O Level Chemistry 5070 Paper 22, May/June 2023

is neutral

reacts with calcium oxide to form slag in the blast furnace

reacts with warm dilute hydrochloric acid to give a blue coloured solution

is amphoteric

contains an ion with an oxidation number of +3

decolourises acidified aqueous potassium manganate(VII).

Chlorine is a green gas at room temperature and pressure. State the appearance of iodine at room temperature and pressure.

Chlorine reacts with aqueous potassium iodide in a displacement reaction. $${\mathrm{C}\mathrm{l}}_2(\mathrm{a}\mathrm{q})+2{\mathrm{I}}^{-}(\mathrm{a}\mathrm{q})\to 2{\mathrm{C}\mathrm{l}}^{-}(\mathrm{a}\mathrm{q})+{\mathrm{I}}_2(\mathrm{a}\mathrm{q})$$ Explain, in terms of electrons, why chlorine is an oxidising agent in this reaction.

State the oxidation number of iodine in ${\mathrm{I}}_2$.

Describe what is observed during the displacement reaction.

The rate of diffusion of fluorine gas is greater than that of chlorine gas under the same conditions of temperature and pressure. State what is meant by the term diffusion.

Explain why the rate of diffusion of fluorine is greater than that of chlorine under the same conditions.

The rate of diffusion of fluorine increases as the temperature increases. Suggest why using ideas about kinetic particle theory.

Zinc nitrate is a soluble salt. It is prepared by the reaction of an insoluble carbonate with a dilute acid. The equation for this reaction is shown. $${\mathrm{Z}\mathrm{n}\mathrm{C}\mathrm{O}}_3(\mathrm{s})+2{\mathrm{H}\mathrm{N}\mathrm{O}}_3(\mathrm{a}\mathrm{q})\to \mathrm{Z}\mathrm{n}({\mathrm{N}\mathrm{O}}_3{)}_2(\mathrm{a}\mathrm{q})+{\mathrm{H}}_2\mathrm{O}(\mathrm{l})+{\mathrm{C}\mathrm{O}}_2(\mathrm{g})$$ A sample of $4.50\mathrm{g}$ of zinc carbonate is added to $50.0{\mathrm{c}\mathrm{m}}^3$ of $1.30\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}{\mathrm{d}\mathrm{m}}^3$ nitric acid. Show by calculation that the zinc carbonate is in excess.

Once the reaction has finished the mixture is filtered. State why the mixture is filtered.

Describe how to make pure, dry zinc nitrate crystals from an aqueous solution of zinc nitrate.

Lead chloride is an insoluble salt. It is prepared using a precipitation reaction. Name two aqueous solutions that react together to give a precipitate of lead chloride.

Ammonium sulfate is a soluble salt. It is prepared by the reaction of an alkali and an acid. Name the alkali and the acid used. alkali ................................................................ acid ..................................................................

The formula for a nitride ion can be written as ${}_7^{15}{\mathrm{N}}^{3-}$. Complete Table 4.1 to show the number of particles in this nitride ion. Table 4.1

State why the formula for a magnesium ion is ${\mathrm{M}\mathrm{g}}^{2+}$ rather than ${\mathrm{M}\mathrm{g}}^{+}$ or ${\mathrm{M}\mathrm{g}}^{3+}$.

The formula for a nitride ion is ${\mathrm{N}}^{3-}$. Deduce the formula for magnesium nitride.

Magnesium nitrate, $\mathrm{M}\mathrm{g}({\mathrm{N}\mathrm{O}}_3{)}_2$, is an ionic compound. Predict two physical properties of magnesium nitrate. 1 ................................................................................................................................................ 2 ................................................................................................................................................

Calculate the percentage by mass of nitrogen in magnesium nitrate. Give your answer to two significant figures. percentage by mass .........................................................

An equilibrium mixture is formed when the reversible reaction happens in a closed system. Explain why the reversible reaction must be in a closed system for an equilibrium mixture to be formed.

