O Level Chemistry 5070 Paper 21, May/June 2023

is a solid made during the thermal decomposition of limestone in the blast furnace

reacts with both acids and alkalis

has a giant covalent structure

has an ion with an oxidation number of +2

turns white anhydrous copper(II) sulfate blue

is made during the fermentation of aqueous glucose to make ethanol.

State two physical properties of lithium. 1 ................................................................................................................................................ 2 ................................................................................................................................................

Potassium reacts with cold water. The ionic equation for the reaction is shown. $$2\mathrm{K}(\mathrm{s})+2{\mathrm{H}}_2\mathrm{O}(\mathrm{l})\to 2{\mathrm{K}}^{+}(\mathrm{a}\mathrm{q})+2\mathrm{O}{\mathrm{H}}^{-}(\mathrm{a}\mathrm{q})+{\mathrm{H}}_2(\mathrm{g})$$ State, in terms of electrons, why potassium is a reducing agent in this reaction.

State the oxidation number of hydrogen in ${\mathrm{H}}_2$.

Describe what is observed during this reaction.

A sample of sodium chloride is tested using a flame test. State the colour of the flame seen in this test.

Zinc chloride is a soluble salt. It is prepared by the reaction of an insoluble base with a dilute acid. The equation for this reaction is shown. $$\mathrm{Z}\mathrm{n}\mathrm{O}(\mathrm{s})+2\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})\to \mathrm{Z}\mathrm{n}\mathrm{C}{\mathrm{l}}_2(\mathrm{a}\mathrm{q})+{\mathrm{H}}_2\mathrm{O}(\mathrm{l})$$ A sample of $3.50\mathrm{g}$ of zinc oxide is added to $50.0\mathrm{c}{\mathrm{m}}^3$ of $1.20\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}{\mathrm{m}}^3$ hydrochloric acid. Show by calculation that the zinc oxide is in excess.

State why it is important to use an excess of zinc oxide in this preparation.

Suggest how the excess zinc oxide is removed from the reaction mixture to leave only aqueous zinc chloride.

Barium sulfate is an insoluble salt. It is prepared using a precipitation reaction. Name two aqueous solutions that react together to give a barium sulfate precipitate. ................................................................... and ..................................................................

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

Name the experimental technique used to make neutral aqueous sodium nitrate.

The formula for a phosphide ion can be written as ${}_{15}^{31}{\mathrm{P}}^{3-}$. Complete Table 4.1 to show the number of particles in this phosphide ion. Table 4.1

State why the formula for a phosphide ion is ${\mathrm{P}}^{3-}$ rather than ${\mathrm{P}}^{2-}$ or ${\mathrm{P}}^{4-}$.

The formula for a calcium ion is ${\mathrm{C}\mathrm{a}}^{2+}$. Deduce the formula for calcium phosphide.

Calcium phosphate, $\mathrm{C}{\mathrm{a}}_3(\mathrm{P}{\mathrm{O}}_4{)}_2$, is an ionic compound. Explain why calcium phosphate has a high melting point.

Calculate the percentage by mass of phosphorus in calcium phosphate. Give your answer to two significant figures. percentage by mass .........................................................

An equilibrium mixture is formed when the reversible reaction happens in a closed system. State what is meant by the term equilibrium. Include ideas about rate of reaction and the concentrations of the reactant and products in your answer.

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

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

Predict what happens to the rate of the backward reaction when the temperature is increased 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 ...............................................................................................................................

Methane reacts with chlorine to make chloromethane. The reaction is exothermic. $$\mathrm{C}{\mathrm{H}}_4(\mathrm{g})+\mathrm{C}{\mathrm{l}}_2(\mathrm{g})\to \mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{l}(\mathrm{g})+\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{g})$$ Draw, on the axes provided in Fig. 6.1, the reaction pathway diagram for this reaction. Include labels for the: • axes • reactants • products • enthalpy change of reaction, $\mathrm{\Delta }H$ • activation energy, $E_{\mathrm{a}}$.

Hydrogen iodide decomposes to make hydrogen and iodine. $$2\mathrm{H}-\mathrm{I}\to \mathrm{H}-\mathrm{H}+\mathrm{I}-\mathrm{I}$$ 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 alcohols.

Propan-1-ol and propan-2-ol have the same molecular formula but different structural formulae. State the name given to compounds that have the same molecular formula but different structural formulae.

Draw the structural formula for propan-2-ol.

State why propan-1-ol is a saturated compound.

State why propan-1-ol is not a hydrocarbon.

Propan-1-ol reacts in the same way as ethanol. Draw the displayed formula of the product of the reaction of propan-1-ol with acidified aqueous potassium manganate(VII).

Draw the displayed formula of the product of the reaction of propan-1-ol with ethanoic acid in the presence of a catalyst.

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

State why methanol does not conduct electricity.

Methanol is used as a solvent. State the meaning of the term solvent.

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

The electrolysis of aqueous copper(II) sulfate gives different products when copper electrodes are used instead of graphite electrodes. Describe the observations during the electrolysis with copper electrodes.

Magnesium is manufactured by the electrolysis of molten magnesium chloride. At the anode, chloride ions react to make chlorine molecules. Construct the ionic half-equation for this electrode reaction.

Calculate the number of molecules of nitrogen monoxide in $960\mathrm{d}{\mathrm{m}}^3$ of exhaust gas at room temperature and pressure. One mole of any gas contains $6.02\times {10}^{23}$ molecules. number of molecules .........................................................

Nitrogen and oxygen react to make nitrogen monoxide inside a car engine. Construct the equation for this reaction.

State one adverse effect of oxides of nitrogen as pollutants in the air.

Describe how oxides of nitrogen formed in a car engine are removed by a catalytic converter.

The rate of diffusion of nitrogen dioxide, $\mathrm{N}{\mathrm{O}}_2(\mathrm{g})$, is less than that of nitrogen monoxide, $\mathrm{N}\mathrm{O}(\mathrm{g})$, under the same conditions of temperature and pressure. Explain why the rate of diffusion of $\mathrm{N}{\mathrm{O}}_2(\mathrm{g})$ is less than that of $\mathrm{N}\mathrm{O}(\mathrm{g})$ under the same conditions.

The rate of diffusion of nitrogen monoxide decreases as the temperature decreases. Suggest why using ideas about kinetic particle theory.

The diagram in Fig. 10.1 shows the structure of PVC. Draw the structure of the monomer used to make PVC.

Poly(propene) is a polymer used to make plastic food containers. The diagram in Fig. 10.2 shows the structure of poly(propene). Some waste poly(propene) plastic is disposed of by burning. This makes a toxic gas because of incomplete combustion. Name this toxic gas.

State one other environmental challenge caused by the disposal of waste poly(propene) plastic. Explain how this challenge is related to the properties of poly(propene). environmental challenge ................................................................................................... ........................................................................................................................................... explanation ........................................................................................................................ ...........................................................................................................................................

Name one condensation polymer. Draw the displayed formula of the linkage between the repeat units in this polymer. name ......................................................................................................................................... linkage