IGCSE Chemistry 0620 Paper 31, Oct/Nov 2023

turns from blue to colourless when an acid is added

is in many fertilisers

is a salt which has a negative ion with a charge of 2–

is a waste gas from digestion in animals

is a hydrocarbon with a total of five atoms in a molecule

is a compound of a transition element.

Fig. 2.1 shows the distillation apparatus that can be used to separate water from aqueous copper(II) sulfate. Explain how distillation separates water from aqueous copper(II) sulfate.

Fig. 2.2 shows a fractionating column for separating petroleum into different hydrocarbon fractions. On Fig. 2.2, draw an X inside the column to show where the hydrocarbon with the highest viscosity collects.

Name the fraction labelled A in Fig. 2.2.

State the name of the fraction in Fig. 2.2 which has the lowest boiling point.

State one use of the bitumen fraction.

Table 3.1 shows the average concentrations, in $\mathrm{n}\mathrm{g}\mathrm{/}1000{\mathrm{c}\mathrm{m}}^3$, of air pollutants in four different years. Name the pollutant that has the lowest concentration in 2019.

Name the pollutant that shows a continuous decrease in concentration from 2019 to 2022.

Calculate the average mass, in $\mathrm{n}\mathrm{g}$, of sulfur dioxide in a $250{\mathrm{c}\mathrm{m}}^3$ sample of polluted air in 2020. mass = .............................. $\mathrm{n}\mathrm{g}$

State one source of sulfur dioxide in the atmosphere.

State one adverse effect of sulfur dioxide in the atmosphere.

Choose the compound used to remove sulfur dioxide in flue gas desulfurisation. Tick (✓) one box. aluminium chloride calcium oxide methane sulfuric acid

Hydrochloric acid reacts with sodium sulfite. The products are sodium chloride, sulfur dioxide and a liquid which turns anhydrous cobalt(II) chloride pink. Complete the symbol equation for this reaction. $\mathrm{N}{\mathrm{a}}_2\mathrm{S}{\mathrm{O}}_3+\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{H}\mathrm{C}\mathrm{l}\to 2\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}+\mathrm{S}{\mathrm{O}}_2+\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}$

Name the acidified solution used to test for sulfur dioxide gas and state the observations. acidified solution ................................................................................................................. observations .......................................................................................................................

Ammonia forms an alkaline solution in water. Give the formula of the ion that is present in all alkaline solutions.

Choose from the list the pH value for an alkaline solution. Draw a circle around your chosen answer. pH 1 pH 4 pH 7 pH 13

State two general properties of a liquid. 1 ................................................................................................................................................. .................................................................................................................................................... 2 ................................................................................................................................................. ....................................................................................................................................................

Fig. 4.1 shows the physical states of bromine. Name the changes of physical states A and B. A ................................................................................................................................................ B ................................................................................................................................

Describe liquid bromine and bromine gas in terms of the arrangement and motion of the particles. liquid bromine arrangement .............................................................................................................................. .................................................................................................................................................... motion ........................................................................................................................................ .................................................................................................................................................... bromine gas arrangement .............................................................................................................................. .................................................................................................................................................... motion ........................................................................................................................................ ....................................................................................................................................................

A sealed gas syringe contains $80{\mathrm{c}\mathrm{m}}^3$ of bromine gas. State how decreasing the pressure affects the volume of bromine gas in the gas syringe when the temperature remains constant.

Table 5.1 shows some properties of some Group I metals. Use the information in Table 5.1 to predict: the melting point of rubidium

the solubility of sodium hydroxide at room temperature

the observations when potassium reacts with water

the physical state of caesium at 20°C. Give a reason for your answer. physical state ...................................................................................................................... reason ................................................................................................................................. .......................................................................................................................................

Iron is extracted in a blast furnace by reduction of iron(III) oxide, $\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_3$, with carbon monoxide. Carbon monoxide is produced by the reaction of carbon with carbon dioxide. $$\mathrm{C}+\mathrm{C}{\mathrm{O}}_2\to 2\mathrm{C}\mathrm{O}$$ Explain how this equation shows that carbon dioxide is reduced.

Name the type of chemical reaction where oxidation and reduction take place simultaneously.

Calcium carbonate is added to the blast furnace. The calcium carbonate undergoes thermal decomposition. State the meaning of the term thermal decomposition.

Stainless steel is an alloy of iron. Give one reason why alloys are more useful than pure metals.

Brass is an alloy. Choose the diagram, A, B, C or D, in Fig. 5.1 that best shows the structure of brass. diagram .........................................................................................................................

Table 5.2 gives some observations about the reactivity of four metals with dilute hydrochloric acid. Put the four metals in order of their reactivity. Put the least reactive metal first.

Fig. 6.1 shows the volume of carbon dioxide gas released as the reaction proceeds. Deduce the volume of carbon dioxide gas released after 2 minutes. volume of carbon dioxide = .............................. ${\mathrm{c}\mathrm{m}}^3$

The student repeats the experiment using the same volume of hydrochloric acid but with a higher concentration. The magnesium carbonate is still in excess. All other conditions stay the same. Draw a line on the grid in Fig. 6.1 to show the volume of carbon dioxide released when hydrochloric acid with a higher concentration is used.

The student repeats the experiment using smaller pieces of magnesium carbonate. All other conditions stay the same. Describe how the rate of reaction differs when smaller pieces of magnesium carbonate are used.

The student repeats the experiment at 10°C. All other conditions stay the same. Describe how the rate of reaction differs when the temperature is 10°C.

Hydrochloric acid reacts with iron. Complete the word equation for this reaction.

Acids are used as catalysts in many chemical reactions. State the meaning of the term catalyst.

Fig. 7.1 shows the displayed formula of compound S. On Fig. 7.1, draw a circle around the carboxylic acid functional group.

Deduce the molecular formula of compound S.

Compound S can be converted to acrylic acid. The molecular formula of acrylic acid is ${\mathrm{C}}_3{\mathrm{H}}_4{\mathrm{O}}_2$. Complete Table 7.1 to calculate the relative molecular mass of acrylic acid. relative molecular mass = ..............................

Acrylic acid is an unsaturated compound. Describe a test for an unsaturated compound. test ...................................................................................................................................... observations .......................................................................................................................

When left in the air, acrylic acid forms a polymer. State the meaning of the term polymer.

Poly(ethene) is also a polymer. Choose from the list the type of polymerisation that occurs when poly(ethene) is made. Draw a circle around your chosen answer. substitution oxidation neutralisation addition

Ethanoic acid is a carboxylic acid. Complete the word equation for the reaction of ethanoic acid with sodium hydroxide.

Ethanoic acid can be converted to ethanol. Name the two products formed when ethanol undergoes complete combustion. ................................................................... and ...................................................................

State the meaning of the term ionic bond.

Complete Fig. 8.1 to show: • the electronic configuration of a lithium ion • the charge on the ion.

Deduce the number of protons and neutrons in the bromide ion shown. ${}_{35}^{79}\mathrm{B}{\mathrm{r}}^{-}$ number of protons ..................................................................................................................... number of neutrons ...................................................................................................................

Molten lithium bromide is electrolysed using graphite electrodes. State the names of the product at each electrode and give the observations at the positive electrode. product at the negative electrode .............................................................................................. product at the positive electrode ................................................................................................ observations at the positive electrode ....................................................................................................................................................

Fig. 8.2 shows the structure of graphite. State the type of bonding in graphite.

Explain by referring to Fig. 8.2 why graphite is used as a lubricant.

Graphite and diamond are both forms of carbon. State one use of diamond.