OCR GCSE Chemistry B (21st Century) Paper 4 November 2021 question paper

Lithium (Li), sodium (Na) and potassium (K) are in Group 1 of the Periodic Table.

How does the atomic radius change down Group 1? Use the graph.

Give the symbols of the two elements which have the smallest atoms. Use the graph.

Which group of the Periodic Table do the elements in (b)(i) belong to? Use the Data Sheet.

Which statements in the table are true and which are false ?

Tick one box (✓) in each row.

Kai makes a scale model of a lithium (Li) atom.

The diagram shows the radius of his model of a lithium atom.

Model of a lithium (Li) atom

Kai makes a model of a sodium (Na) atom to the same scale.

Calculate the radius of the sodium atom model, in cm.

Use the graph.

Kai makes his lithium model red to match the flame test colour of lithium.

What colour should he make his sodium model?

Kai designs a sign to tell people about the particles inside a sodium atom.

Complete the missing information on the sign.

More information about the particles

Hydrogen peroxide is a waste product produced by cells in our bodies. Hydrogen peroxide is broken down by an enzyme to form water and oxygen.

Beth adds a small amount of an enzyme to some hydrogen peroxide. She collects the oxygen given off in a gas syringe. She records the total volume of oxygen every minute.

The graph shows her results.

Use the graph to help you answer (a).

How long does it take for the reaction to finish?

How much oxygen is given off by the end of the reaction?

Calculate the average volume of oxygen given off per second.

........ cm³ / s

The reaction that breaks down hydrogen peroxide does not start until the enzyme is added. When the enzyme is added, oxygen is given off quickly.

Explain this statement.

Use ideas about rates of reaction in your answer.

Some brands of tablets that treat stomach upsets contain calcium carbonate, CaCO₃.

Jane does experiments to measure the mass of calcium carbonate in each tablet for two different brands of tablets.

Jane wants to make sure that the samples she tests are representative of all the tablets in each brand.

Why is it important to make sure that the samples are representative ?

What should Jane do to make sure her choice of tablets is representative?

Tick (✓) two boxes.

Jane reacts dilute hydrochloric acid with a tablet. The equation shows the reaction that happens:

Which two statements explain why this reaction is a neutralisation reaction?

Tick (✓) two boxes.

Jane thinks her results are inaccurate because the tablets contain other ingredients. The labels show the other ingredient in each brand of tablet.

Explain how each of the other ingredients will affect the volume of acid needed to neutralise each tablet.

Citric acid........

Magnesium hydroxide........

Layla heats a small piece of sodium. She then puts it in a jar of chlorine gas, as shown:

The sodium burns with a bright flame. A white solid is formed.

She repeats the experiment using different Group 1 and Group 7 elements. She uses jars containing group 7 gases.

Complete the table of information about the reactions between Group 1 and Group 7 elements.

Which of the reactions from the table do you expect to be the fastest?

Explain your choice.

Reaction between........ and........

Layla tests some of the salts formed in the reactions. She collects samples of solid sodium chloride and solid sodium bromide.

She uses silver nitrate solution to test the salts, to show that they contain chloride and bromide ions.

Describe the steps she should follow to test each salt and state what results she should expect.

Table 5.1 and Table 5.2 show information about the structures and uses of diamond and graphene.

* Discuss the similarities and differences between the properties of diamond and graphene in terms of their structures and explain why they have different uses.

Use information from Table 5.1 and Table 5.2 in your answer.

New types of batteries that contain nanoparticles of graphene have been available for less than 10 years.

Some people are concerned about the health effects of using new products that contain nanoparticles.

Why are people concerned about the health effects of nanoparticles?

Life cycle assessments are done to evaluate the sustainability of making new products.

Suggest two factors that are important to consider in evaluating the sustainability of graphene batteries.

Some diesel cars have a system which uses a solution of urea, (NH₂)₂CO, to remove nitrogen oxides from their exhaust gases.

Urea solution reacts in a two stage process.

Stage 1: At temperatures above 100 C, urea solution breaks down to make ammonia.

Stage 2: Ammonia then reacts with nitrogen oxide.

The overall reaction that happens in Stage 1 and Stage 2 produces three waste gases which leave the exhaust.

Name these three gases.

The urea solution is sprayed into the hot exhaust gases before they leave the car.

Explain why the two equations show the state symbol for water as (g) rather than (l).

In the car, the urea solution is stored in a tank. The tank is kept cool by being kept far away from the hot engine.

Why is it important to keep the urea solution cool?

A redox reaction happens when oxidation and reduction happen in the same equation.

Explain why the reaction in Stage 2 is a redox reaction.

Amir draws the displayed formulae of some of the substances involved in the reactions.

Amir says that the number of bonds formed by each element can be calculated by using this equation:

Number of bonds formed = (18 – x)

where x = group number of the element shown on the Periodic Table.

Show that this equation works for the number of bonds formed by nitrogen and oxygen.

Suggest one reason why this equation cannot be used for hydrogen.

Urea, (NH₂)₂CO, contains one double bond.

Draw the displayed formula of urea.

Kareem investigates the order of reactivity of five metals, aluminium, magnesium, calcium, copper and zinc. He does two experiments, as shown.

In experiment 1 he puts small pieces of each of the metals into water. He observes the metals over five minutes.

In experiment 2 he puts small pieces of each metal into dilute acid. He measures the time taken to collect 10 cm³ of gas.

Table 7.1 and Table 7.2 show Kareem’s results.

* Explain what conclusions can be made about the reactivity of the five metals from Kareem’s experiment.

Include any uncertainties in your conclusions.

Use information from Table 7.1 and Table 7.2 to support your answer.

Which two statements explain why some metals are more reactive than others?

Tick (✓) two boxes.

Aluminium is extracted from aluminium oxide by electrolysis.

The diagram shows the tank used to electrolyse aluminium oxide.

Before electrolysis, solid aluminium oxide is dissolved in a hot, molten compound called cryolite. The formula for cryolite is Na₃Al F₆.

Explain why the formula for cryolite contains six fluoride ions.

Use ideas about charges in your answer.

The hot cryolite dissolves the aluminium oxide to form a molten solution.

Explain why solid aluminium oxide has to be made into a molten solution before electrolysis.

Describe what happens at each electrode during the electrolysis.

The melting point of aluminium metal is 660 C.

What temperature should the inside of the tank be to make sure that aluminium leaves the tank as a liquid?

The table shows the hydrogen ion concentration and the pH for different concentrations of dilute acids.

Which acid in the table shows the highest concentration of hydrogen ions in solution?

Tick (✓) one box.

Sundip writes this relationship:

What does Sundip’s relationship mean?

Do you agree with Sundip’s relationship?

Use data from the table to support your answer.

Explain why the same concentration of hydrochloric acid and sulfuric acid have different concentrations of hydrogen ions and different pH values.