Edexcel IGCSE Chemistry Chemistry Paper 2 January 2022 question paper 4CH1/2CR

Two substances are needed to cause iron to rust.

Name these two substances.

The box gives the names of some substances.

Use words from the box to answer these questions.

Give the name of a non-metallic element.

Give the name of a compound.

Give the name of the metal that is lowest in the reactivity series.

Crude oil is a mixture of hydrocarbons.

This passage is about the industrial separation of crude oil.

Complete the passage by adding the missing words.

Crude oil is_........ to form vapour.

The vapour is passed through a_........ column.

The refinery gases are collected at the top of the column because they have low

Bitumen is collected at the bottom of the column.

Give one use of bitumen.

One of the hydrocarbons in crude oil is an alkane with this structural formula.

Give the name of this alkane.

Calculate the relative molecular mass (M_r) of this alkane.

Catalytic cracking is used to convert long-chain alkanes into shorter-chain alkanes.

Give the name of the catalyst and the temperature used in catalytic cracking.

Catalytic cracking also produces alkenes.

Decane (C₁₀H₂₂) can undergo cracking to give C₄H₁₀ and two different alkenes.

Complete the equation for this cracking process.

A student does a titration to find the concentration of a solution of dilute sulfuric acid.

The student uses these solutions and this apparatus.

• dilute sulfuric acid

• potassium hydroxide solution of concentration 0.240 mol / dm³

• methyl orange indicator

The student wants to find the volume of sulfuric acid needed to neutralise 25.0 cm³ of the potassium hydroxide solution.

Describe how the student should do this titration.

Assume that all pieces of apparatus are clean and dry.

The student needs 15.00 cm³ of sulfuric acid to neutralise 25.0 cm³ of the potassium hydroxide solution.

This is the equation for the reaction.

Calculate the amount, in moles, of KOH in 25.0 cm³ of potassium hydroxide solution of concentration 0.240 mol / dm³.

Calculate the amount, in moles, of H₂SO₄ in 15.00 cm³ of the sulfuric acid.

amount of H₂SO₄ =_........

Calculate the concentration, in mol / dm³, of the sulfuric acid.

concentration of sulfuric acid =_........ mol / dm

This question is about alcohols, carboxylic acids and their reactions.

The boxes give some information about a carboxylic acid.

Complete the boxes by giving the missing information.

Ethanol can be oxidised to produce a carboxylic acid.

Give the names of the two reagents used in this oxidation reaction.

Which of these colour changes occurs during the reaction?

Alcohols and carboxylic acids can be heated together to form esters.

State why it is better to heat the mixture using a water bath rather than directly with a Bunsen burner flame.

An ester has the structural formula CH₃CH₂COOCH₃

Which of these is the name of this ester?

This question is about three stages in the manufacture of sulfuric acid.

In stage 1, sulfur is burned in oxygen to form sulfur dioxide gas.

State one environmental problem caused by the release of sulfur dioxide into the atmosphere.

A mass of 6.4 tonnes of sulfur is burned to produce sulfur dioxide gas.

Calculate the maximum volume, in dm³, of sulfur dioxide gas that can be produced at rtp.

[molar volume of sulfur dioxide gas at rtp = 24 dm³]

[1 tonne = 10⁶g]

Give your answer in standard form.

In stage 2, sulfur dioxide is reacted with oxygen to form sulfur trioxide gas.

The yield of sulfur trioxide is approximately 98%.

A catalyst is used in this reaction.

Explain how a catalyst increases the rate of a reaction.

The temperature is kept constant.

Give a reason why increasing the pressure would increase the yield of sulfur trioxide.

Suggest why it is not necessary to increase the pressure in stage 2.

In stage 3, the sulfur trioxide is reacted with concentrated sulfuric acid to form a liquid called oleum, H₂S₂O₇

The oleum is then added to water to form concentrated sulfuric acid.

Complete the chemical equations for these two reactions.

Sulfuric acid reacts with ammonia to form ammonium sulfate, (NH₄)₂SO₄

Calculate the percentage by mass of nitrogen in ammonium sulfate.

[M_r of (NH₄)₂SO₄ = 132]

A teacher prepares the insoluble salt lead(II) bromide (PbBr₂) by mixing solutions of lead(II) nitrate and sodium bromide.

Describe what the teacher should do next to obtain a pure, dry sample of lead(II) bromide.

The teacher then sets up a circuit in a fume cupboard using the pure, dry sample of lead(II) bromide.

Explain why the lamp does not light when the lead(II) bromide is solid.

The teacher heats the lead(II) bromide.

When the lead(II) bromide is molten, the lamp lights and bromine forms at the positive electrode.

State what observation would be made at the positive electrode.

Explain how bromide ions in the molten lead(II) bromide become bromine molecules at the positive electrode.

Write an ionic half-equation for the reaction that occurs at the negative electrode.

Include state symbols in your equation.

The reaction between hydrogen and chlorine is exothermic.

This is the equation for the reaction.

State the meaning of the term exothermic.

The table gives the bond energies for the H H and H l bonds.

Use the equation and information from the table to calculate the bond energy of

bond energy =_........ kJ / mol

Explain why this reaction is exothermic.

Refer to bond-breaking and bond-making in your answer.

Complete the reaction profile diagram to show the position of the products, the enthalpy change (ΔH) and the activation energy (E_a) for the reaction.