IGCSE Chemistry 0620 Paper 43, May/June 2023

photosynthesis

an addition reaction

a precipitation reaction

incomplete combustion

a displacement reaction

a substitution reaction.

The symbols of the elements in Period 3 of the Periodic Table are shown. Na Mg Al Si P S Cl Ar Use the symbols of the elements in Period 3 to answer the questions that follow. Each symbol may be used once, more than once, or not at all. Give the symbol of the element that: is present in purified bauxite

contains atoms with a full outer shell of electrons

is used to kill microbes in water treatment

forms an amphoteric oxide

forms an oxide which causes acid rain

has an oxidation number of –1 when it forms a compound with hydrogen.

The relative atomic masses of elements can be calculated from the relative masses of isotopes and their percentage abundances. Identify the isotope to which all relative masses are compared.

Table 2.1 shows the relative masses and the percentage abundances of the two isotopes in a sample of magnesium. Table 2.1

Calculate the relative atomic mass of magnesium to one decimal place. relative atomic mass = ..............................

An ion contains 10 electrons, 13 protons and 14 neutrons. State the nucleon number of the ion.

Identify the element that forms this ion.

Magnesium reacts with fluorine to form the ionic compound magnesium fluoride. The electronic configurations of an atom of magnesium and an atom of fluorine are shown in Fig. 3.1. Ions are formed by the transfer of electrons from magnesium atoms to fluorine atoms. Complete the dot-and-cross diagrams in Fig. 3.2 to show the electronic configurations of one magnesium ion and one fluoride ion. Show the charges on the ions.

Deduce the formula of magnesium fluoride.

When solid magnesium fluoride is dissolved in water it forms a solution that conducts electricity. State one other change that can be made to solid magnesium fluoride to allow it to conduct electricity.

Silicon tetrachloride, ${\mathrm{S}\mathrm{i}\mathrm{C}\mathrm{l}}_4$, and silicon(IV) oxide, ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$, are covalent compounds. Complete the dot-and-cross diagram in Fig. 3.3 to show the electronic configuration in a molecule of silicon tetrachloride. Show outer shell electrons only.

The melting points of silicon tetrachloride and silicon(IV) oxide are shown in Table 3.1. Table 3.1

Silicon tetrachloride has a low melting point because it has weak forces of attraction between particles. Name the type of particles that are held together by these weak forces of attraction.

Explain, in terms of structure and bonding, why silicon(IV) oxide has a high melting point.

A student carries out an experiment using excess zinc and dilute sulfuric acid. The student measures the volume of hydrogen produced at regular time intervals using the apparatus shown in Fig. 4.1. Lumps of zinc are used. The rate of reaction decreases as the reaction progresses. The rate eventually becomes zero. Explain why the rate of reaction decreases as the reaction progresses.

Explain why the rate of reaction eventually becomes zero.

The experiment is repeated using powdered zinc instead of lumps of zinc. All other conditions remain the same. Explain, in terms of collision theory, why the rate of reaction increases if powdered zinc is used.

The equation for the reaction is shown. $$\mathrm{Z}\mathrm{n}(\mathrm{s})+{\mathrm{H}}_2{\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})\to {\mathrm{Z}\mathrm{n}\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})+{\mathrm{H}}_2(\mathrm{g})$$ $25.0{\mathrm{c}\mathrm{m}}^3$ of $2.00{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ ${\mathrm{H}}_2{\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})$ is added to excess zinc. Calculate the volume of ${\mathrm{H}}_2$ formed at room temperature and pressure (r.t.p.). The volume of one mole of any gas is $24{\mathrm{d}\mathrm{m}}^3$ at r.t.p. Use the following steps. • Calculate the number of moles of ${\mathrm{H}}_2{\mathrm{S}\mathrm{O}}_4$ used. .............................. mol • Deduce the number of moles of ${\mathrm{H}}_2$ produced. .............................. mol • Calculate the volume of ${\mathrm{H}}_2$ formed at r.t.p. .............................. ${\mathrm{d}\mathrm{m}}^3$

Hydrogen can also be produced by the reaction of zinc with dilute hydrochloric acid. Write a symbol equation for this reaction.

