons to explain these statements.

Jane does an experiment.

She puts 10 cm³ of copper sulfate solution in a boiling tube. She adds 5 cm³ of sodium hydroxide solution. A precipitate of copper hydroxide forms.

Complete the word and symbol equations for the reaction in the boiling tube by filling in the name of the missing product and the state symbols for each substance.

The final mixture contains a precipitate of copper hydroxide mixed with a solution of other dissolved substances.

Jane wants to separate pure copper hydroxide from this mixture. She wants to make sure that she removes any traces of other dissolved substances from the precipitate.

........

........

........

Jane leaves the copper hydroxide to dry in a warm oven. After 30 minutes she weighs the copper hydroxide on a balance.

Jane is not sure if the copper hydroxide is completely dry.

Suggest how Jane can use the oven and the balance to show that the copper hydroxide is completely dry.

Plot Jane’s results on the graph.

Draw lines of best fit to show the pattern in the results.

Volume of sodium hydroxide solution added (cm³)

Suggest why the mass of the dry precipitate does not continue to increase when more than 20 cm³ of sodium hydroxide solution is added.

Before she sets up the cell, Beth tests each gas to check its identity.

Describe the tests and the results for hydrogen and oxygen gas.

hydrogen test........

result........

oxygen test........

result........

These half equations show the reactions that happen at each electrode in the fuel cell:

Beth wants to make sure that she gets the highest possible potential difference from the fuel cell.

She makes sure that she uses double the volume of hydrogen compared to oxygen.

Use the half equations to explain why she needs to do this.

Use the half equations to write an overall equation for the reaction that happens in the fuel cell.

A fuel cell filled with potassium hydroxide solution works better than a fuel cell filled with pure water.

One reason it works better is because potassium hydroxide solution is a better electrical conductor than pure water.

Explain why potassium hydroxide solution is a better electrical conductor than pure water.

Use the equations to suggest one other reason why using potassium hydroxide solution helps the fuel cell to work better.

Beth uses a fixed amount of hydrogen and oxygen gas. After a time the potential difference of the cell decreases.

Explain why this happens.

Beth’s company want to use the cell to provide power for a submarine.

Submarines travel deep under the surface of the sea.

Most submarines have engines that burn diesel fuel.

Beth thinks that submarines that burn diesel fuel produce waste that is much more harmful to the sea than submarines that use hydrogen fuel cells.

Explain why she is correct.

Give one disadvantage of using a hydrogen fuel cell rather than diesel for a submarine.

The graph shows the solubility of some Group 1 salts in water.

Use data from the graph to calculate the solubility of sodium chloride at 50 °C.

Use the information: 100 g of water = 100 cm³ of water.

Give your answer in g / dm³.

Solubility of sodium chloride at 50 °C........ g / dm³

Calculate the concentration of sodium chloride at 50 °C in mol / dm³. (ii)

Use your answer to (a)(i).

Give your answer to 3 significant figures.

Concentration of sodium chloride at 50 °C........ mol / dm³

Kai looks at the graph and writes down a mathematical relationship.

Kai writes:

solubility of potassium chloride temperature

Use the graph to explain in words why this relationship is incorrect.

Use data from the graph to do a calculation to predict the solubility of potassium chloride at 100 °C.

Solubility........ g in 100 g of water