Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2023 Winter Zone 1

1. A list of gases is shown: ammonia, carbon dioxide, carbon monoxide, ethene, fluorine, oxygen, sulfur dioxide, xenon. Answer the following questions using only the gases from the list. Each gas may be used once, more than once or not at all.
(a) Give the name of the gas that causes acid rain. [1]
(b) Give the name of the gas that forms an alkaline solution when dissolved in water. [1]
(c) Give the name of the gas that is inert. [1]
(d) Give the name of the gas that is a product of photosynthesis. [1]
(e) Give the name of the gas that can form a polymer. [1]
(f) Give the name of the gas that is produced in the test for nitrate ions. [1]

1. A list of gases is shown: ammonia, carbon dioxide, carbon monoxide, ethene, fluorine, oxygen, sulfur dioxide, xenon. Answer the following questions using only the gases from the list. Each gas may be used once, more than once or not at all.
(a) Give the name of the gas that causes acid rain. [1]
(b) Give the name of the gas that forms an alkaline solution when dissolved in water. [1]
(c) Give the name of the gas that is inert. [1]
(d) Give the name of the gas that is a product of photosynthesis. [1]
(e) Give the name of the gas that can form a polymer. [1]
(f) Give the name of the gas that is produced in the test for nitrate ions. [1]

2. Boron and aluminium are Group III elements.
(a) Boron has only two naturally occurring isotopes, $^{10}B$ and $^{11}B$. Complete Table 2.1 to show the numbers of protons, neutrons and electrons in an atom of $^{11}B$.
Table 2.1
| number of protons | number of neutrons | number of electrons |
[2]
(b) The relative atomic mass of boron to one decimal place is 10.8.
(i) Determine the relative abundance of $^{10}B$ present in boron. Give your answer as a percentage. [1]
(ii) Use the relative atomic mass of boron to calculate the number of atoms in 0.540 g of boron. Give your answer in standard form. [2]
(c) Aluminium is extracted from its purified ore as shown in Fig. 2.1.
(i) Name the ore of aluminium. [1]
(ii) The electrolyte contains aluminium oxide and one other substance. Name the other substance and explain why it is used. [2]
(iii) Write the ionic half-equation for the reaction at the cathode. [2]
(iv) Explain why the anodes need frequent replacement. [2]
(d) State two physical properties of aluminium that make it suitable for use in overhead electrical cables. [2]
(e) Explain the apparent unreactivity of aluminium. [2]
(f) Aluminium reacts with fluorine to form aluminium fluoride, AlF3, an ionic compound.
(i) Write the symbol equation for this reaction. [2]
(ii) Complete Fig. 2.2 to show the electronic configuration of one aluminium ion and one fluoride ion. Show the charges on the ions. [3]

2. Boron and aluminium are Group III elements.
(a) Boron has only two naturally occurring isotopes, $^{10}B$ and $^{11}B$. Complete Table 2.1 to show the numbers of protons, neutrons and electrons in an atom of $^{11}B$.
Table 2.1
| number of protons | number of neutrons | number of electrons |
[2]
(b) The relative atomic mass of boron to one decimal place is 10.8.
(i) Determine the relative abundance of $^{10}B$ present in boron. Give your answer as a percentage. [1]
(ii) Use the relative atomic mass of boron to calculate the number of atoms in 0.540 g of boron. Give your answer in standard form. [2]
(c) Aluminium is extracted from its purified ore as shown in Fig. 2.1.
(i) Name the ore of aluminium. [1]
(ii) The electrolyte contains aluminium oxide and one other substance. Name the other substance and explain why it is used. [2]
(iii) Write the ionic half-equation for the reaction at the cathode. [2]
(iv) Explain why the anodes need frequent replacement. [2]
(d) State two physical properties of aluminium that make it suitable for use in overhead electrical cables. [2]
(e) Explain the apparent unreactivity of aluminium. [2]
(f) Aluminium reacts with fluorine to form aluminium fluoride, AlF3, an ionic compound.
(i) Write the symbol equation for this reaction. [2]
(ii) Complete Fig. 2.2 to show the electronic configuration of one aluminium ion and one fluoride ion. Show the charges on the ions. [3]

