Practice Paper 2 (Edexcel IGCSE Science)

Separate: Chemistry Only

A student investigates the reaction between sodium hydroxide solution and dilute sulfuric acid. He does a titration to find the concentration of the sulfuric acid. This is his plan for the titration. There are some mistakes and omissions in his plan.

• rinse a conical flask with the sodium hydroxide solution
• use a measuring cylinder to measure out 25 cm³ of the sodium hydroxide solution and add it to the conical flask
• add a few drops of methyl orange indicator to the conical flask
• rinse a burette with water and then fill it with the sulfuric acid
• add the acid from the burette to the conical flask until the indicator changes colour at the end‐point of the titration
• record the final burette reading

Give the colour change of the methyl orange indicator at the end‐point.

from ........................................................... to ................................................................

Separate: Chemistry Only

Describe four changes that the student could make to improve his plan.

Separate: Chemistry Only

The student then does the titration correctly. He finds that 16.70 cm³ of the dilute sulfuric acid neutralises 25.0 cm³ of sodium hydroxide solution of concentration 0.200 mol/dm³. The equation for the reaction is

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

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

A student making copper sulfate crystals used the method below.

Unreacted copper carbonate was left over as it had been added in excess.

What is the reason for adding it in excess and what would step 3 be of this method?

A student adds a few drops of dilute nitric acid followed by a few drops of silver nitrate solution to a test tube containing an unknown colourless solution. A white precipitate is seen.

What ions could be present in the solution?

This question is about gases.

The box gives the names of some gases.

Use gases from the box to answer these questions. Each gas may be used once, more than once or not at all.

i) Name the most abundant gas in the Earth’s atmosphere.

ii) Name the gas that is a compound.

iii) Name the least reactive of the gases.

iv) Name the gas formed by the complete combustion of hydrocarbons.

Describe the test for hydrogen gas.

This question is about Group 1 metals and their reactions.

When lithium is added to water, bubbles of hydrogen gas are observed.

i) Give two other observations that could be made.

ii) Give the test for hydrogen gas.

i) Give one observation that would be different if potassium is used instead of lithium.

ii) The diagram represents an atom of lithium and an atom of potassium.

Explain why potassium is more reactive than lithium.

The equation for the reaction between lithium and water is:

2Li (s) + 2H₂O (l) → 2LiOH (aq) + H₂ (g)

i) A mass of 0.500 g of lithium reacts with an excess of water. Calculate the volume, in cm³, of hydrogen gas produced at rtp.

[molar volume of a gas at rtp = 24 000 cm³]

Give your answer to three significant figures.

volume = .......................................... cm³

ii) In a reaction between lithium and water, 150 cm³ of lithium hydroxide solution is formed.

The lithium hydroxide solution is then completely neutralised by 24.85 cm³ of 0.100 mol/dm³ sulfuric acid. The equation for the neutralisation is

2LiOH (aq) + H₂SO₄ (aq) → Li₂SO₄ (aq) + 2H₂O (l)

Calculate the concentration, in mol/dm³, of the lithium hydroxide solution.

concentration = .............................................................. mol/dm³

This question is about some of the halogens and their compounds.

i) Which element is a liquid at room temperature?

ii) Which element has the palest colour?

iii) Which element is the least reactive?

A teacher uses displacement reactions to demonstrate the reactivities of some halogens. She adds solutions of chlorine, bromine and iodine separately to three different sodium halide solutions. The table shows some of the teacher’s results.

A change in colour of the solution indicates that a reaction has occurred.

i) Complete the table by predicting the missing results.

ii) State why the teacher does not add bromine solution to sodium bromide solution.

iii) The word equation for the reaction of bromine with sodium iodide is

bromine + sodium iodide → iodine + sodium bromide

Write a chemical equation for this reaction.

A technician sees an unlabelled bottle containing a liquid. He knows that the liquid is a solution of one of these compounds.

• copper(II) chloride
• copper(II) bromide
• iron(II) chloride
• iron(II) bromide

Describe chemical tests that the technician could use to identify the compound in the solution.

A metal is added to copper(II) sulfate solution. A displacement reaction only occurs if the metal added is more reactive than copper.

metal + copper(II) sulfate → metal sulfate + copper

Displacement reactions are exothermic. The more reactive the metal added, the greater the temperature rise. A student uses the following method in an experiment to compare the reactivities of different metals:

• Pour some copper(II) sulfate solution into a boiling tube and record its temperature using a thermometer
• Add some metal to the tube and stir with the thermometer
• Record the maximum temperature of the contents of the tube.