State the test for hydrogen gas. test ...................................................................................................................................... positive result ......................................................................................................................

Aqueous copper(II) sulfate is an electrolyte. The electrolysis of aqueous copper(II) sulfate using inert electrodes forms: • copper at the cathode • oxygen at the anode. State what is meant by the term electrolyte.

State the term given to the Roman numeral, (II), in the name copper(II) sulfate.

State what happens to the colour of the aqueous copper(II) sulfate as this electrolysis progresses.

Write an ionic half-equation for the formation of copper at the cathode.

Give the formula of the ion that forms oxygen at the anode.

The electrolysis of aqueous copper(II) sulfate is repeated using copper electrodes. State what happens to the anode.

Spoons can be electroplated with silver. Name the substances used as: the anode (positive electrode) ............................................................................................ the cathode (negative electrode) ........................................................................................ the electrolyte. ....................................................................................................................

State two reasons why spoons are electroplated. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Hydrogen–oxygen fuel cells can be used to produce electricity to power cars. Petrol produces carbon dioxide and carbon monoxide when it powers cars. State one adverse effect of carbon dioxide and carbon monoxide. carbon dioxide .................................................................................................................... carbon monoxide ................................................................................................................

State one disadvantage, other than cost, of using hydrogen–oxygen fuel cells to power cars compared to using petrol.

Ammonia is manufactured by the reaction between nitrogen and hydrogen in the Haber process. The equation is shown. $${\mathrm{N}}_2(\mathrm{g})+3{\mathrm{H}}_2(\mathrm{g})\rightleftharpoons 2{\mathrm{N}\mathrm{H}}_3(\mathrm{g})$$ State the source of nitrogen for the Haber process.

State the source of hydrogen for the Haber process.

State the typical conditions used in the Haber process. temperature ......................................... °C pressure ............................................... atm

Name the catalyst used in the Haber process.

State what is meant by the term catalyst.

Ammonia is converted into nitric acid. The first stage is the conversion of ammonia into nitrogen monoxide, NO. The equation is shown. $$4{\mathrm{N}\mathrm{H}}_3(\mathrm{g})+5{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 4\mathrm{N}\mathrm{O}(\mathrm{g})+6{\mathrm{H}}_2\mathrm{O}(\mathrm{g})$$ The reaction is carried out at a temperature of 900°C and a pressure of 7 atm. The forward reaction is exothermic. Using explanations that do not involve cost: • explain why a temperature less than 900°C is not used ............................................................................................................................................. • explain why a pressure greater than 7 atm is not used. .............................................................................................................................................

In the second stage, nitrogen monoxide reacts with water and oxygen to produce nitric acid. Balance the symbol equation for the reaction. .....NO + .....O2 + .....H2O → .....HNO3

A student makes aqueous copper(II) nitrate by adding an excess of solid copper(II) carbonate to dilute nitric acid. Write the symbol equation for this reaction.

State two observations that indicate the copper(II) carbonate is in excess. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Name one compound, other than copper(II) carbonate, that can be added to dilute nitric acid to produce aqueous copper(II) nitrate.

Propane and chlorine react at room temperature. An equation for the reaction is shown. $${\mathrm{C}}_3{\mathrm{H}}_8+{\mathrm{C}\mathrm{l}}_2\to {\mathrm{C}}_3{\mathrm{H}}_7\mathrm{C}\mathrm{l}+\mathrm{H}\mathrm{C}\mathrm{l}$$ State the condition required for this reaction.

Draw the displayed formulae of two structural isomers with the formula ${\mathrm{C}}_3{\mathrm{H}}_7\mathrm{C}\mathrm{l}$.

Alkenes are a homologous series of hydrocarbons. State two characteristics that all members of the same homologous series have in common. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Addition polymers are made from alkenes. Complete Fig. 7.1 to show one repeat unit of the addition polymer formed from but-2-ene.

A repeat unit of a condensation polymer is shown in Fig. 7.2. The polymer is made from two monomers. Draw the structures of the monomers used to produce the polymer in Fig. 7.2.

Name the type of condensation polymer in Fig. 7.2.

Name the two homologous series to which the monomers in (i) belong. 1 .......................................................................................................................................... 2 ..........................................................................................................................................