Chemistry 0620 · IGCSE
Identification of ions and gases
100 practice questions on Identification of ions and gases, with worked solutions and instant marking.
A sample is warmed with aluminium foil in aqueous sodium hydroxide. A gas is given off that changes damp red litmus paper to blue. Which anion is present in the sample?
Feb/March 2016
A substance is warmed with aluminium foil in aqueous sodium hydroxide. A gas is given off that changes damp, red litmus paper to blue. Which anion is contained in the substance?
Feb/March 2016
A student is given an unknown solution. Which two tests give evidence that the solution is copper(II) sulfate?
Feb/March 2017
A student is provided with an unknown solution. Which two tests give evidence that the solution is copper(II) sulfate?
Feb/March 2017
When a solution of compound Z is mixed with aqueous ammonia, a light blue precipitate is formed. This precipitate dissolves in excess of ammonia. A flame test is then carried out on compound Z. What colour is the flame?
Feb/March 2018
When a solution of compound Z is treated with aqueous ammonia, a pale blue precipitate forms. This precipitate then dissolves in excess ammonia. A flame test is carried out on compound Z. What colour is the flame?
Feb/March 2018
The table gives the mass of each ion type in a 100 cm^{3} milk sample.
Feb/March 2018
The outcomes of two tests carried out on an aqueous solution of X are given below. Test: aqueous sodium hydroxide added – a green precipitate formed. Test: acidified aqueous silver nitrate added – a yellow precipitate formed. What is X?
Feb/March 2019
The outcomes of two tests carried out on an aqueous solution of X are shown. What is X?
Feb/March 2019
This question concerns sulfur, sulfur compounds, and water obtained from a sulfur spring. A sulfur spring is a natural water source that contains sulfur.
Feb/March 2019
Salt S is dissolved in water, and three tests are performed on the solution. Identify S.
Feb/March 2020
Salt S is dissolved in water, after which the solution is subjected to three tests. Which substance is S?
Feb/March 2020
If aqueous sodium hydroxide is introduced into a solution containing a metal ion, a grey-green precipitate is produced, and in excess it dissolves to give a dark green solution. Which metal ion is present?
Feb/March 2021
After aqueous sodium hydroxide is introduced into a solution containing a metal ion, a grey-green precipitate is produced, and this then dissolves in excess to give a dark green solution. What is the identity of the metal ion?
Feb/March 2021
A student carries out tests on an unidentified compound M. The compound: - gives a lilac flame in a flame test - gives off a gas that turns limewater cloudy when dilute hydrochloric acid is added. What is M?
Feb/March 2023
An aqueous solution is mixed with a solid. The products formed are an alkaline gas, a salt and water. What are the aqueous solution and the solid?
Feb/March 2023
A student carries out tests on an unknown compound M. The compound: - gives a lilac colour in a flame test - releases a gas that makes limewater turn cloudy when dilute hydrochloric acid is added. What is compound M?
Feb/March 2023
When an aqueous sample of X is warmed with aqueous sodium hydroxide and small pieces of aluminium, a gas is evolved that turns damp red litmus paper blue. If aqueous sodium hydroxide is then added to a different aqueous sample of X, a pale green precipitate is seen. What is X?
Feb/March 2024
What colour change occurs when water is added to anhydrous copper(II) sulfate?
Feb/March 2025
Two salt solutions, P and Q, are examined. The table gives the results. What are P and Q?
Feb/March 2025
Which reagent is used to test for chlorine?
Feb/March 2025
Which ion produces a green precipitate with aqueous sodium hydroxide that then dissolves in excess aqueous sodium hydroxide?
Feb/March 2025
The outcomes from two tests carried out on solid X are shown below. Test: aqueous sodium hydroxide added → observation: a green precipitate was produced. Test: acidified silver nitrate added → observation: a yellow precipitate was produced. What is X?
May/June 2016
These tests are performed on an aqueous solution of salt X. Sodium hydroxide solution is then added, producing a green precipitate that dissolves in excess. Next, a small piece of aluminium foil is introduced into the mixture and the mixture is heated; a gas is released that turns damp, red litmus paper blue. What is X?
May/June 2016
A sample of solution containing substance X was tested, and the findings are given in the table below. flame test: lilac colour acidified silver nitrate solution added: yellow precipitate What is X?
May/June 2016
Which row accurately links the experiment and the observations to the identity of the underlined substance?
