IGCSE 2019 4CH1/2C June (pdf)
- The diagram shows the particles in an atom of an element.
(a) The box gives the names of some particles
Use words from the box to label the diagram.
(b) Give the mass number of this atom.
(c) Complete the sentence about isotopes.
- The table gives some information about the halogens, chlorine, bromine and iodine
(a) Complete the table.
(b) Chlorine has two isotopes of mass numbers 35 and 37
The relative percentage of each isotope in a sample of chlorine is
chlorine-35 77.78% chlorine-37 22.22%
Calculate the relative atomic mass of this sample of chlorine.
Give your answer to one decimal place.
(c) A student is given an aqueous solution of chlorine and an aqueous solution of
Explain how he can use these two solutions to compare the reactivity of chlorine
with the reactivity of bromine.
- Methanol, ethanol, propanol and butanol are alcohols. They are all liquids that
evaporate easily when warmed.
A student uses this apparatus to compare the time taken for the four liquids to evaporate
She uses this method.
- pour some methanol into an evaporating basin
- place the evaporating basin on top of a beaker containing hot water
- measure the time taken for the methanol to evaporate completely
- repeat the experiment with each of the other alcohols, using the same apparatus
(a) State two variables the student should control to make sure her results are valid
(b) State why it is not safe to heat the evaporating basin directly with a Bunsen flame
(c) The table shows the results of experiments done by four students, A, B, C and D.
(i) Calculate the mean (average) time for butanol to evaporate
(ii) Explain how the results show which alcohol evaporates most easily.
(iii) State the relationship between the number of carbon atoms in the molecule
and how easily the alcohol evaporates
- This question is about metals.
(a) Which statement describes metallic bonding?
(b) Aluminium is malleable and can be easily shaped to make saucepans used for
State two other properties of aluminium that make it suitable for saucepans used
for cooking food.
(c) Magnalium is an alloy of aluminium and magnesium.
The diagram shows how the atoms are arranged in this alloy.
(i) State what is meant by the term alloy.
(ii) Explain why magnalium is harder than aluminium.
- During the Second World War, engineers developed a rocket-powered aircraft.
The aircraft carried these two liquids
- hydrazine, N2H4
- hydrogen peroxide, H2O2
When these two liquids mix in the combustion chamber, they evaporate and then
react rapidly to form nitrogen gas, N2, and steam, H2O
The reaction is exothermic.
The equation for the reaction is
The displayed formulae for the reactants and products are
(a) The tables give the bond energies for the bonds broken in the reactants and the
bonds made in the products.
(i) Use the data in the tables to calculate the total amount of energy required to
break all of the bonds in the reactants.
(ii) Use the data in the tables to calculate the total amount of energy released
when all of the bonds in the products are made.
(iii) Calculate the enthalpy change, ΔH, in kJ/mol, for the reaction.
Include a sign in your answer.
(b) Explain, in terms of bonds broken and bonds made, why this reaction is exothermic.
(c) Draw an energy level diagram for the reaction between N2H4 and H2O2
- Some cars in Brazil use ethanol, C2H5OH, as a fuel instead of petrol.
The ethanol is made by the fermentation of glucose which is obtained from sugar cane.
The sugar is extracted from the sugar cane and then dissolved in water to make
a sugar solution.
(a) (i) Name the substance that is added to the sugar solution that causes glucose to ferment.
(ii) Which temperature is the most suitable for fermentation?
(iii) Explain why fermentation is done in the absence of air.
(b) (i) State what is meant by the term fuel.
(ii) Write a chemical equation for the complete combustion of ethanol in air
(c) Ethanol is also manufactured by reacting steam with ethene, C2H4
The equation for this reaction is
C2H4(g) + H2O(g) → C2H5OH(g)
State the conditions of temperature and pressure used in this process.
(d) When ethanol is heated with acidified potassium dichromate(VI), it is oxidised to
(i) State the colour change that occurs in the potassium dichromate(VI) during
(ii) The structural formula of ethanoic acid is CH3COOH
Draw the displayed formula of ethanoic acid
(iii) Complete the equation for the reaction of ethanoic acid with sodium.
- Dinitrogen tetraoxide, N2O4, is a colourless gas.
Nitrogen dioxide, NO2, is a brown gas.
The two gases can exist together in dynamic equilibrium according to the equation
(a) Explain what is meant by the term dynamic equilibrium
(b) Some N2O4 and some NO2 are put into a sealed gas syringe and allowed to form an equilibrium mixture.
This equilibrium mixture is brown.
(i) The pressure of the gas in the syringe is increased by pushing in the piston.
The mixture is then allowed to reach a new equilibrium at the same
temperature as before.
Explain why the new equilibrium mixture contains less NO2 than the original
(ii) A student suggests that the new equilibrium mixture would be lighter in
colour than the original equilibrium mixture, as there is now less NO2 present.
Suggest why the new equilibrium mixture is actually darker than the original.
(c) Carbon monoxide, CO, and oxides of nitrogen are produced in a car engine when
petrol is burned.
These oxides can be partly removed by using a catalytic converter fitted to the
car’s exhaust system.
(i) State how oxides of nitrogen are produced in the car engine.
(ii) Give a disadvantage of allowing oxides of nitrogen to escape into the atmosphere
(iii) Write a chemical equation for the reaction between nitrogen monoxide, NO,
and carbon monoxide to form carbon dioxide and nitrogen.
- The concentration of NaClO(aq) in a solution of bleach is found by reacting it with
The equation for the reaction is
NaClO(aq) + 2HCl(aq) → NaCl(aq) + H2O(l) + Cl2(g)
An excess of dilute hydrochloric acid is added to 4.00cm3 of bleach solution.
60.0cm3 of chlorine gas is produced.
(a) Explain a safety precaution that should be taken when doing this experiment.
(b) (i) Calculate the amount, in moles, of chlorine gas produced.
Assume one mole of chlorine gas occupies 24000cm3.
(ii) Determine the amount, in moles, of NaClO in 4.00cm3 of bleach.
(iii) Calculate the concentration, in mol/dm3, of the bleach solution.
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