Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2023 Winter Zone 3

A list of substances is shown: barium nitrate, carbon monoxide, hydrated cobalt(II) chloride, copper(II) oxide, anhydrous copper(II) sulfate, ethane, potassium iodide, propene, sodium bromide, sulfur dioxide, zinc oxide. Answer the following questions using only the substances from the list. Each substance may be used once, more than once or not at all.
(a) Give the name of the substance that gives a lilac colour in a flame test. [1]
(b) Forms a cream precipitate when its aqueous solution reacts with acidified aqueous silver nitrate. [1]
(c) Is an acidic oxide. [1]
(d) Is an unsaturated hydrocarbon. [1]
(e) Is a product of incomplete combustion of fossil fuels. [1]
(f) Is used to test for the presence of water. [1]

A list of substances is shown: barium nitrate, carbon monoxide, hydrated cobalt(II) chloride, copper(II) oxide, anhydrous copper(II) sulfate, ethane, potassium iodide, propene, sodium bromide, sulfur dioxide, zinc oxide. Answer the following questions using only the substances from the list. Each substance may be used once, more than once or not at all.
(a) Give the name of the substance that gives a lilac colour in a flame test. [1]
(b) Forms a cream precipitate when its aqueous solution reacts with acidified aqueous silver nitrate. [1]
(c) Is an acidic oxide. [1]
(d) Is an unsaturated hydrocarbon. [1]
(e) Is a product of incomplete combustion of fossil fuels. [1]
(f) Is used to test for the presence of water. [1]

Table 2.1 gives information about particles A, B, C, D, E and F.
![Table_1]
(a) Give the letters of all the particles which are:
(i) atoms [1]
(ii) ions with a charge of 2– [1]
(iii) cations. [1]
(b) State the atomic number of A. [1]
(c) Determine the number of nucleons in D. [1]
(d) State the electronic configuration of D. [1]
(e) State the group number of F. [1]
(f) State the period number of B. [1]

Table 2.1 gives information about particles A, B, C, D, E and F.
![Table_1]
(a) Give the letters of all the particles which are:
(i) atoms [1]
(ii) ions with a charge of 2– [1]
(iii) cations. [1]
(b) State the atomic number of A. [1]
(c) Determine the number of nucleons in D. [1]
(d) State the electronic configuration of D. [1]
(e) State the group number of F. [1]
(f) State the period number of B. [1]

This question is about nitrogen and some of its compounds.
(a) Nitrogen is converted into ammonia, NH$_3$, in the Haber process.
(i) Nitrogen is obtained from air. State the percentage of nitrogen in clean, dry air. [1]
(ii) State the source of hydrogen for the Haber process. [1]
(iii) Complete the dot-and-cross diagram for a molecule of ammonia. Show the outer shell electrons only. ! [2]
(iv) Write a chemical equation for the reaction occurring in the Haber process and give the typical reaction conditions. Include units where appropriate.
Chemical equation: [5]
(b) Ammonia is converted into nitric acid. The first stage uses a catalyst and occurs at 900°C and 5 atm. $$4NH_3(g) + 5O_2(g) \rightarrow 4NO(g) + 6H_2O(g)$$ The forward reaction is exothermic.
(i) Suggest which element is most likely used as a catalyst: calcium, lead, platinum, sodium, sulfur. [1]
(ii) State the oxidation number of nitrogen in:
NH$_3$. [1]
NO. [1]
(iii) Use your answer to explain whether the nitrogen in ammonia undergoes oxidation or reduction. [1]
(iv) Complete Table 3.1 using increases, decreases or no change. ![Table_2] [4]
(v) Explain, using collision theory, why the rate decreases at lower temperature. [3]
(c) In the second stage, nitric acid is produced. Balance the equation: .....NO + .....O$_2$ + .....H$_2$O → .....HNO$_3$. [1]

