OCR GCSE Chemistry B (21st Century) Paper 3 June 2019 question paper

Diamond and graphite are two forms of carbon.

Fig. 1.1 shows the structure of diamond:

Explain why diamond has a high melting point.

Fig. 1.2 shows the structure of graphite.

Graphite also has a high melting point.

Describe and explain two other properties of graphite.

Use the structure shown in Fig. 1.2 to help explain your answers.

Diamond has a high density.

1.0 g of diamond has a volume of 0.29 cm³.

Calculate the mass of 1.0 cm³ of diamond.

Give your answer to 2 significant figures.

12 g of diamond produces 44 g of CO₂ when it is burned completely.

Jane makes some statements about graphite and diamond:

1 ‘Complete combustion of 12 g of graphite produces less than 44 g of CO₂.’

2 ‘This is because atoms in graphite are further apart than in diamond.’

Do you agree with Jane’s statements?

Explain your answer.

Ben uses chromatography to investigate a solid black food dye.

Ben tests the solubility of the dye in three solvents.

Here are his results:

Which of the three solvents are non-aqueous?

Ben uses paper chromatography to investigate the dye.

Which of the three solvents should Ben use in his investigation?

Here is some information about the experiment:

chromatogram at the start
chromatogram at the end

Name the stationary phase.

What is wrong with the way Ben set up his experiment?

Explain your answer.

Which spot has the greatest R_f value in the chromatogram at the end?

Explain your answer.

Ben thinks the dye is a pure substance. Kareem, another student, disagrees.

Who do you agree with?

Explain your answer.

Ben measures the melting point of the dye.

Describe what Ben would see if the dye is pure.

3 ‘Camping gas’ contains butane.

This is a ‘ball and stick’ model of a butane molecule:

Butane is a hydrocarbon.

Draw a ‘dot and cross’ diagram for a butane molecule.

Chemists use ‘ball and stick’ models and ‘dot and cross’ diagrams.

Give one advantage of using each model.

‘ball and stick’

‘dot-and cross’

The molecular formula of butane is C₄H₁₀.

Calculate the percentage of carbon by mass in butane.

Give your answer to 2 significant figures.

Propane is another hydrocarbon.

Butane, C₄H₁₀, boils at 0 °C.

Propane, C₃H₈, boils at −42 °C.

Explain this difference in boiling point.

Use ideas about intermolecular forces in your answer.

This question is about the efficiency of LED light-bulbs in 2015 compared to 2011.

The table shows part of a life-cycle assessment for the two light-bulbs. The numbers in the table compare the energy used to give the same amount of light in a certain time.

In total, 2015 LED lights use less energy than 2011 LED lights.

Calculate the percentage decrease in energy use at ‘manufacture’ stage from 2011 to 2015.

Give your answer to 2 significant figures.

The data in the table does not cover the whole life-cycle assessment.

Describe in detail the final stage of the life-cycle assessment.

Mendeleev left gaps when he constructed his Periodic Table. He thought elements would be discovered to fill these gaps.

Mendeleev left a gap below aluminium.

Later gallium was discovered and fitted this gap.

Give two reasons why gallium fitted this gap.

Gallium forms an oxide, Ga₂O₃.

Draw a ‘dot and cross’ diagram for the ions in Ga₂O₃.

Show outer electron shells only.

Some cars use hydrogen fuel cells instead of petrol.

This is the reaction that happens in the hydrogen fuel cell:

Suggest one advantage and one disadvantage of using fuel cells instead of petrol.

Advantage

Disadvantage

Complete a reaction profile for the above reaction of hydrogen with oxygen.

On the profile, show:

• the formulae of reactants and products

• the activation energy.

Burning 10 g of hydrogen gives out 1200 kJ of energy.

How much energy is given out when 1.0 mole of H₂ burns?

This question is about Rutherford’s model of the atom.

Rutherford’s model describes:

• a small positive nucleus

• the nucleus surrounded by empty space

• electrons orbiting in this empty space.

Thomson’s ‘plum pudding’ atom was an earlier model of the atom.

Describe one way in which Thomson’s model of the atom was different from Rutherford’s.

A nut has an average diameter of 2 cm.

