IGCSE Chemistry 0620 Paper 43, Oct/Nov 2023

gives a lilac colour in a flame test

forms a cream precipitate when its aqueous solution reacts with acidified aqueous silver nitrate

is an acidic oxide

is an unsaturated hydrocarbon

is a product of incomplete combustion of fossil fuels

is used to test for the presence of water.

Give the letters of all the particles which are: atoms

Give the letters of all the particles which are: ions with a charge of 2–

Give the letters of all the particles which are: cations.

State the atomic number of A.

Determine the number of nucleons in D.

State the electronic configuration of D.

State the group number of F.

State the period number of B.

Nitrogen is converted into ammonia, ${\mathrm{N}\mathrm{H}}_3$, in the Haber process. Nitrogen is obtained from air. State the percentage of nitrogen in clean, dry air.

State the source of hydrogen for the Haber process.

Complete the dot-and-cross diagram in Fig. 3.1 for a molecule of ammonia. Show the outer shell electrons only.

Write a chemical equation for the reaction occurring in the Haber process and give the typical reaction conditions. Include units where appropriate. chemical equation ............................................................................................................... reaction conditions: temperature ........................................................................................................................ pressure .............................................................................................................................. catalyst ...............................................................................................................................

Ammonia is converted into nitric acid. The first stage of this conversion uses a catalyst and occurs at a temperature of $900{}^{\circ }\mathrm{C}$ and a pressure of 5 atmospheres. $$4{\mathrm{N}\mathrm{H}}_3(\mathrm{g})+5{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 4\mathrm{N}\mathrm{O}(\mathrm{g})+6{\mathrm{H}}_2\mathrm{O}(\mathrm{g})$$ The forward reaction is exothermic. Suggest which of the following elements is most likely to be used as a catalyst. Draw a circle around your answer. calcium lead platinum sodium sulfur

State the oxidation number of nitrogen in: ${\mathrm{N}\mathrm{H}}_3$ ..................................................................................................................................... NO ......................................................................................................................................

Use your answer to (ii) to explain whether the nitrogen in ammonia undergoes oxidation or reduction.

Complete Table 3.1 using the words increases, decreases or no change. Table 3.1

Decreasing the temperature causes the rate of the forward reaction to decrease. Explain, using collision theory, why the rate of the reaction is slower at the decreased temperature.

In the second stage, nitric acid is produced. Balance the symbol equation for this reaction. .....$\mathrm{N}\mathrm{O}+$ .....${\mathrm{O}}_2+$ .....${\mathrm{H}}_2\mathrm{O}\to$ .....${\mathrm{H}\mathrm{N}\mathrm{O}}_3$

Zinc reacts with dilute sulfuric acid. Aqueous zinc sulfate is one of the products. Powdered zinc is added to dilute sulfuric acid. The mixture is stirred. More zinc is added, with stirring, until the zinc is in excess. $$\mathrm{Z}\mathrm{n}(\mathrm{s})+{\mathrm{H}}_2{\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})\to {\mathrm{Z}\mathrm{n}\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})+{\mathrm{H}}_2(\mathrm{g})$$ The mixture is then filtered. Name the limiting reactant.

State two observations that indicate the zinc is in excess. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Name the filtrate.

Name two compounds which both react with dilute sulfuric acid to produce aqueous zinc sulfate. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Zinc sulfate crystals are produced by heating aqueous zinc sulfate until a saturated solution is formed. When the saturated solution cools down, crystals of zinc sulfate start to form. State what is meant by the term saturated solution.

Explain why crystals form when the saturated solution cools down.