This question is about nitrogen and some of its compounds.
(a) Nitrogen is converted into ammonia, NH$_3$, in the Haber process.
(i) Nitrogen is obtained from air. State the percentage of nitrogen in clean, dry air. [1]
(ii) State the source of hydrogen for the Haber process. [1]
(iii) Complete the dot-and-cross diagram for a molecule of ammonia. Show the outer shell electrons only. ! [2]
(iv) Write a chemical equation for the reaction occurring in the Haber process and give the typical reaction conditions. Include units where appropriate.
Chemical equation: [5]
(b) Ammonia is converted into nitric acid. The first stage uses a catalyst and occurs at 900°C and 5 atm. $$4NH_3(g) + 5O_2(g) \rightarrow 4NO(g) + 6H_2O(g)$$ The forward reaction is exothermic.
(i) Suggest which element is most likely used as a catalyst: calcium, lead, platinum, sodium, sulfur. [1]
(ii) State the oxidation number of nitrogen in:
NH$_3$. [1]
NO. [1]
(iii) Use your answer to explain whether the nitrogen in ammonia undergoes oxidation or reduction. [1]
(iv) Complete Table 3.1 using increases, decreases or no change. ![Table_2] [4]
(v) Explain, using collision theory, why the rate decreases at lower temperature. [3]
(c) In the second stage, nitric acid is produced. Balance the equation: .....NO + .....O$_2$ + .....H$_2$O → .....HNO$_3$. [1]

This question is about sulfuric acid and salts that are made from sulfuric acid.
(a) Zinc reacts with dilute sulfuric acid. Aqueous zinc sulfate is formed.
Zn(s) + H$_2$SO$_4$(aq) → ZnSO$_4$(aq) + H$_2$(g)
(i) Name the limiting reactant. [1]
(ii) State two observations that indicate zinc is in excess. [2]
(iii) Name the filtrate. [1]
(iv) Name two compounds which both react with dilute sulfuric acid to produce aqueous zinc sulfate. [2]
(b) Zinc sulfate crystals are produced by heating ZnSO$_4$ until a saturated solution is formed. When the solution cools, crystals form.
(i) Define a saturated solution. [2]
(ii) Explain why crystals form upon cooling. [1]
(c) Nickel(II) sulfate crystals contain water of crystallisation. When heated, they release water.
NiSO$_4$·xH$_2$O(s) → NiSO$_4$(s) + xH$_2$O(g)
(i) Define crystals containing water of crystallisation. [1]
(ii) State why the solid is heated until no change in mass. [1]
(iii) In an experiment with 0.454 g of NiSO$_4$·xH$_2$O used, anhydrous NiSO$_4$ remaining is 0.310 g. (M$_r$: NiSO$_4$, 155; H$_2$O, 18)
- Determine the value of x in NiSO$_4$·xH$_2$O. [4]

This question is about sulfuric acid and salts that are made from sulfuric acid.
(a) Zinc reacts with dilute sulfuric acid. Aqueous zinc sulfate is formed.
Zn(s) + H$_2$SO$_4$(aq) → ZnSO$_4$(aq) + H$_2$(g)
(i) Name the limiting reactant. [1]
(ii) State two observations that indicate zinc is in excess. [2]
(iii) Name the filtrate. [1]
(iv) Name two compounds which both react with dilute sulfuric acid to produce aqueous zinc sulfate. [2]
(b) Zinc sulfate crystals are produced by heating ZnSO$_4$ until a saturated solution is formed. When the solution cools, crystals form.
(i) Define a saturated solution. [2]
(ii) Explain why crystals form upon cooling. [1]
(c) Nickel(II) sulfate crystals contain water of crystallisation. When heated, they release water.
NiSO$_4$·xH$_2$O(s) → NiSO$_4$(s) + xH$_2$O(g)
(i) Define crystals containing water of crystallisation. [1]
(ii) State why the solid is heated until no change in mass. [1]
(iii) In an experiment with 0.454 g of NiSO$_4$·xH$_2$O used, anhydrous NiSO$_4$ remaining is 0.310 g. (M$_r$: NiSO$_4$, 155; H$_2$O, 18)
- Determine the value of x in NiSO$_4$·xH$_2$O. [4]