The diameter of an atom is on average 50 000 times bigger than the diameter of its nucleus.

Estimate the diameter of the nucleus if the atom is as big as the nut.

Give your answer in metres and in standard form.

Sundip reacts zinc with dilute sulfuric acid.

This is the equation for the reaction:

Sundip drops a piece of zinc into some dilute sulfuric acid.

She then drops some zinc powder into the dilute sulfuric acid.

Which reaction is faster?

Explain your answer.

Sundip adds some blue copper sulfate solution to the sulfuric acid. She then drops in a piece of zinc.

Sundip thinks copper sulfate is a catalyst.

Describe two things that Sundip would observe if copper sulfate is a catalyst.

Sundip uses 6.5 g of zinc and excess acid. All the zinc reacts.

Calculate the volume of hydrogen is made at room temperature and pressure.

Give your answer to 2 significant figures.

One mole of gas at room temperature and pressure has a volume of 24 dm³.

Sundip repeats (c)(i) with a catalyst present.

How does the volume of hydrogen compare with the volume calculated in part (c)(i) ?

Give one reason for your answer.

Some countries do not have enough drinkable water.

Chlorine is added to water to make it fit to drink.

The test for chlorine gas relies on two properties of chlorine.

acidic

bleaching action

green gas

reacts with metals

toxic

Explain why chlorine is added to drinking water.

Give one risk of adding chlorine to drinking water.

Beth adds a solution of sodium bromide to a sample of water.

What colour does she see if the water contains dissolved chlorine?

Write an ionic equation for this reaction.

Ammonia and its compounds are used world-wide as fertilisers.

Ammonia is made by the Haber process.

This is an equation for the reaction:

The forward reaction is exothermic.

In the Haber process a temperature of 450 °C is often used.

Nina says,

‘The Haber process should be run at a lower temperature. More ammonia is produced per day at a lower temperature.’

Discuss Nina’s statement.

Jamal, another student, says,

‘Fertilisers that contain ammonium compounds should be banned.’

Give one argument for and one argument against these types of fertilisers being banned.

Mia has three metals, A, B and C, that she reacts with water.

This is what she sees:

Metal A Fizzes and reacts quickly.

Metal B A few bubbles appear after some time.

Metal C Slow fizzing.

Which metal forms positive ions most easily?

Give one reason for your answer.

Metal A reacts with water to form A²⁺ ions.

Write the half equation for this reaction.

Explain whether metal A is being reduced or oxidised.

Metal C goes brown when put in copper sulfate solution, CuSO₄.

Metal C forms a compound that contains C²⁺ ions.

Write a balanced symbol equation for this reaction. Include state symbols.

Metals conduct electricity.

Describe how the bonding in metals explains this.

‘Tumsoothe’ is a medicine that cures indigestion.

Tumsoothe is a solution of ‘sodium bicarbonate’, NaHCO₃.

Layla puts some Tumsoothe in a beaker and places it on a balance.

She adds dilute hydrochloric acid to the contents of the beaker. CO₂ is given off.

Layla records the mass of the beaker and its contents every 10 seconds up to 60 seconds.

This is a graph of her results:

Draw a curve of best fit on the graph in Fig 12.2.

Use Fig. 12.2 to calculate the initial rate of reaction.

Initial rate of reaction =........ g / s

Describe how the rate of reaction changes with time.

Use Fig. 12.2 to estimate the total mass loss in the reaction after 100 seconds has passed.

Explain how you obtained your answer.

Layla does her experiment a second time. She uses an excess of acid and a different volume of Tumsoothe.

8 g of CO₂ is given off.

Calculate the number of moles of CO₂ given off.

Give your answer to 2 significant figures.

This is an equation for the reaction:

Calculate the mass of NaHCO₃ that reacts.

Give your answer to 2 significant figures.

Use your answer to (b)(i) to help you.

Layla wants to measure the concentration of NaHCO₃ in Tumsoothe.

She titrates her Tumsoothe solution with hydrochloric acid.

Layla measures out 25.0 cm³ of Tumsoothe. (i)

What piece of apparatus should Layla use to measure out this volume?

Layla repeats her titration three times. Her results are shown.

What can Layla do to improve the quality of her results?