Formulas — Paper 2 · IGCSE Science - Combined 0653

16 Which row shows the formulae of sodium hydroxide and of potassium hydroxide? sodium potassium hydroxide hydroxide A NaOH KOH B NaOH POH C SOH KOH D SOH POH

1 marks

Answer: A

This question in 0653/22 Feb/March 2017

17 Aluminium ions have the formula Al 3+. Oxide ions have the formula O2–. What is the formula of aluminium oxide? A Al O B Al O2 C Al 2O3 D Al 3O2

1 marks

Answer: C

This question in 0653/21 May/June 2017

17 Aluminium ions have the formula Al 3+. Oxide ions have the formula O2–. What is the formula of aluminium oxide? A Al O B Al O2 C Al 2O3 D Al 3O2

1 marks

Answer: C

This question in 0653/22 May/June 2017

17 Aluminium ions have the formula Al 3+. Oxide ions have the formula O2–. What is the formula of aluminium oxide? A Al O B Al O2 C Al 2O3 D Al 3O2

1 marks

Answer: C

This question in 0653/23 May/June 2017

18 Aluminium sulfate contains aluminium ions, Al 3+, and sulfate ions, SO4 2–. Iron(II) nitride contains iron(II) ions, Fe2+, and nitride ions, N3–. What are the formulae of aluminium sulfate and of iron(II) nitride? aluminium sulfate iron(II) nitride A Al 2(SO4)3 Fe2N3 B Al 2(SO4)3 Fe3N2 C Al 3(SO4)2 Fe2N3 D Al 3(SO4)2 Fe3N2

1 marks

Answer: B

This question in 0653/21 Oct/Nov 2017

18 The symbols for some ions are shown. name of ion symbol silver Ag+ nitrate NO3 – magnesium Mg2+ chloride Cl – Which symbol equation is correct? A AgNO3 + MgCl → AgCl + MgNO3 B Ag2NO3 + MgCl → Ag2Cl + MgNO3 C 2AgNO3 + MgCl2 → 2AgCl + Mg(NO3)2 D 2AgNO3 + Mg2Cl → 2AgCl + 2MgNO3

1 marks

Answer: C

This question in 0653/22 Oct/Nov 2017

18 The formulae of some ions are shown. ● ammonium, NH4 + ● calcium, Ca2+ ● nitrate, NO3 – ● phosphate, PO4 3– What is the formula of calcium nitrate and of ammonium phosphate? calcium nitrate ammonium phosphate A Ca(NO3)2 NH4(PO4)3 B Ca(NO3)2 (NH4)3PO4 C Ca2NO3 NH4(PO4)3 D Ca2NO3 (NH4)3PO4

1 marks

Answer: B

This question in 0653/23 Oct/Nov 2017

17 The formula of a sodium ion is Na+. The formula of an oxide ion is O2–. What is the formula of sodium oxide? A NaO B NaO2 C Na2O D Na2O3

1 marks

Answer: C

This question in 0653/21 May/June 2018

17 An ion of element X has 8 protons, 8 neutrons and 10 electrons. An ion of element Y has 11 protons, 12 neutrons and 10 electrons. What is the formula of the ionic compound formed between X and Y? A XY B XY2 C X2Y D X2Y2

1 marks

Answer: B

This question in 0653/22 May/June 2018

17 Chromium oxide contains chromium ions, Cr3+, and oxide ions, O2–. What is the formula of chromium oxide? A CrO B CrO2 C Cr2O3 D Cr3O2

1 marks

Answer: C

This question in 0653/23 May/June 2018

17 What is the formula of nitric acid? A HCl B HNO3 C NaOH D NH3

1 marks

Answer: B

This question in 0653/23 Oct/Nov 2018

17 The fertiliser ammonium sulfate has the formula (NH4)2SO4. How many atoms of each element are present in the formula? number of number of number of number of hydrogen atoms nitrogen atoms oxygen atoms sulfur atoms A 4 1 1 1 B 4 2 4 1 C 8 1 4 1 D 8 2 4 1