3. Order of reactivity can be determined by displacement reactions.
(a) A student investigates the reactivities of four metals by carrying out a series of experiments. Each of the metals lead, manganese, silver and zinc are added separately to aqueous metal nitrates of the other metals.
(i) Table 3.1 shows some of the results. [Table_1] Complete Table 3.1 and place the four metals in their order of reactivity with the most reactive first. [3]
(ii) Suggest why the metal nitrates and not the metal sulfates of these four metals are used as the aqueous solutions. [1]
(iii) Write the symbol equation for the reaction between zinc and silver nitrate. [2]
(b) The reactivity of Group VII elements can be investigated experimentally. A student bubbles chlorine gas into a test-tube containing aqueous potassium bromide.
(i) Describe the colour change seen in the test-tube. [2]
(ii) Complete the ionic equation for this reaction. Include state symbols. [3]
(iii) The reactivity trend seen in Cl, Br and I applies to all the elements in Group VII. Use the Periodic Table to identify the Group VII element which cannot displace any other Group VII elements. [1]

3. Order of reactivity can be determined by displacement reactions.
(a) A student investigates the reactivities of four metals by carrying out a series of experiments. Each of the metals lead, manganese, silver and zinc are added separately to aqueous metal nitrates of the other metals.
(i) Table 3.1 shows some of the results. [Table_1] Complete Table 3.1 and place the four metals in their order of reactivity with the most reactive first. [3]
(ii) Suggest why the metal nitrates and not the metal sulfates of these four metals are used as the aqueous solutions. [1]
(iii) Write the symbol equation for the reaction between zinc and silver nitrate. [2]
(b) The reactivity of Group VII elements can be investigated experimentally. A student bubbles chlorine gas into a test-tube containing aqueous potassium bromide.
(i) Describe the colour change seen in the test-tube. [2]
(ii) Complete the ionic equation for this reaction. Include state symbols. [3]
(iii) The reactivity trend seen in Cl, Br and I applies to all the elements in Group VII. Use the Periodic Table to identify the Group VII element which cannot displace any other Group VII elements. [1]

4. Aqueous hydrogen peroxide, $H_2O_2$, slowly forms water and oxygen at room temperature and pressure, r.t.p. This reaction is catalysed by manganese(IV) oxide. The equation is shown.
$2H_2O_2(aq) \rightarrow 2H_2O(l) + O_2(g)$
(a) State the test for oxygen gas. [1]
(b) A student investigates the rate of formation of oxygen gas when manganese(IV) oxide is added to aqueous hydrogen peroxide. The volume of oxygen gas formed is measured at regular time intervals at r.t.p.
(i) State how the graph in Fig. 4.1 shows the rate of reaction at time $t_2$, is lower than at time $t_1$. [1]
(ii) Explain, using collision theory, why the rate of reaction at time $t_2$ is lower than at time $t_1$. [2]
(iii) On Fig. 4.1, sketch the graph obtained when the experiment is repeated using aqueous hydrogen peroxide at a higher temperature. All other conditions remain the same. [2]
(c) Manganese(IV) oxide is added to 20 cm$^3$ of aqueous hydrogen peroxide. The total volume of oxygen gas produced is 72 cm$^3$ at r.t.p.
Calculate the concentration of the aqueous hydrogen peroxide in g/dm$^3$ using the following steps:
- Calculate the number of moles of oxygen gas produced.
- Determine the number of moles of hydrogen peroxide which reacts.
- Calculate the concentration of aqueous hydrogen peroxide in mol/dm$^3$.
- Calculate the concentration of aqueous hydrogen peroxide in g/dm$^3$.
[5]
(d) Suggest the identity of one other metal oxide which also catalyses this reaction. [1]

4. Aqueous hydrogen peroxide, $H_2O_2$, slowly forms water and oxygen at room temperature and pressure, r.t.p. This reaction is catalysed by manganese(IV) oxide. The equation is shown.
$2H_2O_2(aq) \rightarrow 2H_2O(l) + O_2(g)$
(a) State the test for oxygen gas. [1]
(b) A student investigates the rate of formation of oxygen gas when manganese(IV) oxide is added to aqueous hydrogen peroxide. The volume of oxygen gas formed is measured at regular time intervals at r.t.p.
(i) State how the graph in Fig. 4.1 shows the rate of reaction at time $t_2$, is lower than at time $t_1$. [1]
(ii) Explain, using collision theory, why the rate of reaction at time $t_2$ is lower than at time $t_1$. [2]
(iii) On Fig. 4.1, sketch the graph obtained when the experiment is repeated using aqueous hydrogen peroxide at a higher temperature. All other conditions remain the same. [2]
(c) Manganese(IV) oxide is added to 20 cm$^3$ of aqueous hydrogen peroxide. The total volume of oxygen gas produced is 72 cm$^3$ at r.t.p.
Calculate the concentration of the aqueous hydrogen peroxide in g/dm$^3$ using the following steps:
- Calculate the number of moles of oxygen gas produced.
- Determine the number of moles of hydrogen peroxide which reacts.
- Calculate the concentration of aqueous hydrogen peroxide in mol/dm$^3$.
- Calculate the concentration of aqueous hydrogen peroxide in g/dm$^3$.
[5]
(d) Suggest the identity of one other metal oxide which also catalyses this reaction. [1]

