Identification of ions and gases — Paper 2 · IGCSE Sciences - Co-ordinated (Double) 0654

23 Four solutions are tested with Universal Indicator paper and with anhydrous copper(II) sulfate. Which row shows the observations for pure water? Universal Indicator paper anhydrous copper(II) sulfate A turns blue turns blue B turns blue turns white C turns green turns blue D turns green turns white

1 marks

Answer: C

This question in 0654/21 May/June 2017

20 Some properties of gas Y are listed. 1 It burns to produce only one product. 2 It has no effect on damp litmus paper. 3 It is a covalent compound containing two different elements. What is gas Y? A carbon dioxide B carbon monoxide C chlorine D methane

1 marks

Answer: B

This question in 0654/22 May/June 2017

16 The electrolysis of concentrated aqueous sodium chloride is an important industrial process. During this process ««1«« is produced at the cathode and ««2«« is produced at the anode. The solution formed turns litmus ««3«« . Which words complete gaps 1, 2 and 3? 1 2 3 A hydrogen chlorine blue B hydrogen oxygen blue C sodium chlorine red D sodium oxygen red

1 marks

Answer: A

This question in 0654/23 May/June 2017

23 Which row shows a chemical test for the presence of water? substance colour change A anhydrous cobalt(II) chloride pink to blue B anhydrous cobalt(II) chloride white to blue C anhydrous copper(II) sulfate pink to blue D anhydrous copper(II) sulfate white to blue

1 marks

Answer: D

This question in 0654/23 May/June 2017

26 When dilute sulfuric acid is added to a metal carbonate, gas M is produced. What is M? A ammonia B carbon dioxide C hydrogen D sulfur dioxide

1 marks

Answer: B

This question in 0654/23 May/June 2019

14 Which observation shows that a substance is pure water? A It boils between 100 °C and 102 °C. B It melts at 0 °C and boils at 100 °C. C It turns copper(II) sulfate from white to blue. D It turns cobalt(II) chloride from pink to blue.

1 marks

Answer: B

This question in 0654/22 Oct/Nov 2019

3 A food contains reducing sugar, but no starch. What colours will be obtained if samples of the food are tested with Benedict’s solution and with iodine solution? Benedict’s test iodine test A blue blue-black B blue brown C red-orange blue-black D red-orange brown

1 marks

Answer: D

This question in 0654/21 May/June 2020

10 An experiment using germinating seeds is set up as shown, and left at room temperature for 12 hours. to pump solution P solution Q germinating damp peas cotton wool The pump is then switched on and air is drawn through the apparatus for 2 minutes. Which row identifies solutions P and Q and the results obtained? solution P solution P results solution Q solution Q results A ethanol remains colourless ethanol turns milky B ethanol turns milky limewater remains colourless C limewater remains colourless limewater turns milky D limewater turns milky ethanol remains colourless

1 marks

Answer: C

This question in 0654/21 May/June 2020

20 Which chemical test does not produce a precipitate? A carbon dioxide and limewater B carbonate ions and dilute hydrochloric acid C chloride ions and aqueous silver nitrate D copper(II) ions and aqueous sodium hydroxide

1 marks

Answer: B

This question in 0654/21 Oct/Nov 2020

21 Substance X is insoluble in water. It reacts with dilute nitric acid to produce solution Y and a gas which turns limewater milky. A white precipitate is formed when aqueous sodium hydroxide is added to solution Y. This precipitate remains when excess sodium hydroxide is added. What is substance X? A calcium carbonate B calcium chloride C zinc carbonate D zinc chloride

1 marks

Answer: A

This question in 0654/22 Feb/March 2021

3 What is the test for the presence of protein in a food sample? A Benedict’s solution B biuret reagent C ethanol emulsion D iodine solution

1 marks

Answer: B

This question in 0654/23 May/June 2021

16 The diagram shows the electrolysis of a compound. switch + – P Q electrolyte When the switch is closed, the solution around electrode P turns orange because a halogen is formed. The positive electrode P is called the ……1……, and the halogen is ……2…… . Which words complete gaps 1 and 2? 1 2 A anode bromine B anode chlorine C cathode bromine D cathode chlorine

1 marks

Answer: A

This question in 0654/21 Oct/Nov 2021

19 Which test and its result identifies aqueous bromide ions? A adding acidified aqueous silver nitrate forming a cream precipitate B adding acidified aqueous silver nitrate forming a white precipitate C adding aluminium foil and heating with sodium hydroxide forming a gas that turns red litmus paper blue D adding dilute acid forming a gas that produces a white precipitate when bubbled through limewater

1 marks

Answer: A

This question in 0654/22 Feb/March 2022

19 Which row shows the flame test colours for lithium and sodium? lithium sodium A lilac blue-green B lilac yellow C red blue-green D red yellow

1 marks

Answer: D

This question in 0654/21 May/June 2022

19 When aqueous potassium hydroxide is warmed with ammonium chloride, a gas is given off. Which test result identifies the gas? A It bleaches pH paper. B It turns anhydrous cobalt(II) chloride blue. C It turns universal indicator red. D It turns red litmus blue.