This question is about iron.
(a) (i) Describe the bonding in a metallic element such as iron. Labelled diagram may be included. [3]
(ii) Explain why iron conducts electricity when solid. [1]
(b) Iron is extracted from hematite in the blast furnace. !
(i) Give two reasons why coke is added to the blast furnace. [2]
(ii) Explain how limestone removes impurities in hematite. [2]
(iii) Write a symbol equation for the conversion of iron(III) oxide to iron in the blast furnace. [2]
(iv) Suggest why the iron produced in the blast furnace is molten. [1]
(c) Most iron is converted into steel. Explain why the structure of alloys is harder and stronger than pure metals. Diagram can be included. [2]
(d) Iron forms rust. Coating iron with zinc prevents rusting.
(i) Name the substances that react with iron to form rust. [1]
(ii) Name the process using zinc to coat iron. [1]
(iii) Explain how zinc coating prevents rusting if uns. [1]
(iv) Explain how zinc continues to prevent rusting when scratched. [2]

This question is about iron.
(a) (i) Describe the bonding in a metallic element such as iron. Labelled diagram may be included. [3]
(ii) Explain why iron conducts electricity when solid. [1]
(b) Iron is extracted from hematite in the blast furnace. !
(i) Give two reasons why coke is added to the blast furnace. [2]
(ii) Explain how limestone removes impurities in hematite. [2]
(iii) Write a symbol equation for the conversion of iron(III) oxide to iron in the blast furnace. [2]
(iv) Suggest why the iron produced in the blast furnace is molten. [1]
(c) Most iron is converted into steel. Explain why the structure of alloys is harder and stronger than pure metals. Diagram can be included. [2]
(d) Iron forms rust. Coating iron with zinc prevents rusting.
(i) Name the substances that react with iron to form rust. [1]
(ii) Name the process using zinc to coat iron. [1]
(iii) Explain how zinc coating prevents rusting if uns. [1]
(iv) Explain how zinc continues to prevent rusting when scratched. [2]

(a) Esters are members of a homologous series of organic compounds. Give two characteristics of a homologous series. [2]
(b) Ester X has the structure shown: ! Name ester X. [1]
(c) (i) Ester Y has the formula HCOOCH$_2$CH$_2$CH$_3$. Name the alcohol and carboxylic acid used to make it. [2]
(ii) State the molecular formula of ester Y. [1]
(d) Ester Z has the molecular formula C$_4$H$_8$O$_2$. State the empirical formula of ester Z. [1]
(e) Polymers containing ester linkages are known as polyesters. Nylon is a polyamide.
(i) State the term for the polymerisation type for polyesters and polyamides. [1]
(ii) Complete the structures of monomers for nylon. Show all atoms and bonds. ! [2]
(f) Naturally occurring polyamides are found in food.
(i) Name for naturally occurring polyamides. [1]
(ii) Monomer type forming naturally occurring polyamides. [1]

(a) Esters are members of a homologous series of organic compounds. Give two characteristics of a homologous series. [2]
(b) Ester X has the structure shown: ! Name ester X. [1]
(c) (i) Ester Y has the formula HCOOCH$_2$CH$_2$CH$_3$. Name the alcohol and carboxylic acid used to make it. [2]
(ii) State the molecular formula of ester Y. [1]
(d) Ester Z has the molecular formula C$_4$H$_8$O$_2$. State the empirical formula of ester Z. [1]
(e) Polymers containing ester linkages are known as polyesters. Nylon is a polyamide.
(i) State the term for the polymerisation type for polyesters and polyamides. [1]
(ii) Complete the structures of monomers for nylon. Show all atoms and bonds. ! [2]
(f) Naturally occurring polyamides are found in food.
(i) Name for naturally occurring polyamides. [1]
(ii) Monomer type forming naturally occurring polyamides. [1]