IGCSE Chemistry 0620 Paper 23, Oct/Nov 2024

A sample of ethanol is left in an open beaker at room temperature. After 24 hours, no ethanol remains in the beaker. What has happened to the ethanol? A It has boiled. B It has condensed. C It has evaporated. D It has frozen.

A gas is in a sealed container with a fixed volume. Which statements describe what happens to the molecules in the gas when the temperature is increased? 1 They move more slowly. 2 They collide with the walls of the container more frequently. 3 They collide with the walls of the container with less force. 4 They have greater kinetic energy. A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4

What happens when sodium atoms combine with chlorine atoms to form sodium chloride? A Sodium atoms each gain one electron, and chlorine atoms each lose one electron. B Sodium atoms each lose one electron, and chlorine atoms each gain one electron. C Sodium atoms and chlorine atoms share one electron with each other. D Sodium atoms and chlorine atoms share two electrons with each other.

The table shows some properties of four substances.

Which substances are ionic? A 1, 3 and 4 B 1 and 3 only C 2 and 4 D 2 only

Which statement about methane is correct? A In methane, positive hydrogen ions are attracted to negative carbon ions. B In methane, electrons are shared between carbon atoms and hydrogen atoms. C Methane has a high boiling point. D Methane is a good conductor of electricity.

A sample of iridium has a relative atomic mass of 192.29. The sample contains two isotopes only. 64.50% of the sample is ${}^{193}\text{Ir}$. What is the other isotope in the sample? A ${}^{189}\text{Ir}$ B ${}^{190}\text{Ir}$ C ${}^{191}\text{Ir}$ D ${}^{192}\text{Ir}$

Ammonium iron(III) citrate contains in its formula: • more than one ammonium ion • one iron ion • two ${\text{C}}_6{\text{H}}_4{\text{O}}_7^{4-}$ ions. What is the formula of ammonium iron(III) citrate? A $({\text{NH}}_4{)}_4\text{Fe}({\text{C}}_6{\text{H}}_4{\text{O}}_7{)}_2$ B $({\text{NH}}_4{)}_5\text{Fe}({\text{C}}_6{\text{H}}_4{\text{O}}_7{)}_2$ C $({\text{NH}}_4{)}_6\text{Fe}({\text{C}}_6{\text{H}}_4{\text{O}}_7{)}_2$ D $({\text{NH}}_4{)}_7\text{Fe}({\text{C}}_6{\text{H}}_4{\text{O}}_7{)}_2$

Silicon(IV) oxide reacts with chlorine and carbon to form liquid silicon(IV) chloride, ${\text{SiCl}}_4$, and carbon dioxide gas. If the reaction is carried out at r.t.p., which symbol equation represents this reaction? A ${\text{SiO}}_2\text{(l)}+2{\text{Cl}}_2\text{(g)}+\text{C(s)}\to {\text{SiCl}}_4\text{(l)}+{\text{CO}}_2\text{(g)}$ B ${\text{SiO}}_2\text{(l)}+2{\text{Cl}}_2\text{(g)}+\text{C(g)}\to {\text{SiCl}}_4\text{(l)}+{\text{CO}}_2\text{(g)}$ C ${\text{SiO}}_2\text{(s)}+2{\text{Cl}}_2\text{(g)}+\text{C(s)}\to {\text{SiCl}}_4\text{(g)}+{\text{CO}}_2\text{(g)}$ D ${\text{SiO}}_2\text{(s)}+2{\text{Cl}}_2\text{(g)}+\text{C(s)}\to {\text{SiCl}}_4\text{(l)}+{\text{CO}}_2\text{(g)}$

The structure of ethene is shown. How many hydrogen atoms and how many carbon atoms are in one mole of ethene?

