O Level Chemistry 5070 Paper 22, Oct/Nov 2024

Fig. 1.1 shows the electronic configurations of five atoms, A, B, C, D and E. Answer the questions about these electronic configurations. Each electronic configuration may be used once, more than once or not at all. State which electronic configuration, A, B, C, D or E, represents: an atom of a noble gas

an atom of an element that is used in food containers because of its resistance to corrosion

an atom of an element in Group V of the Periodic Table

an atom of an element in Period 3 of the Periodic Table

an atom that forms a stable ion with a charge of 2–.

Deduce the number of protons and neutrons in the vanadium atom shown. ${}_{23}^{51}\mathrm{V}$ number of protons .................................................................................................................... number of neutrons ..................................................................................................................

In step 1, carbon burns in air to produce carbon dioxide. Give one other reason why carbon is burned in air in the blast furnace.

In step 2, carbon monoxide is produced by the reaction of carbon dioxide with carbon. State one adverse effect of carbon monoxide on health.

In step 3, iron(III) oxide is reduced by carbon monoxide. Write the symbol equation for this reaction.

Explain why calcium carbonate is added to the blast furnace. Include any relevant reactions or equations in your answer.

Iron is a transition element. Transition elements have high melting and boiling points. State two other properties that are typical of transition elements but not of Group I metals. 1 ................................................................................................................................................ 2 ................................................................................................................................................

Iron is prevented from rusting by galvanising with zinc. Explain two different ways in which zinc prevents rusting.

The equation shows the reaction of iron with steam in a closed container. $$3\mathrm{F}\mathrm{e}(\mathrm{s})+4{\mathrm{H}}_2\mathrm{O}(\mathrm{g})\rightleftharpoons {\mathrm{F}\mathrm{e}}_3{\mathrm{O}}_4(\mathrm{s})+4{\mathrm{H}}_2(\mathrm{g})$$ Predict and explain what happens to the position of equilibrium when the pressure is increased. The temperature remains the same. prediction .................................................................................................................................. explanation ...............................................................................................................................

${\mathrm{F}\mathrm{e}}_3{\mathrm{O}}_4$ reacts with concentrated hydrochloric acid. The products are iron(II) chloride, iron(III) chloride and a liquid that turns blue cobalt(II) chloride paper pink. Construct the symbol equation for this reaction.

Define the term electrolysis.

Label the anode on Fig. 3.1.

Name the product at the cathode.

Oxygen is formed at the anode. Construct the ionic half-equation for the reaction at the anode.

Name a suitable element other than graphite that is used for the electrodes in this electrolysis.

Butane belongs to the alkane homologous series. Members of the same homologous series have the same functional group and the same general formula. State two other characteristics of a homologous series. 1 ................................................................................................................................................ 2 ................................................................................................................................................

Fig. 4.1 shows the displayed formula of butane. Explain how Fig. 4.1 shows that butane is a saturated compound.

Give the structural formula of butane.

Nonane, ${\mathrm{C}}_9{\mathrm{H}}_{20}$, is present in the naphtha fraction from the distillation of petroleum. State one use of the naphtha fraction.

When nonane is cracked, shorter hydrocarbon molecules are formed. Construct the symbol equation for a reaction in which nonane is cracked and the only products are propane and ethene.

Propane reacts with chlorine in the presence of ultraviolet light. Fig. 4.2 shows the displayed formulae of the reactants and products. Name the type of chemical reaction that takes place.

State the purpose of the ultraviolet light in this reaction.

Calculate the enthalpy change of this reaction in $\mathrm{k}\mathrm{J}\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$. Use the bond energies in Table 4.1. Table 4.1

enthalpy change = ................................................... $\mathrm{k}\mathrm{J}\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$

The equation shows the reaction of ethene with chlorine. $${\mathrm{C}}_2{\mathrm{H}}_4+{\mathrm{C}\mathrm{l}}_2\to {\mathrm{C}}_2{\mathrm{H}}_4{\mathrm{C}\mathrm{l}}_2$$ Explain how this equation shows that this reaction is an addition reaction.