1 marks

Answer: D

This question in 0653/21 Oct/Nov 2019

16 The fertiliser ammonium sulfate has the formula (NH4)2SO4. How many atoms of each element are present in the formula? number of number of number of number of hydrogen atoms nitrogen atoms oxygen atoms sulfur atoms A 4 1 1 1 B 4 2 4 1 C 8 1 4 1 D 8 2 4 1

1 marks

Answer: D

This question in 0653/22 Oct/Nov 2019

16 The fertiliser ammonium sulfate has the formula (NH4)2SO4. How many atoms of each element are present in the formula? number of number of number of number of hydrogen atoms nitrogen atoms oxygen atoms sulfur atoms A 4 1 1 1 B 4 2 4 1 C 8 1 4 1 D 8 2 4 1

1 marks

Answer: D

This question in 0653/23 Oct/Nov 2019

17 Sodium burns in oxygen forming sodium oxide. An equation for this reaction is shown. xNa + yO2 → zNa2O What are x, y and z? x y z A 2 1 1 B 2 2 1 C 4 1 2 D 4 2 2

1 marks

Answer: C

This question in 0653/21 May/June 2020

17 Aluminium displaces copper from an aqueous solution of its ions. xAl + yCu2+ → xAl 3+ + yCu Which values of x and y balance the equation? x y A 1 2 B 2 1 C 2 3 D 3 2

1 marks

Answer: C

This question in 0653/22 May/June 2020

17 Aqueous lead(II) nitrate, Pb(NO3)2, reacts with potassium iodide to make a precipitate of lead(II) iodide. What is the ionic equation for this reaction? A Pb+ + I–  PbI B Pb2+ + 2I–  PbI2 C Pb(NO3)2 + I–  PbI + 2NO3 – D Pb2+ + 2NO3 – + 2I–  PbI2 + 2NO3 –

1 marks

Answer: B

This question in 0653/21 Oct/Nov 2020

17 The formula of a magnesium ion is Mg2+. The formula of a nitride ion is N3–. What is the formula of magnesium nitride? A MgN B Mg2N2 C Mg2N3 D Mg3N2

1 marks

Answer: D

This question in 0653/22 Oct/Nov 2020

17 Which equation is not correctly balanced? A Ca + 2H2O  Ca(OH)2 + H2 B CaCO3 + 2HCl  CaCl 2 + H2O + CO2 C CaO + 2HCl  CaCl 2 + H2O D Ca(OH)2 + 2HCl  CaCl 2 + H2O

1 marks

Answer: D

This question in 0653/23 Oct/Nov 2020

17 Ammonium phosphate has the formula (NH4)3PO4. Which row shows the formulae of ammonium ions and phosphate ions? ammonium phosphate A NH4 + PO4 – B NH4 3+ PO4 3– C NH4 + PO4 3– D NH4 3+ PO4 –

1 marks

Answer: C

This question in 0653/22 Feb/March 2021

4 What is the balanced equation for photosynthesis? A CO2 + H2O  C6H12O6 + O2 B CO2 + 6H2O  6C6H12O6 + O2 C 6CO2 + 6H2O  C6H12O6 + 6O2 D 6CO2 + 12H2O  6C6H12O6 + 6O2

1 marks

Answer: C

This question in 0653/21 May/June 2021

17 The symbols and charges of some ions are shown. ● aluminium, Al 3+ ● phosphate, PO4 3– ● sodium, Na+ ● sulfate, SO4 2– What are the formulae of aluminium sulfate and sodium phosphate? aluminium sodium sulfate phosphate A Al 2(SO4)3 Na3PO4 B Al 2(SO4)3 Na(PO4)3 C Al 3(SO4)2 Na3PO4 D Al 3(SO4)2 Na(PO4)3

1 marks

Answer: A

This question in 0653/21 May/June 2021

16 Aluminium sulfate is made when aluminium hydroxide, Al (OH)3, reacts with dilute sulfuric acid, H2SO4. What is the formula of aluminium sulfate? A Al SO4 B Al 2SO4 C Al 2(SO4)3 D Al 3(SO4)2

