O Level Chemistry 5070 Paper 22, May/June 2026

is an amphoteric oxide

has a molecule containing only two atoms

has a molecule with only 10 electrons

has an element with an oxidation number of +3

is an alkane.

A sample of $13.0\mathrm{g}$ of potassium superoxide reacts with excess carbon dioxide. Calculate the volume of oxygen, measured at r.t.p., that is formed. Give your answer to three significant figures. volume of oxygen = .................................................. ${\mathrm{d}\mathrm{m}}^3$

Potassium superoxide is an ionic compound. Deduce the formula of a superoxide ion.

Potassium superoxide has a giant ionic lattice. Explain what is meant by the term giant ionic lattice.

Describe the separation, arrangement and motion of particles in solid carbon dioxide.

Draw a dot-and-cross diagram to show the electronic configuration in a molecule of carbon dioxide. Show only the outer shell electrons.

Explain why carbon dioxide has a low boiling point.

Complete the reaction pathway diagram in Figure 3.1 for this decomposition reaction. Label the: • axes • reactants and products • enthalpy change, $\mathrm{\Delta }H$.

The rate of the decomposition reaction is increased by using a catalyst. Explain how a catalyst increases the rate of the decomposition reaction.

Suggest why it is important that the solid catalyst in a catalytic converter has a large surface area.

The rate of the decomposition reaction increases when the pressure of the reactants is increased at constant temperature. Explain why.

The rate of the decomposition reaction increases when the temperature of the reactants is increased at constant pressure. Explain why.

The electrolysis of aqueous copper(II) sulfate is done using copper or graphite electrodes. Complete Table 4.1 about the observations made in the two electrolysis reactions. Table 4.1

Molten barium iodide is electrolysed using graphite electrodes. Construct ionic half-equations to show the reactions at the anode and at the cathode. anode ........................................................................................................................ cathode .....................................................................................................................

Graphite is a suitable material for the electrodes used in electrolysis because it is inert and has good electrical conductivity. State the meaning of the word inert.

Name one metal that is used as an inert electrode.

The ionic equation for the reaction between magnesium and aqueous copper(II) sulfate is shown. $$\mathrm{M}\mathrm{g}(\mathrm{s})+{\mathrm{C}\mathrm{u}}^{2+}(\mathrm{a}\mathrm{q})\to {\mathrm{M}\mathrm{g}}^{2+}(\mathrm{a}\mathrm{q})+\mathrm{C}\mathrm{u}(\mathrm{s})$$ State the oxidation number of copper in copper(II) sulfate.

The reaction is an example of a redox reaction. Explain how the equation shows that both oxidation and reduction take place during the reaction. oxidation ............................................................................................................................ ........................................................................................................................................... reduction ........................................................................................................................... ...........................................................................................................................................

Use the equation to predict one observation made during this reaction.

Explain why an excess of zinc is used in this preparation.

A sample of $3.24\mathrm{g}$ of zinc is added to $50.0{\mathrm{c}\mathrm{m}}^3$ of $1.50{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ hydrochloric acid. Show by calculation that the zinc is in excess.

State how excess zinc is removed from the reaction mixture.

Describe how pure dry zinc chloride crystals are prepared from aqueous zinc chloride.

The formula of a sample of zinc chloride crystals is ${\mathrm{Z}\mathrm{n}\mathrm{C}\mathrm{l}}_2\cdot 3{\mathrm{H}}_2\mathrm{O}$. Calculate the percentage by mass of water of crystallisation in these crystals. percentage by mass = .........................................................

Describe the effect of adding aqueous ammonia drop by drop until in excess to a sample of aqueous zinc chloride.

Explain why both metals have good electrical conductivity. Use ideas about structure and bonding.

Copper is a transition element but aluminium is not. Aluminium has a lower melting point and boiling point than copper. Suggest one other difference between the physical properties of these two metals.

Suggest one difference between the chemical properties of these two metals.

Copper is used to make the alloy brass. Name the main element mixed with copper to make brass.

Brass is harder than pure copper. Explain why. Use ideas about structure and bonding.

Aluminium is used to manufacture food containers because of its resistance to corrosion. Explain why aluminium is resistant to corrosion.

State one other use for aluminium and explain why aluminium is suitable for this use. use .................................................................................................................... explanation ........................................................................................................................ ...........................................................................................................................................

Aluminium is manufactured by the electrolysis of purified bauxite mixed with cryolite. Carbon electrodes are used. Explain why cryolite is added to the purified bauxite.

Explain why the carbon anodes need to be regularly replaced.

Draw the structure of poly(chloroethene).

There is an accumulation of plastics such as poly(chloroethene) in the oceans. Suggest two properties of poly(chloroethene) that explain this accumulation. 1 ................................................................................................................................ 2 ................................................................................................................................

Burning is used for the disposal of some plastics. This method of disposal causes environmental challenges. One of these challenges is the production of greenhouse gases. Name a greenhouse gas produced by burning plastics.

Another environmental challenge is the production of toxic gases. Name one toxic gas produced during the burning of plastics.

Phosgene, ${\mathrm{C}\mathrm{O}\mathrm{C}\mathrm{l}}_2$, decomposes when heated strongly. Show that the enthalpy change for the reaction is $+101\mathrm{k}\mathrm{J}\mathrm{/}\mathrm{m}\mathrm{o}\mathrm{l}$. Use the bond energies shown in Table 7.1. Table 7.1

Vinegar is an aqueous solution containing ethanoic acid. During the production of vinegar, ethanoic acid is formed from ethanol. Water is also formed as a product. Describe the formation of ethanoic acid from ethanol during the production of vinegar. Include a symbol equation for the formation of ethanoic acid from ethanol and the conditions for the production of vinegar.

Draw the displayed formula of butanoic acid.

Ethyl ethanoate is a structural isomer of butanoic acid. State the meaning of the term structural isomer.

Propanoic acid reacts with butan-1-ol to make an ester. Name the ester made in this reaction.

Draw the structural formula of the ester made in this reaction.

State one condition needed for this esterification reaction.

Deduce the molecular formula of an unbranched carboxylic acid that has only eight carbon atoms in its molecule and no other functional groups.