5. Methane reacts with steam to produce hydrogen gas.
$CH_4(g) + H_2O(g) \rightarrow CO(g) + 3H_2(g)$ ΔH = +200kJ/mol
The reaction takes place at 1000°C and 100kPa pressure.
(a) The reaction is reversible and reaches an equilibrium in a closed system. State two features of an equilibrium. [2]
(b) State and explain, in terms of equilibrium, what happens to the concentration of hydrogen when:
(i) the pressure is increased [2]
(ii) the temperature is increased [2]
(iii) a catalyst is used. [2]
(c) Methane is a greenhouse gas which contributes to global warming.
(i) Name a greenhouse gas found in clean, dry air. [1]
(ii) Explain, in terms of thermal energy, how greenhouse gases cause global warming. [3]

5. Methane reacts with steam to produce hydrogen gas.
$CH_4(g) + H_2O(g) \rightarrow CO(g) + 3H_2(g)$ ΔH = +200kJ/mol
The reaction takes place at 1000°C and 100kPa pressure.
(a) The reaction is reversible and reaches an equilibrium in a closed system. State two features of an equilibrium. [2]
(b) State and explain, in terms of equilibrium, what happens to the concentration of hydrogen when:
(i) the pressure is increased [2]
(ii) the temperature is increased [2]
(iii) a catalyst is used. [2]
(c) Methane is a greenhouse gas which contributes to global warming.
(i) Name a greenhouse gas found in clean, dry air. [1]
(ii) Explain, in terms of thermal energy, how greenhouse gases cause global warming. [3]

6. Ethanol is manufactured by two methods: method 1 fermentation of aqueous glucose, method 2 catalytic addition of steam to an alkene.
(a) Method 1 takes place at room temperature and pressure. State two other conditions needed in method 1. [2]
(b) (i) State the typical temperature and pressure used in method 2. [2]
(ii) Name the alkene used in method 2. [1]
(iii) State why the reaction in method 2 is referred to as an addition reaction. [1]
(c) The catalyst in method 2 is phosphoric acid, $H_3PO_4$. Dilute phosphoric acid is a weak acid which contains phosphate ions, $PO_4^{3-}$.
(i) State what is meant by the term acid. [1]
(ii) State the meaning of weak in the term weak acid. [1]
(iii) Determine the oxidation number of phosphorus in the $PO_4^{3-}$ ion. Show your working. [2]
(d) Give one advantage of each method of production of ethanol. [2]
(e) Ethanol can be converted to ethanoic acid by reacting it with an acidified oxidising agent.
(i) Name the acidified oxidising agent. [1]
(ii) State, in terms of redox, what type of reagent ethanol is in this reaction. [1]
(f) Ethanoic acid reacts with calcium to form a salt and one other product.
(i) Name the salt. [1]
(ii) Write the formula of the salt. [1]
(iii) Identify the other product. [1]

6. Ethanol is manufactured by two methods: method 1 fermentation of aqueous glucose, method 2 catalytic addition of steam to an alkene.
(a) Method 1 takes place at room temperature and pressure. State two other conditions needed in method 1. [2]
(b) (i) State the typical temperature and pressure used in method 2. [2]
(ii) Name the alkene used in method 2. [1]
(iii) State why the reaction in method 2 is referred to as an addition reaction. [1]
(c) The catalyst in method 2 is phosphoric acid, $H_3PO_4$. Dilute phosphoric acid is a weak acid which contains phosphate ions, $PO_4^{3-}$.
(i) State what is meant by the term acid. [1]
(ii) State the meaning of weak in the term weak acid. [1]
(iii) Determine the oxidation number of phosphorus in the $PO_4^{3-}$ ion. Show your working. [2]
(d) Give one advantage of each method of production of ethanol. [2]
(e) Ethanol can be converted to ethanoic acid by reacting it with an acidified oxidising agent.
(i) Name the acidified oxidising agent. [1]
(ii) State, in terms of redox, what type of reagent ethanol is in this reaction. [1]
(f) Ethanoic acid reacts with calcium to form a salt and one other product.
(i) Name the salt. [1]
(ii) Write the formula of the salt. [1]
(iii) Identify the other product. [1]