1 marks

Answer: C

This question in 0653/21 Oct/Nov 2021

15 Copper forms two different ions, Cu2+ and Cu+. Copper forms two different oxides. What are the formulae of these two oxides? A CuO2 and Cu2O B Cu2O2 and CuO C Cu2O2 and CuO2 D CuO and Cu2O

1 marks

Answer: D

This question in 0653/22 Oct/Nov 2021

15 The formula of magnesium chloride is MgCl 2. The formula of sodium phosphide is Na3P. What is the formula of magnesium phosphide? A MgP B MgP2 C Mg2P3 D Mg3P2

1 marks

Answer: D

This question in 0653/23 Oct/Nov 2021

16 The formula of sodium phosphate is Na3PO4. The formula of aluminium chloride is Al Cl 3. What is the formula of aluminium phosphate? A Al PO4 B Al (PO4)3 C Al 2(PO4)3 D Al 3PO4

1 marks

Answer: A

This question in 0653/21 May/June 2022

16 Aqueous sodium hydroxide is added to aqueous aluminium sulfate. A white precipitate of aluminium hydroxide is formed. The ionic equation for this reaction is shown. Al 3+(aq) + 3OH–(aq)  Al (OH)3(s) What is the full symbol equation for this reaction? A Al SO4(aq) + 3NaOH(aq)  Al (OH)3(s) + Na3SO4(aq) B Al 2(SO4)3(aq) + NaOH(aq)  Al (OH)3(s) + Na2SO4(aq) C Al 2(SO4)3(aq) + 6NaOH(aq)  2Al (OH)3(s) + 3Na2SO4(aq) D Al 3(SO4)2(aq) + 9NaOH(aq)  3Al (OH)3(s) + 2Na2SO4(aq)

1 marks

Answer: C

This question in 0653/21 Oct/Nov 2022

16 Potassium phosphate is an ionic compound used in fertilisers. Phosphate ions have the symbol PO4 3–. What is the formula for potassium phosphate? A KPO4 B K(PO4)3 C K2PO4 D K3PO4

1 marks

Answer: D

This question in 0653/22 Oct/Nov 2022

17 Sodium burns in oxygen forming sodium oxide. An equation for this reaction is shown. xNa + yO2 → zNa2O What are x, y and z? x y z A 2 1 2 B 2 2 1 C 4 1 2 D 4 2 2

1 marks

Answer: C

This question in 0653/21 May/June 2023

17 Aqueous lead(II) nitrate, Pb(NO3)2, reacts with aqueous potassium iodide to make a precipitate of lead(II) iodide. What is the ionic equation for this reaction? A Pb+ + I–  PbI B Pb2+ + 2I–  PbI2 C Pb(NO3)2 + I–  PbI + 2NO3 – D Pb2+ + 2NO3 – + 2I–  PbI2 + 2NO3 –

1 marks

Answer: B

This question in 0653/22 May/June 2023

17 Aqueous sodium sulfate reacts with aqueous barium chloride to make barium sulfate and sodium chloride. What is the ionic equation for this reaction? A Ba2+(aq) + SO4 2–(aq)  BaSO4(aq) B Ba2+(aq) + SO4 2–(aq)  BaSO4(s) C Na+(aq) + Cl –(aq)  NaCl (s) D Na+(aq) + Cl –(aq)  NaCl (aq)

1 marks

Answer: B

This question in 0653/23 May/June 2023

17 Iron(III) sulfate contains Fe3+ ions and SO4 2– ions. What is the formula of iron(III) sulfate? A FeSO4 B Fe3SO4 C Fe2(SO4)3 D Fe3(SO4)2

1 marks

Answer: C

This question in 0653/21 Oct/Nov 2023

17 An ionic compound contains ammonium ions, NH4 +, iron(III) ions, Fe3+, and sulfate ions, SO4 2–. What is the formula of this compound? A NH4FeSO4 B NH4Fe(SO4)2 C (NH4)2FeSO4 D NH4Fe3(SO4)2

1 marks

Answer: B

This question in 0653/22 Oct/Nov 2023

17 An ionic compound contains the ions NH4 + and S2O3 2–. What is the formula of this compound? A NH4S2O3 B NH4(S2O3)2 C (NH4)2S2O3 D 2NH4S2O3

