Edexcel IGCSE Chemistry Chemistry Paper 2 November 2020 question paper 4CH1/2CR

The diagram shows some pieces of apparatus.

Complete the table by giving the name of each piece of apparatus.

Which piece of apparatus can be used to measure the volume of a liquid?

Thallium, Tl, is an element in Group 3 and Period 6 of the Periodic Table.

The atomic number of thallium is 81

How many electrons are there in the outer shell of an atom of thallium?

A thallium ion has a charge of 3+

How many electrons are there in this thallium ion?

A sample of thallium contains two isotopes.

The table shows the mass number and percentage abundance of each isotope in the sample.

Give the number of protons and the number of neutrons in one atom of the thallium-205 isotope.

number of protons_........

number of neutrons_........

Calculate the relative atomic mass of this sample of thallium.

Give your answer to one decimal place.

The diagram shows a fractionating column used to separate crude oil into fractions.

Give a use for bitumen and a use for gasoline.

Explain why bitumen is collected at the bottom of the fractionating column and gasoline is collected near the top of the fractionating column.

There is a low demand for some of the fractions obtained from crude oil.

Cracking can be used to convert these fractions into more useful substances.

State the conditions needed for cracking.

Dodecane (C₁₂H₂₆) can be cracked to produce an alkane and two alkenes.

Complete the equation by giving the formulae of the two alkenes.

This question is about some of the alkali metals and their compounds.

When a teacher drops a small piece of sodium into a trough of cold water, she observes bubbles of gas.

Give two other observations that would be made when sodium reacts with cold water.

Lithium reacts with fluorine to form the compound lithium fluoride.

Give a chemical equation for this reaction.

Give a test to show that lithium fluoride contains lithium ions.

Draw diagrams to show the arrangement of the electrons in a lithium ion and in a fluoride ion.

Include the charge on each ion.

lithium ion
fluoride ion

The table shows the electronic configurations of sodium and potassium.

Explain, in terms of their electronic configurations, why potassium is more reactive than sodium.

This question is about the metal aluminium.

Draw a labelled diagram to represent the structure and bonding in a metal.

Explain why a metal conducts electricity.

Aluminium is used to make cans for drinks.

Give two properties of aluminium that make it suitable for this use.

Aluminium is extracted from aluminium oxide (Al₂O₃) by electrolysis.

The electrolyte is aluminium oxide dissolved in molten cryolite.

State why aluminium cannot be extracted by heating aluminium oxide with carbon.

Aluminium is produced at the negative electrode.

The ionic half-equation for the reaction is

State why this is a reduction reaction.

Complete the ionic half-equation for the reaction at the positive electrode.

A student wants to prepare sodium chloride crystals from sodium hydroxide solution and dilute hydrochloric acid.

He does a titration to find the volume of dilute hydrochloric acid needed to neutralise the sodium hydroxide solution.

This is his method.

● add 25.0 cm³ of sodium hydroxide solution to a conical flask

● add a few drops of phenolphthalein indicator to the conical flask

● titrate the solution with the hydrochloric acid

Name a suitable piece of apparatus that the student should use to measure 25.0 cm³ of sodium hydroxide solution.

Give the colour of the phenolphthalein indicator in sodium hydroxide solution and in hydrochloric acid.

colour in sodium hydroxide solution_........

colour in hydrochloric acid_........

Suggest why universal indicator is never used in a titration.

The student finds that 21.50 cm³ of hydrochloric acid is needed to neutralise 25.0 cm³ of sodium hydroxide solution.

Describe what the student should do next to prepare a pure solution of sodium chloride.

Describe how the student could obtain dry crystals of sodium chloride from the pure sodium chloride solution.

The student needs 21.50 cm³ of hydrochloric acid to neutralise 25.0 cm³ of sodium hydroxide solution of concentration 0.800 mol/dm³.

The equation for the reaction is

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

concentration =_........ mol/dm

Ethanol, C₂H₅OH, can be oxidised to produce ethanoic acid, CH₃COOH, by heating it with potassium dichromate(VI).

Name one other reactant needed for this reaction to occur.

Which colour change occurs during this reaction?

When ethanol is burned in air, complete combustion can occur.

The equation for this reaction is

This equation can also be written using displayed formulae to show all the covalent bonds in the molecules.

H H

H H

The table gives the bond energies for these bonds.

Use values from the table to calculate the energy needed to break all the bonds in the reactants.

energy needed_........

Use values from the table to calculate the energy released when all the bonds in the products are formed.

energy released_........

Calculate the molar enthalpy change (Δ H) in kJ/mol, for the complete combustion of ethanol.

Include a sign in your answer.

ΔH =_........ kJ/mol

Ethanol reacts with methanoic acid, HCOOH, in the presence of an acid catalyst to form an ester.

The equation for the reaction is

Give the name of the ester that forms.

Draw the displayed formula for this ester.

When this reaction takes place in a sealed container, the reaction can reach dynamic equilibrium.

Give two characteristics of a reaction at dynamic equilibrium.

Methanoic acid reacts with sodium carbonate to form sodium methanoate, carbon dioxide and water.

The equation for the reaction is

Calculate the volume, in cm³, of carbon dioxide gas produced when 2.3 g of methanoic acid reacts completely with sodium carbonate.

[M_r of HCOOH = 46]

[molar volume of carbon dioxide at rtp = 24 dm³]