He repeats the method using the same amount, in moles, of different metals.

To make the experiment valid, he starts with the copper(II) sulfate solution and the added metal at the same temperature.

State two other variables that must be controlled if the experiment is to be valid.

Another student uses the same method three times for each of the metals E, F, G and H. The table shows her results for these metals.

i) The student calculates the mean temperature increase for metals E and F. She does not include anomalous values in her calculations. Calculate the mean temperature increase for metals G and H, ignoring any anomalous values. Write your answers in the table.

ii) Explain which metal is the most reactive.

iii) Explain which metal is less reactive than copper.

Methane and bromine react to form bromomethane and hydrogen bromide.

What does this reaction occur in the presence of?

The structures of some organic compounds are shown below.

Compound R can be converted to compound T by reacting it with bromine.

What kind of reaction is this?

The structures of six hydrocarbons are shown.

Which two compounds are isomers of one another?

This question is about alkenes and polymers.

Ethene (C₂H₄) can be represented by different types of formula.

i) Complete the table by giving the missing information.

ii) Ethene is a member of the homologous series of alkenes. All members of the same homologous series have the same general formula. Give two other characteristics of a homologous series.

1. ............................................................................
2. ............................................................................

Ethene is used to make poly(ethene).

i) State the type of polymerisation used to form poly(ethene).

ii) Complete the equation for the polymerisation of ethene.

iii) Poly(ethene) is used to make plastic bags. Corn starch from plants can also be used to make polymers for plastic bags. The table gives some information about poly(ethene) and polymers made from corn starch.

Use the information in the table and your knowledge to discuss the advantages and disadvantages of using poly(ethene) to make plastic bags.

The diagram shows the repeat unit of another polymer.

Draw the displayed formula of the monomer used to make this polymer.

Which is true about chemical energy changes?

Calcium carbonate reacts with hydrochloric acid to produce calcium chloride, water and carbon dioxide:

CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + H₂O (l) + CO₂ (g)

Which statement is not true if the temperature of the reaction decreases?

The diagram shows a test tube containing ammonium chloride that has been heated gently.

Which two gases are present at position Y?

The diagram shows the electronic configuration of an atom of an element.

Complete the table by giving the missing information about this atom.

This element has three isotopes. The table shows the mass number and percentage abundance of each isotope in a sample of this element.

Calculate the relative atomic mass (A_r) of this element. Give your answer to one decimal place.

Sodium hydrogencarbonate (NaHCO₃) is also known as baking soda.

Baking soda can be used to make cakes increase in size in an oven.

This is the equation for the reaction that takes place when baking soda is heated.

2NaHCO₃ (s) → Na₂CO₃ (s) + CO₂ (g) + H₂O (g)

i) What type of reaction is this?

ii) Suggest why the reaction makes the cakes increase in size.

A student uses this apparatus to investigate the reaction that takes place when sodium hydrogencarbonate is heated.

This is the student’s method.

• Weigh a crucible and record the mass
• Add some sodium hydrogencarbonate to the crucible, reweigh it and record the mass
• Heat the crucible and contents for five minutes, then allow to cool before weighing and recording the mass
• Heat the crucible and contents again for a further three minutes, then allow to cool before weighing and recording the mass

i) Give a reason why the crucible and contents are heated for a further three minutes.

ii) The student considered using a lid on the crucible in the experiment.

Suggest an advantage and a disadvantage of using a lid on the crucible.

advantage ....................................................................................................

disadvantage ....................................................................................................

The table shows some of the student’s results.

i) Calculate the mass of sodium hydrogencarbonate that the student uses.

mass = ..............................................................g

ii) Using this equation, calculate the maximum mass of sodium carbonate (Na₂CO₃) that could form in the student’s reaction.

2NaHCO₃ (s) → Na₂CO₃ (s) + CO₂ (g) + H₂O (g)

[M_r of NaHCO₃ = 84 M_r of Na₂CO₃ = 106]

maximum mass = .............................................................. g

In a second experiment, the student uses a larger mass of sodium hydrogencarbonate.

She calculates that she should obtain 4.8 g of sodium carbonate.

She actually obtains 4.2 g of sodium carbonate.

i) Calculate the percentage yield from the student’s experiment.

percentage yield = ..............................................................%

ii) Other than spillages, suggest a possible reason why the student’s actual yield is less than expected.