O Level Chemistry 5070 Paper 21, Oct/Nov 2023

is a toxic gas produced by the incomplete combustion of carbon-containing compounds

turns anhydrous copper(II) sulfate blue

leads to deoxygenation of water in rivers

in aqueous solution, gives a white precipitate on addition of acidified aqueous barium chloride

contains an anion with a charge of –1.

Potassium is an element in Group I of the Periodic Table. Copper is a transition element. State two physical properties of potassium that are different from those of copper.

Complete the diagram in Fig. 2.1 to show the electronic configuration of a potassium ion. Include the charge on the ion.

Table 2.1 shows the observations when four different metals react with cold water. Table 2.1

Put the four metals in order of their reactivity. Put the least reactive metal first.

Deduce the number of protons and neutrons in the copper atom shown. ${}_{29}^{65}\mathrm{C}\mathrm{u}$ number of protons .................................................................................................................... number of neutrons ..................................................................................................................

In the presence of oxygen, copper reacts with sulfuric acid, ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$, to form copper(II) sulfate and water. Construct the symbol equation for this reaction.

Copper can be used as a catalyst. State how a catalyst increases the rate of a chemical reaction.

Name the catalyst used in the Contact process.

Give two reasons why copper is used in electrical wiring.

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

Fig. 3.1 shows the volume of hydrogen released as the reaction proceeds. Deduce the time taken from the beginning of the experiment to collect $39{\mathrm{c}\mathrm{m}}^3$ of hydrogen.

The student repeats the experiment using dilute hydrochloric acid with a higher concentration. All other conditions stay the same. Draw a line on the grid in Fig. 3.1 to show how the volume of hydrogen changes when dilute hydrochloric acid with a higher concentration is used.

The student repeats the experiment at 30°C. All other conditions stay the same. Describe and explain, using collision theory, how the rate of reaction differs when a temperature of 30°C is used.

A sample of hydrogen is put into a gas syringe. The end of the gas syringe is then blocked so that no gas can escape. Explain, using kinetic particle theory, why decreasing the pressure in the gas syringe increases the volume of gas when the temperature stays the same.

Concentrated aqueous calcium bromide is electrolysed using graphite electrodes. Predict the product at each electrode. anode ........................................................................................................................................ cathode .....................................................................................................................................

Molten calcium bromide is electrolysed using graphite electrodes. Construct the ionic half-equation for the reaction at each electrode when molten calcium bromide is electrolysed. anode ........................................................................................................................................ cathode .....................................................................................................................................

Describe a test for aqueous bromide ions. Include the observations for a positive result. test ............................................................................................................................................ observations .............................................................................................................................

Calcium reduces zinc ions to zinc. $$\mathrm{C}\mathrm{a}+{\mathrm{Z}\mathrm{n}}^{2+}\to \mathrm{Z}\mathrm{n}+{\mathrm{C}\mathrm{a}}^{2+}$$ Explain, in terms of the movement of electrons, how calcium acts as a reducing agent in this equation.

State the oxidation number of the ${\mathrm{Z}\mathrm{n}}^{2+}$ ion.

Sulfur dibromide is produced when sulfur reacts with bromine. Complete Fig. 4.1 to show the dot-and-cross diagram for a molecule of sulfur dibromide. Show only the outer shell electrons.

Fig. 5.1 shows the displayed formula of compound A. Draw a circle around the functional group on Fig. 5.1 that is also present in alkenes.

Deduce the molecular formula of compound A.

Compound A is a solid at 20°C. Describe the motion and arrangement of the particles in a solid. motion ............................................................................................................................... arrangement ......................................................................................................................

Alkenes react with hydrogen in the presence of a catalyst. Draw a circle around the type of reaction that takes place. addition condensation neutralisation substitution

Name the catalyst used.

Fig. 5.2 shows the structure of compound B. Compound B can be polymerised. Draw two repeat units of the polymer formed when compound B is polymerised.

Fig. 5.3 shows part of the structure of a protein. Name the type of monomer used to make proteins.

