IGCSE Chemistry 0620 Paper 43, May/June 2024

produce ammonia from nitrogen

produce lead from molten lead(II) bromide

separate an insoluble solid from a mixture of an insoluble solid and a solution

produce ethanol from ethene

identify the components of a mixture of soluble coloured substances

separate a mixture of several liquids with different boiling points

determine the volume of an acid required to neutralise a given volume of an alkali.

Some properties of graphite, oxygen and carbon monoxide are shown in Table 3.1. Table 3.1

Explain why graphite conducts electricity when solid.

Complete the dot-and-cross diagram in Fig. 3.1 of a molecule of oxygen. Show outer shell electrons only.

Deduce the physical state of carbon monoxide at $-195{}^{\circ }\text{C}$. Use the data in Table 3.1 to explain your answer. physical state ...................................................................................................................... explanation ......................................................................................................................... .............................................................................................................................................

Explain in terms of structure and bonding why graphite has a much higher melting point than carbon monoxide.

Potassium reacts with chlorine to form potassium chloride. Write a symbol equation for this reaction.

A dilute aqueous solution of potassium chloride undergoes electrolysis. Oxygen is produced at the anode. State what is meant by the term electrolysis.

Write an ionic half-equation for the production of oxygen at the anode.

Describe a reversible reaction at equilibrium in terms of: ● the rate of the forward reaction and the rate of the reverse reaction .................................................................................................................................................... ● the concentration of reactants and products. ....................................................................................................................................................

The pressure of the mixture is increased. All other conditions stay the same. The mixture immediately turns darker brown before the position of equilibrium changes. Explain in terms of particles why the mixture immediately turns darker brown.

The temperature of the mixture is increased. All other conditions stay the same. The mixture turns darker brown. State what can be deduced about the forward reaction from this information.

Sulfur is converted into sulfuric acid, ${\text{H}}_2{\text{SO}}_4$, by a series of reactions. Sulfur dioxide, ${\text{SO}}_2$, and oxygen, ${\text{O}}_2$, react to form sulfur trioxide, ${\text{SO}}_3$. The reversible reaction reaches equilibrium. $$2{\text{SO}}_2\text{(g)}+{\text{O}}_2\text{(g)}\rightleftharpoons 2{\text{SO}}_3\text{(g)}$$ Complete Table 4.1 using only the words, increases, decreases or no change. Table 4.1

Deduce the oxidation number of sulfur in: S .................................................. ${\text{SO}}_3$ ..............................................

Barium sulfate, ${\text{BaSO}}_4$, is an insoluble salt and is made by precipitation. Name two aqueous solutions that produce a precipitate of barium sulfate when they are mixed. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Describe how to produce a pure sample of barium sulfate from the mixture of aqueous solutions in (a)(i).

Write an ionic equation for the precipitation reaction which produces barium sulfate. Include state symbols.

Soluble salts are made from dilute acids. Name the dilute acid and one other substance that react together to make copper(II) sulfate. dilute acid .................................................................................................................. other substance .........................................................................................................

Nitrates decompose when they are heated. When hydrated copper(II) nitrate is heated, oxygen gas is produced. Describe a test for oxygen. test ...................................................................................................................................... observations .......................................................................................................................

Complete the equation for the decomposition of hydrated copper(II) nitrate. $$2{\text{Cu(NO}}_3{)}_2\bullet 3{\text{H}}_2\text{O}\to \mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\text{CuO}+\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}{\text{NO}}_2+{\text{O}}_2+\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}{\text{H}}_2\text{O}$$

Hydrated zinc sulfate gives off water when it is heated. $${\text{ZnSO}}_4\bullet x{\text{H}}_2\text{O(s)}\to {\text{ZnSO}}_4\text{(s)}+x{\text{H}}_2\text{O(g)}$$ A student does an experiment to determine the value of $x$ in ${\text{ZnSO}}_4\bullet x{\text{H}}_2\text{O}$. step 1 The student weighs a sample of hydrated zinc sulfate. step 2 The student heats the sample of hydrated zinc sulfate. step 3 The student weighs the solid after heating. step 4 The student repeats step 2 and step 3 until the mass of solid after heating is constant. State why the student does step 4.

In an experiment, $0.574\text{ g}$ of ${\text{ZnSO}}_4\bullet x{\text{H}}_2\text{O}$ is heated until the mass is constant. The mass of ${\text{ZnSO}}_4$ that remains is $0.322\text{ g}$. [$M_{\text{r}}$: ${\text{ZnSO}}_4$, 161; ${\text{H}}_2\text{O}$, 18] Determine the value of $x$ using the following steps. ● Calculate the number of moles of ${\text{ZnSO}}_4$ remaining. .............................. mol ● Calculate the mass of ${\text{H}}_2\text{O}$ given off. .............................. g ● Calculate the number of moles of ${\text{H}}_2\text{O}$ given off. .............................. mol ● Determine the value of $x$. $x=$ ..............................

Fig. 6.1 shows a blast furnace used to extract iron from its ore. Name the main ore of iron used in the blast furnace.

Name the substance that enters the blast furnace at A.

Name the reducing agent in the extraction of iron in the blast furnace.

Explain why limestone is added to the blast furnace. Give details of the chemical reactions that are involved.

The list shows the properties of some elements. ● act as catalysts ● have low densities ● have low melting points ● form acidic or basic oxides ● form coloured compounds ● form positive or negative ions Iron is a transition metal. Sodium is a Group I metal. State which property from the list: is true for sodium but not iron

State which property from the list: is true for iron but not sodium

State which property from the list: is true for both sodium and iron

State which property from the list: is not true for sodium and not true for iron.

Steel consists mainly of iron. Iron rusts when it reacts with water and oxygen. Fig. 6.2 shows magnesium blocks attached to the bottom of a steel boat. The magnesium does not completely cover the steel. The magnesium blocks provide sacrificial protection for the steel. Explain, in terms of electrons, why magnesium is used for sacrificial protection.

Name a metal that cannot provide sacrificial protection for steel.

An organic compound A has the following composition by mass. $$\text{C, }83.33\mathrm{\%};\text{H, }16.67\mathrm{\%}$$ Calculate the empirical formula of compound A. empirical formula = ..............................

Compound B has the empirical formula ${\text{C}}_2{\text{H}}_5$ and a relative molecular mass of 58. Determine the molecular formula of compound B. molecular formula = ..............................

Fig. 7.1 shows a section of a polymer formed from an alkene. Identify the functional group in alkenes that reacts when alkenes form polymers.

A section of a polymer is shown in Fig. 7.1. ● Draw the displayed formula of the monomer that forms this polymer. ● Name the monomer used to form this polymer. .............................................................................................................................................

Alkenes are produced by cracking alkanes. When ${\text{C}}_{12}{\text{H}}_{26}$ is cracked, the products are ethene and an alkane which form in a 2:1 mole ratio. Write a symbol equation for this reaction. $${\text{C}}_{12}{\text{H}}_{26}\to \text{........................}+\text{...................................................}$$

State the general formula for alcohols.

Draw the displayed formula of one alcohol with the molecular formula ${\text{C}}_3{\text{H}}_8\text{O}$. Name the alcohol you have drawn. name of alcohol ..................................................................................................................