1 marks

Answer: C

This question in 0653/22 Feb/March 2024

17 The formula of magnesium nitrate is Mg(NO3)2. Which symbols represent the ions in magnesium nitrate? magnesium nitrate A Mg+ NO3 – B Mg+ NO3 2– C Mg2+ NO3 2– D Mg2+ NO3 –

1 marks

Answer: D

This question in 0653/21 May/June 2024

17 A solution of barium chloride reacts with dilute sulfuric acid to form a precipitate. What is the ionic equation for this reaction? A Ba2+(aq) + SO4 2–(aq)  BaSO4(aq) B Ba2+(aq) + SO4 2–(aq)  BaSO4(s) C BaCl 2(s) + H2SO4(aq)  BaSO4(aq) + 2HCl (aq) D Ba2+(aq) + 2Cl –(aq) + 2H+(aq) + SO4 2–(aq)  BaSO4(s) + 2HCl (aq)

1 marks

Answer: B

This question in 0653/22 May/June 2024

18 Magnesium reacts with dilute hydrochloric acid forming magnesium chloride and hydrogen. Which equation is correct for this reaction? A Mg + 2HCl  MgCl + H2 B Mg + 2HCl  MgCl 2 + H2 C Mg + HCl  MgCl + H D 2Mg + 2HCl  MgCl 2 + H2

1 marks

Answer: B

This question in 0653/23 May/June 2024

17 The equation for the reaction between barium nitrate and sodium sulfate is shown. Ba(NO3)2(aq) + Na2SO4(aq)  BaSO4(s) + 2NaNO3(aq) What is the ionic equation for this reaction? A Ba+(aq) + SO4 –(aq)  BaSO4(s) B Na+(aq) + NO3 –(aq)  NaNO3(aq) C Ba2+(aq) + SO4 2–(aq)  BaSO4(s) D Ba2+(aq) + SO4 2–(aq)  Ba2+(s) + SO4 2–(s)

1 marks

Answer: C

This question in 0653/21 Oct/Nov 2024

17 What are the correct numbers of atoms in one molecule of nitric acid? hydrogen nitrogen oxygen A 1 1 3 B 1 3 1 C 2 1 3 D 2 3 1

1 marks

Answer: A

This question in 0653/23 Oct/Nov 2024

18 Calcium carbonate reacts with dilute hydrochloric acid to make calcium chloride, carbon dioxide and water. What is the balanced symbol equation and correct state symbols for this reaction? A CaCO3(s) + HCl (aq)  CaCl 2(aq) + CO2(g) + H2O(l) B CaCO3(s) + HCl (l)  CaCl 2(s) + CO2(g) + H2O(aq) C CaCO3(s) + 2HCl (aq)  CaCl 2(aq) + CO2(g) + H2O(l) D CaCO3(s) + 2HCl (l)  CaCl 2(s) + CO2(g) + H2O(aq)

1 marks

Answer: C

This question in 0653/22 Feb/March 2025

4 What is the balanced equation for photosynthesis? A CO2 + H2O  C6H12O6 + O2 B CO2 + 6H2O  6C6H12O6 + O2 C 6CO2 + 6H2O  C6H12O6 + 6O2 D 6CO2 + 12H2O  6C6H12O6 + 6O2

1 marks

Answer: C

This question in 0653/21 May/June 2025

18 The formula of sodium phosphate is Na3PO4. The formula of calcium nitrate is Ca(NO3)2. Which row shows the formula for calcium phosphate and the formula for sodium nitrate? calcium phosphate sodium nitrate A Ca2(PO4)3 NaNO3 B Ca2(PO4)3 Na(NO3)2 C Ca3(PO4)2 NaNO3 D Ca3(PO4)2 Na(NO3)2

1 marks

Answer: C

This question in 0653/21 May/June 2025

17 The formula of an iron(III) ion is Fe3+. The formula of a sulfate ion is SO4 2–. What is the formula of iron(III) sulfate? A FeSO4 B Fe3SO4 C Fe2(SO4)3 D Fe3(SO4)2

1 marks

Answer: C

This question in 0653/22 Oct/Nov 2025