O Level Chemistry 5070 Paper 22, Oct/Nov 2023

is a waste gas from digestion in animals

turns blue cobalt(II) chloride pink

reacts with ethene above 100 °C to produce ethanol

is a product of photosynthesis

contains an anion with a charge of –2.

Chromium is a transition element. Sodium is an element in Group I of the Periodic Table. State two physical properties of chromium that are different to those of sodium. 1 ................................................................................................................................................ 2 ................................................................................................................................................

Deduce the number of protons and neutrons in the chromium atom shown. ${}_{24}^{53}\mathrm{C}\mathrm{r}$ number of protons .................................................................................................................... number of neutrons ..................................................................................................................

Chromium(III) oxide, ${\mathrm{C}\mathrm{r}}_2{\mathrm{O}}_3$, reacts with carbon and chlorine to produce chromium(III) chloride, ${\mathrm{C}\mathrm{r}\mathrm{C}\mathrm{l}}_3$, and carbon monoxide. Construct the symbol equation for this reaction.

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

Table 2.1 shows the observations made when four different metals are heated in oxygen. Table 2.1

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

Aluminium is used in food containers and overhead electrical cables because it is resistant to corrosion. Explain why aluminium is resistant to corrosion.

State two other reasons why aluminium is used in overhead electrical cables. 1 ........................................................................................................................................ 2 ........................................................................................................................................

Complete the equation for this reaction by adding state symbols. $${\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3(\dots \dots )+2\mathrm{H}\mathrm{C}\mathrm{l}(\dots \dots )\to {\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{l}}_2(\mathrm{a}\mathrm{q})+{\mathrm{H}}_2\mathrm{O}(\dots \dots )+{\mathrm{C}\mathrm{O}}_2(\mathrm{g})$$

Fig. 3.1 shows the volume of carbon dioxide gas released as the reaction proceeds. Deduce the volume of carbon dioxide gas released after 40 seconds. volume .................................................. ${\mathrm{c}\mathrm{m}}^3$

The student repeats the experiment using the same mass of smaller pieces of calcium carbonate. All other conditions stay the same. Draw a line on the grid in Fig. 3.1 to show how the volume of carbon dioxide changes when smaller pieces of calcium carbonate are used.

The student repeats the experiment at 20 °C. All other conditions stay the same. Describe and explain, using collision theory, how the rate of reaction differs when a temperature of 20 °C is used.

A sample of carbon dioxide 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 increasing the pressure in the gas syringe decreases the volume of gas when the temperature stays the same.

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

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

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

Iodide ions reduce manganese(IV) oxide, ${\mathrm{M}\mathrm{n}\mathrm{O}}_2$, to ${\mathrm{M}\mathrm{n}}^{2+}$ ions. $$2{\mathrm{I}}^{-}+{\mathrm{M}\mathrm{n}\mathrm{O}}_2+4{\mathrm{H}}^{+}\to {\mathrm{M}\mathrm{n}}^{2+}+{\mathrm{I}}_2+2{\mathrm{H}}_2\mathrm{O}$$ Explain, in terms of movement of electrons, how iodide ions act as a reducing agent in this reaction.

State the name of the type of reaction that involves simultaneous oxidation and reduction.

Phosphorus(III) iodide is produced when phosphorus reacts with iodine. Complete Fig. 4.1 to show the dot-and-cross diagram for a molecule of phosphorus(III) iodide. Show only the outer shell electrons.

Fig. 5.1 shows the displayed formula of compound A. On Fig. 5.1, draw a circle around the functional group that reacts with aqueous bromine.

Describe the colour change when excess compound A is added to a few drops of aqueous bromine in a test tube. colour of aqueous bromine ................................................................................................ colour after addition of compound A .................................................................................

Deduce the molecular formula of compound A.

Compound A is a liquid at room temperature. Describe the motion and separation of the particles in a liquid. motion ............................................................................................................................... separation .........................................................................................................................

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

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

Steam reacts with carbon to produce carbon monoxide and hydrogen. $$\text{steam}+\text{carbon}\rightleftharpoons \text{carbon monoxide}+\text{hydrogen}$$ The forward reaction is endothermic. Explain, in terms of bond making and bond breaking, why this reaction is endothermic.

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 endothermic enthalpy change.

Carbon monoxide, water and carbon dioxide are formed during the incomplete combustion of carbon-containing fuels. Name one other substance formed during the incomplete combustion of carbon-containing fuels.

State one adverse effect of carbon monoxide.

Hydrogen is used in a hydrogen-oxygen fuel cell. Describe two advantages of a hydrogen-oxygen fuel cell compared with a gasoline/petrol engine. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................

Dilute hydrochloric acid reacts with aqueous sodium carbonate. $$2\mathrm{H}\mathrm{C}\mathrm{l}+{\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3\to 2\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{C}\mathrm{O}}_2$$ A student titrates $20.0{\mathrm{c}\mathrm{m}}^3$ of $0.0250{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ aqueous sodium carbonate with dilute hydrochloric acid using methyl orange as an indicator. A volume of $15.5{\mathrm{c}\mathrm{m}}^3$ of dilute hydrochloric acid reacts exactly with the $0.0250{\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$ aqueous sodium carbonate. Calculate the concentration, in ${\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$, of the dilute hydrochloric acid. concentration of dilute hydrochloric acid .......................................... ${\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{/}\mathrm{d}\mathrm{m}}^3$

State the colour of methyl orange in alkaline solution.

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

Calculate the volume, measured at r.t.p., of carbon dioxide produced, in ${\mathrm{c}\mathrm{m}}^3$, when $2.65\mathrm{g}$ of sodium carbonate reacts with excess hydrochloric acid. $$2\mathrm{H}\mathrm{C}\mathrm{l}+{\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3\to 2\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{C}\mathrm{O}}_2$$ volume of carbon dioxide .................................................. ${\mathrm{c}\mathrm{m}}^3$

Hydrochloric acid is a strong acid. Define the term strong in the phrase strong acid.

Oxides of nitrogen contribute to acid rain. State one other adverse effect of oxides of nitrogen.

Oxides of nitrogen are removed from car exhausts by catalytic converters. Complete the symbol equation for the reaction that occurs in catalytic converters. $$2\mathrm{C}\mathrm{O}+2\mathrm{N}\mathrm{O}\to \dots \dots \dots \dots \dots \dots \dots \cdots +\dots \dots \dots \dots \dots \dots \dots \dots$$

The equation for the reaction of carbon monoxide with hydrogen at a high temperature in a closed container is shown. $$\mathrm{C}\mathrm{O}(\mathrm{g})+2{\mathrm{H}}_2(\mathrm{g})\rightleftharpoons {\mathrm{C}\mathrm{H}}_3\mathrm{O}\mathrm{H}(\mathrm{g})$$ methanol The forward reaction is exothermic. Predict and explain the effect, if any, on the position of equilibrium when the pressure is increased and the temperature remains constant.

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

Methanol reacts with ethanoic acid, ${\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$, to produce an ester. Name the ester and draw its displayed formula. name ......................................................................................................................................... displayed formula

Methanol is a member of the alcohol homologous series. Describe two general characteristics of a homologous series. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................

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 diamond and iodine

the difference in the electrical conductivities of calcium and iodine.

Diamond and graphite are different forms of carbon. Explain, in terms of its structure, why graphite is a lubricant.

A compound of sodium, iodine and oxygen contains 11.62% sodium, 64.14% iodine and 24.24% oxygen by mass. Deduce the empirical formula of this compound. empirical formula ..........................................................