Predict what happens to the position of equilibrium when the temperature is decreased and the pressure remains constant. Explain your answer. prediction ........................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................

Predict what happens to the position of equilibrium when the pressure is decreased and the temperature remains constant. Explain your answer. prediction ........................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................

Predict what happens to the rate of the backward reaction when the temperature is decreased and the pressure remains constant. Explain your answer. prediction .................................................................................................................................. explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

Predict what happens to the rate of the backward reaction when the pressure is increased and the temperature remains constant. Explain your answer. prediction .................................................................................................................................. explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

Nitrogen reacts with oxygen to make nitrogen monoxide. The reaction is endothermic. $${\mathrm{N}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\to 2\mathrm{N}\mathrm{O}(\mathrm{g})$$ Draw, on the axes provided in Fig. 6.1, the reaction pathway diagram for this reaction. Include labels for the: • axes • reactants • product • enthalpy change of reaction, $\mathrm{\Delta }H$ • activation energy, $E_{\mathrm{a}}$.

Hydrogen reacts with bromine to make hydrogen bromide. $$\mathrm{H}-\mathrm{H}+\mathrm{B}\mathrm{r}-\mathrm{B}\mathrm{r}\to 2\mathrm{H}-\mathrm{B}\mathrm{r}$$ Calculate the enthalpy change of this reaction. Use the bond energies in Table 6.1. Table 6.1

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

State the general formula of the homologous series of alkenes.

But-1-ene and but-2-ene are structural isomers. State the meaning of the term structural isomers.

Draw the displayed formula for but-2-ene.

But-1-ene is an unsaturated hydrocarbon. State why but-1-ene is an unsaturated compound.

State why but-1-ene is a hydrocarbon.

But-1-ene reacts with steam in the presence of a catalyst and reacts with bromine. Draw the structural formula of the product of the reaction with steam in the presence of a catalyst.

Draw the structural formula of the product of the reaction with bromine.

Ethene is a covalent substance. Draw a dot-and-cross diagram to show the bonding in a molecule of ethene. Include only the outer shell electrons of each atom.

Explain why ethene has a low melting point.

The table shows some information about the electrolysis of three different electrolytes using graphite electrodes. Complete Table 8.1 with the names of the products at each electrode. Table 8.1

Give two reasons why graphite is a suitable material from which to make electrodes. 1 ................................................................................................................................................ 2 ................................................................................................................................................

Aluminium is manufactured by the electrolysis of aluminium oxide dissolved in molten cryolite. At the anode, oxide ions react to make oxygen molecules. Construct the ionic half-equation for this electrode reaction.

Calculate the number of molecules of carbon dioxide in $480{\mathrm{d}\mathrm{m}}^3$ of clean, dry air at room temperature and pressure. One mole of any gas contains $6.02\times {10}^{23}$ molecules. number of molecules .........................................................

Complete combustion of fuels such as gasoline makes carbon dioxide. One of the hydrocarbons in gasoline has the molecular formula ${\mathrm{C}}_9{\mathrm{H}}_{20}$. Construct the equation for the complete combustion of ${\mathrm{C}}_9{\mathrm{H}}_{20}$.

Higher levels of atmospheric carbon dioxide lead to increased global warming. Give one adverse effect of global warming.

Describe how the presence of gases such as carbon dioxide in the atmosphere causes global warming.

Carbon dioxide is removed from the atmosphere by photosynthesis. State the word equation for photosynthesis.

The diagram in Fig. 10.1 shows the structure of a section of a protein. Draw the general structure of the amino acid monomers used to make proteins.

Proteins are polyamides. Name one other polyamide.

PET is a polymer used to make plastic bottles. The diagram in Fig. 10.2 shows the structure of PET. Name the linkage present in PET.

Proteins and PET are both made by condensation polymerisation. Describe the differences between condensation polymerisation and addition polymerisation.

Describe two environmental challenges caused by the disposal of plastics such as PET. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................