Nickel(II) sulfate crystals contain water of crystallisation. When nickel(II) sulfate crystals, ${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4\cdot x{\mathrm{H}}_2\mathrm{O}$, are heated, they give off water. $${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4\cdot x{\mathrm{H}}_2\mathrm{O}(\mathrm{s})\to {\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4(\mathrm{s})+x{\mathrm{H}}_2\mathrm{O}(\mathrm{g})$$ A student carries out an experiment to determine the value of $x$ in ${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4\cdot x{\mathrm{H}}_2\mathrm{O}$. step 1 Nickel(II) sulfate crystals are weighed. step 2 Nickel(II) sulfate crystals are heated. step 3 The remaining solid is allowed to cool and is then weighed. step 4 The remaining solid is heated again, allowed to cool and is then weighed. step 5 Step 4 is repeated until there is no change in mass. State the term used to describe crystals that contain water of crystallisation.

State why step 4 is repeated until there is no change in mass.

In an experiment, $0.454\mathrm{g}$ of nickel(II) sulfate crystals, ${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4\cdot x{\mathrm{H}}_2\mathrm{O}$, is used. The mass of anhydrous nickel(II) sulfate, ${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4$, remaining is $0.310\mathrm{g}$. [$M_{\mathrm{r}}$: ${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4$, 155; ${\mathrm{H}}_2\mathrm{O}$, 18] Determine the value of $x$ in ${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4\cdot x{\mathrm{H}}_2\mathrm{O}$. Use the following steps. $\bullet$ Calculate the number of moles of ${\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4$ remaining. $$\text{moles of }{\mathrm{N}\mathrm{i}\mathrm{S}\mathrm{O}}_4=\text{..............................}$$ $\bullet$ Calculate the mass of ${\mathrm{H}}_2\mathrm{O}$ given off. $$\text{mass of }{\mathrm{H}}_2\mathrm{O}=\text{.............................. g}$$ $\bullet$ Calculate the number of moles of ${\mathrm{H}}_2\mathrm{O}$ given off. $$\text{moles of }{\mathrm{H}}_2\mathrm{O}=\text{..............................}$$ $\bullet$ Calculate the value of $x$. $$x=\text{..............................}$$

Describe the bonding in a metallic element such as iron. You may include a labelled diagram as part of your answer.

Explain why iron conducts electricity when it is solid.

Iron is extracted from hematite in the blast furnace as shown in Fig. 5.1. Give two reasons why coke is added to the blast furnace. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Explain how limestone removes the impurities in the hematite.

Hematite contains iron(III) oxide. Write a symbol equation for the conversion of iron(III) oxide to iron in the blast furnace.

Suggest why the iron produced in the blast furnace is molten.

Most iron is converted into steel. Steel is an alloy. Steel is more useful than pure iron because it is harder and stronger. Explain why the structure of alloys causes them to be harder and stronger than pure metals. You may include a diagram as part of your answer.

Iron forms rust. Rusting is prevented by coating iron with zinc. Name the substances that react with iron to form rust.

Name the process in which zinc is used to coat iron to prevent rusting.

Explain how the coating of zinc prevents rusting if the zinc is not scratched.

When zinc is scratched the iron becomes exposed. Explain how the zinc continues to prevent rusting.

Esters are members of a homologous series of organic compounds. Give two characteristics that are the same for all members of a homologous series. 1 ................................................................................................................................................. 2 .................................................................................................................................................

Ester X has the structure shown in Fig. 6.1. Name ester X.

Ester Y has the structural formula ${\mathrm{H}\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_3$. Name the alcohol and the carboxylic acid used to make ester Y. alcohol .................................................................................................................... carboxylic acid ....................................................................................................................

State the molecular formula of ester Y.

Ester Z has the molecular formula ${\mathrm{C}}_4{\mathrm{H}}_8{\mathrm{O}}_2$. State the empirical formula of ester Z.

Polymers containing ester linkages are known as polyesters. Polyamides are another type of polymer. Nylon is a polyamide. The structure of nylon is shown in Fig. 6.2. State the term used to describe the type of polymerisation used to produce polyesters and polyamides.

Complete Fig. 6.3 to show the structures of the monomers used to produce nylon. Show all of the atoms and all of the bonds.

Naturally occurring polyamides are found in food. State the name given to naturally occurring polyamides.

Name the type of monomer which forms naturally occurring polyamides.