A known volume and concentration of aqueous sodium hydroxide is titrated against dilute hydrochloric acid. The volume of dilute hydrochloric acid needed to exactly neutralise the sodium hydroxide is measured. Five calculation steps are shown. 1 Calculate the amount of hydrochloric acid in moles. 2 Calculate the relative formula mass of hydrochloric acid. 3 Calculate the concentration of hydrochloric acid in $\text{g}\mathrm{/}{\text{dm}}^3$. 4 Calculate the amount of sodium hydroxide in moles. 5 Calculate the concentration of hydrochloric acid in $\text{mol}\mathrm{/}{\text{dm}}^3$. What is the order of these steps to calculate the concentration of the hydrochloric acid in $\text{g}\mathrm{/}{\text{dm}}^3$? A $1\to 4\to 3\to 5\to 2$ B $1\to 2\to 4\to 5\to 3$ C $4\to 1\to 5\to 2\to 3$ D $4\to 2\to 1\to 3\to 5$

Two different substances are electrolysed using inert electrodes in two separate experiments. Hydrogen is produced in both experiments. Which row identifies the two substances and the electrode at which hydrogen is produced?

Aqueous copper(II) sulfate can be electrolysed using either carbon electrodes or copper electrodes. Which statement describes what happens at the positive electrode? A Copper is deposited if the electrode is made from carbon. B Copper is deposited if the electrode is made from copper. C Oxygen gas is produced if the electrode is made from carbon. D Oxygen gas is produced if the electrode is made from copper.

Which statement about a hydrogen–oxygen fuel cell is not correct? A Chemical energy is converted into electrical energy. B Hydrogen is oxidised. C The reaction that takes place is endothermic. D Water is the only chemical product.

Which reaction pathway diagram is correctly labelled? A Reaction pathway diagram with reactants, products, $E_a$, $\mathrm{\Delta }H$ B Reaction pathway diagram with reactants, products, $E_a$, $\mathrm{\Delta }H$ C Reaction pathway diagram with reactants, products, $E_a$, $\mathrm{\Delta }H$ D Reaction pathway diagram with reactants, products, $E_a$, $\mathrm{\Delta }H$

Which row describes a reaction where the overall energy change is exothermic?

Which process involves a physical change only? A heating calcium carbonate strongly B burning wood C melting an ice cube D mixing an acid and a base

In the Haber process, an equilibrium is established. $${\text{N}}_2\text{(g)}+3{\text{H}}_2\text{(g)}\rightleftharpoons 2{\text{NH}}_3\text{(g)}$$ The forward reaction is exothermic. Which change to the reaction conditions will move the position of equilibrium to the left? A decreasing the pressure by 100 atm B decreasing the temperature by 100 °C C adding more nitrogen gas to the mixture D removing the iron catalyst

The flow chart shows some properties of a metal oxide. What is the metal oxide? A aluminium oxide B copper(II) oxide C iron(III) oxide D zinc oxide

Which statement about reactants in redox reactions is correct? A An oxidising agent donates electrons, and a reducing agent accepts electrons. B When one element gains electrons, the oxidation number of a different element increases. C When the oxidation number of one element increases, a different element gains oxygen. D When the oxidation number of one element increases, a different element loses electrons.

Aluminium is extracted from aluminium oxide by electrolysis. The ionic half-equation for the reaction at one of the electrodes is shown. $${\text{Al}}^{3+}+3{\text{e}}^{-}\to \text{Al}$$ Which row describes the change in oxidation number of the aluminium and the type of reaction at this electrode?

Which statement about dilute hydrochloric acid is correct? A It is a strong acid as it fully dissociates. B It is a strong acid as it partially dissociates. C It is a weak acid as it fully dissociates. D It is a weak acid as it partially dissociates.

Which row describes and gives the formula of hydrated copper(II) sulfate?

The equations for three reactions are shown. 1 ${\text{Pb(NO}}_3{)}_2\text{(aq)}+2\text{KI(aq)}\to {\text{PbI}}_2\text{(s)}+2{\text{KNO}}_3\text{(aq)}$ 2 $2{\text{AgNO}}_3\text{(aq)}+{\text{CuI}}_2\text{(aq)}\to {\text{Cu(NO}}_3{)}_2\text{(aq)}+2\text{AgI(s)}$ 3 $\text{CuO(s)}+{\text{H}}_2{\text{SO}}_4\text{(aq)}\to {\text{CuSO}}_4\text{(aq)}+{\text{H}}_2\text{O(l)}$ Which reactions are suitable for making a salt by precipitation? A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3

Acidified potassium dichromate(VI), ${\text{K}}_2{\text{Cr}}_2{\text{O}}_7$, is used to oxidise ethanol, ${\text{C}}_2{\text{H}}_5\text{OH}$. The ionic equation for the reaction is shown. $$3{\text{C}}_2{\text{H}}_5\text{OH}+2{\text{Cr}}_2{\text{O}}_7^{2-}+16{\text{H}}^{+}\to 3{\text{CH}}_3\text{COOH}+4{\text{Cr}}^{3+}+11{\text{H}}_2\text{O}$$ Which properties of transition elements are shown by chromium in this reaction?