1 marks

Answer: D

This question in 0654/22 May/June 2022

25 Four watch-glasses contain solid salts as shown. blue white blue pink copper(II) sulfate copper(II) sulfate cobalt(II) chloride cobalt(II) chloride Water is added to each salt. Which statement describes the salt solutions that form? A They are blue or pink only. B They are white or blue only. C They are all pink. D They are all blue.

1 marks

Answer: A

This question in 0654/22 Feb/March 2023

27 During fermentation, an organic liquid and a colourless gas are produced. Which row identifies a use for the liquid and describes the result of a test on the colourless gas? use for the liquid gas test result A monomer in addition polymerisation reactions turns limewater milky B monomer in addition polymerisation reactions relights glowing splint C solvent turns limewater milky D solvent relights glowing splint

1 marks

Answer: C

This question in 0654/22 Feb/March 2023

17 Aqueous potassium bromide reacts with aqueous silver nitrate to produce a cream precipitate. What is the ionic equation for this reaction? A Ag+(aq) + Br–(aq)  AgBr(s) B Ag2+(aq) + 2Br–(aq)  AgBr2(s) C K+(aq) + NO3 –(aq)  KNO3(s) D 2K+(aq) + NO3 2–(aq)  K2NO3(s)

1 marks

This question in 0654/22 May/June 2023

21 Substance X is mixed with aqueous sodium hydroxide. A green precipitate is produced. Which metal ion is present in X? A Cu2+ B Fe2+ C Fe3+ D Zn2+

1 marks

Answer: B

This question in 0654/21 Oct/Nov 2023

3 Which food test requires heating? A fat B protein C reducing sugar D starch

1 marks

Answer: C

This question in 0654/23 Oct/Nov 2023

20 A piece of damp blue litmus paper is put in a test-tube of a gas. The litmus paper turns red and then changes to white. What is the gas? A ammonia B carbon dioxide C chlorine D oxygen

1 marks

Answer: C

This question in 0654/23 Oct/Nov 2023

21 What is used to test for ammonia gas? A a lighted splint B aqueous sodium hydroxide C damp red litmus paper D limewater

1 marks

Answer: C

This question in 0654/22 Feb/March 2024

22 Which metal is used in the test for nitrate ions? A aluminium B copper C magnesium D tin

1 marks

Answer: A

This question in 0654/21 May/June 2024

23 Ammonia is displaced from its salts by reaction with substance Z. Which row identifies substance Z and the test for ammonia? substance Z test for ammonia A hydrochloric acid turns red litmus blue B hydrochloric acid turns blue litmus red C sodium hydroxide turns red litmus blue D sodium hydroxide turns blue litmus red

1 marks

Answer: C

This question in 0654/22 May/June 2024

20 Gas X turns limewater milky. What is X? A carbon dioxide B chlorine C hydrogen D oxygen

1 marks

Answer: A

This question in 0654/23 May/June 2024

8 A student breathed gently in and out of the mouthpiece of the apparatus shown. mouthpiece tube limewater P Q What were the results after 10 breaths? P Q A colourless colourless B colourless milky C milky colourless D milky milky

1 marks

Answer: B

This question in 0654/21 Oct/Nov 2024

25 In a test for water, water turns anhydrous copper(II) … 1 … from … 2 … to … 3 … . Which words complete gaps 1, 2 and 3? 1 2 3 A chloride blue white B chloride white blue C sulfate blue white D sulfate white blue

1 marks

Answer: D

This question in 0654/21 Oct/Nov 2024

20 A student tests an aqueous solution for the presence of sulfate ions. What is the test and observation for sulfate ions? A Acidify the solution and add aqueous barium ions to produce a white precipitate. B Acidify the solution and add aqueous silver ions to produce a cream precipitate. C Add aqueous iron(III) ions to produce a brown precipitate. D Add aqueous copper(II) ions to produce a pale blue precipitate.

1 marks

Answer: A

This question in 0654/22 Oct/Nov 2024

21 What is warmed with a salt to test for ammonium ions? A aqueous barium chloride B aqueous litmus C aqueous silver nitrate D aqueous sodium hydroxide

1 marks

Answer: D

This question in 0654/23 Oct/Nov 2024

27 The results of tests on aqueous G are listed. 1 Adding aqueous sodium hydroxide produces a white precipitate that is insoluble in excess. 2 Adding acidified aqueous silver nitrate produces a cream precipitate. What is G? A calcium bromide B calcium chloride C zinc bromide D zinc chloride

1 marks

Answer: A

This question in 0654/21 Oct/Nov 2025

22 Which row describes the colour changes when water is added to anhydrous copper(II) sulfate and to anhydrous cobalt(II) chloride? copper(II) sulfate cobalt(II) chloride A blue  white blue  pink B blue  white pink  blue C white  blue blue  pink D white  blue pink  blue

1 marks

Answer: C

This question in 0654/23 Oct/Nov 2025