Complete the equation by adding state symbols for the products. $$\mathrm{Z}\mathrm{n}(\mathrm{s})+2\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})\to {\mathrm{Z}\mathrm{n}\mathrm{C}\mathrm{l}}_2(\dots )+{\mathrm{H}}_2(\dots )$$

Fig. 5.1 shows how the volume of hydrogen changes with time as the reaction proceeds. Describe how the shape of the curve in Fig. 5.1 shows that the rate of reaction decreases with time.

Explain in terms of collision theory why the rate of reaction decreases with time.

The student repeats the experiment using the same mass of powdered zinc instead of large pieces of zinc. All other conditions stay the same. Describe and explain the difference in rate of reaction when powdered zinc is used.

Excess zinc is added to $16.0{\mathrm{c}\mathrm{m}}^3$ of $0.400{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ hydrochloric acid. Calculate the volume of hydrogen gas released measured at room temperature and pressure. Give your answer to two significant figures. volume of hydrogen gas = .................................................. ${\mathrm{d}\mathrm{m}}^3$

The reaction of zinc with hydrochloric acid is exothermic. Complete the reaction pathway diagram in Fig. 5.2 to show: • the reactants and products • a labelled arrow for the activation energy, $E_{\mathrm{a}}$ • a labelled arrow for the enthalpy change, $\mathrm{\Delta }H$.

Describe the observations made when: • a few drops of aqueous ammonia are added to an aqueous solution containing zinc ions ........................................................................................................................................... • excess aqueous ammonia is added to an aqueous solution containing zinc ions. ...........................................................................................................................................

Describe how to prepare pure, dry crystals of zinc chloride after reacting excess zinc with dilute hydrochloric acid.

Explain why boron nitride has a high melting point. Use the information in Fig. 6.1.

Explain why hydrazine is a poor electrical conductor. Use the information in Fig. 6.1.

Complete Fig. 6.2 to show the dot-and-cross diagram for the electronic configuration of hydrazine. Show only the outer shell electrons.

The ionic equation for the reaction of nitride ions with water is shown. $${\mathrm{N}}^{3-}+3{\mathrm{H}}_2\mathrm{O}\to {\mathrm{N}\mathrm{H}}_3+3{\mathrm{O}\mathrm{H}}^{-}$$ The oxidation number of hydrogen in ${\mathrm{N}\mathrm{H}}_3$ is $+1$. Deduce the oxidation number of nitrogen in ${\mathrm{N}\mathrm{H}}_3$.

Explain why this is not a redox reaction by referring to the oxidation number of nitrogen.

Boron oxide reacts with magnesium as shown. $${\mathrm{B}}_2{\mathrm{O}}_3+3\mathrm{M}\mathrm{g}\to 2\mathrm{B}+3\mathrm{M}\mathrm{g}\mathrm{O}$$ $8.0\mathrm{g}$ of boron oxide is reacted with $7.2\mathrm{g}$ of magnesium. Show by calculation that boron oxide is in excess.

State the name given to a formula such as ${\mathrm{C}}_n{\mathrm{H}}_{2n}{\mathrm{O}}_2$.

Deduce the value of $n$ in the ester propyl ethanoate.

The ester ethyl butanoate is produced by reacting ethanol with butanoic acid. Draw the displayed formula of ethyl butanoate.

Fig. 7.1 shows the simplified structures of two molecules that combine to form a polyester. Complete the diagram in Fig. 7.2 to show the structure of two repeat units of this polyester. Show all of the atoms and all of the bonds in the linkages.

Name the type of polymerisation in this reaction.

PET is a plastic. Describe the chemical processes involved in converting used PET into a new plastic.

Ethanoic acid reacts with sodium carbonate. Name the three products of this reaction. 1 ........................................................................................................................................ 2 ........................................................................................................................................ 3 ........................................................................................................................................

Ethanoic acid is a liquid at room temperature. Describe the arrangement and motion of the particles in a liquid. arrangement ...................................................................................................................... ........................................................................................................................................... motion ............................................................................................................................... ...........................................................................................................................................