Which statements describe the Periodic Table? 1 The elements are arranged in order of their nucleon number. 2 The elements are arranged in order of their proton number. 3 It is used to predict the properties of elements. A 1 and 3 B 1 only C 2 and 3 D 2 only

Which row shows the correct order of reactivity of the four named metals?

Four iron nails are added to four different metal sulfate solutions. In which solution does a displacement reaction occur? A copper(II) sulfate B magnesium sulfate C sodium sulfate D zinc sulfate

A fertiliser contains ammonium nitrate and potassium phosphate. Why is the fertiliser described as an NPK fertiliser? A It provides nitrogen, which is an essential element for improved plant growth. B It contains the element oxygen, which neutralises acidic soil. C It contains the elements nitrogen and phosphorus. D It provides the three main elements needed for improved plant growth.

What are the approximate percentages of oxygen and nitrogen in clean, dry air?

Which compounds have similar chemical properties? A butanol and butanoic acid B ethane and ethene C methane and butane D propene and propanol

Four statements about organic compounds P, Q, R and S are listed. P is a saturated hydrocarbon. The formula of Q is ${\text{CH}}_3{\text{CH}}_3$. A molecule of R contains only one oxygen atom. Compound S is a carboxylic acid. Which statement about these compounds is correct? A P and Q are members of different homologous series. B P and S are members of the same homologous series. C Q and S are members of the same homologous series. D Q, R and S are all members of different homologous series.

The structure of an organic compound is shown. What is the name of the compound? A chloroethane B chloroethene C chloroethanol D chloroethanoic acid

Which statement about the manufacture of ethene from larger alkane molecules is correct? A A low temperature is required. B The process is called cracking. C The process requires an excess of oxygen. D Water is also a product.

Which processes are used to make ethanoic acid? 1 heating ethanol with acidified aqueous potassium manganate(VII) 2 bacterial oxidation of ethanol 3 distilling ethanol using a fractionating column A 1 and 2 B 1 only C 2 and 3 D 3 only

Which statement about propene, ${\text{C}}_3{\text{H}}_6$, is correct? A Propene reacts with bromine in the dark in a substitution reaction. B Propene reacts with steam in the presence of an alkaline catalyst, forming an alcohol. C Propene undergoes addition polymerisation, forming poly(ethene). D Propene undergoes an addition reaction to form an alkane.

How many of each type of bond are present in ethanoic acid, ${\text{CH}}_3\text{COOH}$?

Which diagram represents the structure of a protein?

The chromatogram of substance S is shown. Some distances, W, X, Y and Z, are labelled on the diagram. How is the $R_f$ value of substance S calculated? A ${\displaystyle \frac{X}{Y}}$ B ${\displaystyle \frac{W}{Z}}$ C ${\displaystyle \frac{Y}{X}}$ D ${\displaystyle \frac{Y}{W}}$

Some information about solid silver chloride and solid sodium chloride is shown. • Silver chloride and sodium chloride do not dissolve in kerosene. • Silver chloride is insoluble in water, but sodium chloride is soluble in water. • The boiling point of silver chloride is 1547 °C and the boiling point of sodium chloride is 1413 °C. Which processes are used to separate a mixture of solid silver chloride and solid sodium chloride? A add kerosene, stir and then filter B add water, stir and then filter C add water, stir and then leave to crystallise D add water, stir and then perform fractional distillation

Which statement describes how a flame test is done? A The tip of a clean wire is dipped into the substance and the wire is placed in a blue Bunsen burner flame. B The tip of a clean wire is dipped into the substance and the wire is placed in a yellow Bunsen burner flame. C A wooden splint is lit and is placed above a test-tube containing the gas being tested. D A wooden splint is lit, blown out and the glowing splint put into a test-tube of the gas being tested.