Name the linkage in proteins.

The nitrogen for this process comes from the air. State the percentage by volume of nitrogen in clean, dry air.

State a source of hydrogen for the Haber process.

The forward reaction in the Haber process is exothermic. Explain, in terms of bond making and bond breaking, why this reaction is exothermic.

The transfer of thermal energy in a chemical reaction is called the enthalpy change. Write the symbol for an enthalpy change. Include the sign for an exothermic enthalpy change.

Aqueous ammonia is an alkali. Aqueous ammonia reacts with dilute nitric acid to form a salt. Name this salt.

Name the experimental technique used to make a solution of this salt from dilute nitric acid and aqueous ammonia.

Dilute ethanoic acid reacts with aqueous calcium hydroxide. $$2{\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}+{\mathrm{C}\mathrm{a}(\mathrm{O}\mathrm{H})}_2\to ({\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}{)}_2\mathrm{C}\mathrm{a}+2{\mathrm{H}}_2\mathrm{O}$$ A student reacts $25.0{\mathrm{c}\mathrm{m}}^3$ of $0.0100{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ aqueous calcium hydroxide with dilute ethanoic acid using thymolphthalein as an indicator. A volume of $12.5{\mathrm{c}\mathrm{m}}^3$ of dilute ethanoic acid reacts exactly with the $0.0100{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ aqueous calcium hydroxide. Calculate the concentration, in ${\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$, of the dilute ethanoic acid.

State the colour of thymolphthalein in aqueous calcium hydroxide.

Ethanoic acid is a weak acid. Define the term weak in the phrase weak acid.

Write the formula of the ion present in aqueous solutions of acids.

Dilute ethanoic acid reacts with sodium carbonate. $$2{\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}+{\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3\to 2{\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{N}\mathrm{a}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{C}\mathrm{O}}_2$$ Calculate the volume, measured at r.t.p., of carbon dioxide produced, in ${\mathrm{c}\mathrm{m}}^3$, when $3.18\mathrm{g}$ of sodium carbonate reacts with excess dilute ethanoic acid.

Sulfur dioxide contributes to acid rain. State one source of sulfur dioxide in the air.

Describe one method of reducing the amount of sulfur dioxide getting into the air.

In the Contact process, sulfur dioxide reacts with oxygen. Complete the symbol equation for this reaction. $$2{\mathrm{S}\mathrm{O}}_2+{\mathrm{O}}_2\rightleftharpoons \dots \dots \dots \dots \dots \dots \dots \dots$$

Ethanoic acid is manufactured from methanol. $${\mathrm{C}\mathrm{H}}_3\mathrm{O}\mathrm{H}(\mathrm{g})+\mathrm{C}\mathrm{O}(\mathrm{g})\rightleftharpoons {\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}(\mathrm{g})$$ The forward reaction is exothermic. Predict and explain the effect, if any, on the position of equilibrium when the pressure is decreased and the temperature remains constant.

Predict and explain the effect, if any, on the position of equilibrium when the temperature is decreased and the pressure remains constant.

Ethanoic acid can be produced by bacterial oxidation. Describe one other method of making ethanoic acid by oxidising an alcohol other than methanol. name of alcohol ........................................................................................................................ name of oxidising agent ............................................................................................................

Ethanoic acid reacts with propan-1-ol, ${\mathrm{C}\mathrm{H}}_3{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{O}\mathrm{H}$, to produce an ester. Name the ester and draw its displayed formula. name ......................................................................................................................................... displayed formula

Table 9.1 shows the melting points and relative electrical conductivities of three elements. Table 9.1

Use ideas about structure and bonding to explain: the difference in the melting points of magnesium and phosphorus

the difference in the electrical conductivities of graphite and phosphorus.

Diamond and graphite are different forms of carbon. Explain, in terms of its structure and bonding, why diamond is used in cutting tools.

A compound of phosphorus, oxygen and chlorine contains 20.2% phosphorus, 10.4% oxygen and 69.4% chlorine by mass. Deduce the empirical formula of this compound.