May/June 2017
Substance X is warmed with dilute hydrochloric acid, forming a gas that decolourises acidified aqueous potassium manganate(VII). In a flame test, Substance X produces a yellow flame. What is X?
May/June 2017
Dilute sulfuric acid is added separately to two aqueous solutions, X and Y. The results are shown below. Solution X: a white precipitate forms Solution Y: bubbles of a colourless gas are produced Which row indicates the ions present in the solutions?
May/June 2017
A fertiliser in the solid state contains ammonium sulfate. A portion of the fertiliser is mixed with water by shaking. To demonstrate the presence of ammonium ions in the solution, .....1..... is added and the gas given off is tested using damp .....2..... litmus paper. Which words complete gaps 1 and 2?
May/June 2017
Three different experiments are performed using a solution of substance X. What type of substance is X?
May/June 2017
Aqueous sodium hydroxide reacts with an aqueous solution of compound Y to produce a green precipitate. Aqueous ammonia also reacts with an aqueous solution of compound Y to produce a green precipitate. In both reactions, the precipitate remains insoluble in excess reagent. Which ion is present in Y?
May/June 2017
A farmer accidentally puts two substances into the soil at the same time. They react with each other to produce a gas that turns damp red litmus paper blue. Which two substances are they?
May/June 2017
When substance X is treated with warm dilute hydrochloric acid, it gives off a gas that decolourises acidified aqueous potassium manganate(VII). In a flame test, substance X produces a yellow flame. What is X?
May/June 2017
When aqueous sodium hydroxide is added to an aqueous solution of compound Y, a green precipitate is formed. Aqueous ammonia likewise gives a green precipitate when it is added to an aqueous solution of compound Y. In both tests, the precipitate remains insoluble if excess reagent is added. Which ion must be contained in Y?
May/June 2017
The table presents the ions found in a $1000\text{ cm}^3$ portion of polluted river water.
May/June 2017
The table presents the ions found in a $1000\,\text{cm}^3$ rainwater sample.
May/June 2017
The table lists the ions found in a 1000 cm^{3} sample of mineral water.
May/June 2017
X and Y are two salt solutions that are tested. The results are shown in the table. What are X and Y?
May/June 2018
Which two gases produce the same outcome in the test illustrated?
May/June 2018
Two separate tests are carried out on separate solutions of compound X. 1 When aqueous sodium hydroxide is added, a green precipitate is produced and this dissolves in excess aqueous sodium hydroxide. 2 When dilute nitric acid and aqueous silver nitrate are added, a white precipitate is formed. What is compound X?
May/June 2018
A white crystalline solid is dissolved in distilled water. A small quantity of dilute nitric acid is then added, followed by aqueous silver nitrate. There is no visible change. What may be inferred about the white crystalline solid?
May/June 2018
The solubility of several salts is given. Which pair of aqueous solutions will form an insoluble salt when combined?
May/June 2018
The outcomes of two tests carried out on a solution of compound Q are shown. What is Q?
May/June 2019
A blend of two substances, R and S, is heated. The moist red litmus paper changes to blue. What are R and S?
May/June 2019
A substance is examined using three different reagents. Which row gives the outcomes obtained with aqueous iron(II) nitrate?
May/June 2019
A solution of compound X is tested in two different ways. The observations are shown. What is X?
May/June 2019
Which gas is given off when ammonium chloride is heated with aqueous sodium hydroxide?
May/June 2019
Three metal compounds, P, Q and R, are heated with a Bunsen burner. The observations are given below. P: a colourless gas is given off, which relights a glowing splint Q: a colourless gas is given off, which turns limewater milky R: no change occurs Which row identifies P, Q and R?
May/June 2019
This question concerns iron and compounds of iron.
May/June 2019
Ammonium chloride is warmed with aqueous sodium hydroxide. A gas is given off which turns damp universal indicator paper blue. Which gas is this?
May/June 2021
Which test is the correct one for the named gas?
May/June 2021
Three tests are carried out in order to identify the ions in aqueous solution X. Which ions are contained in X?
May/June 2021
A white solid, J, is examined and the observations are given below. Flame test: a red flame. Acidify with nitric acid and then add aqueous silver nitrate: a white precipitate. What is J?
May/June 2021
A white solid Z reacts with dilute hydrochloric acid and gives off a gas. The identical gas is also formed when compound Z is heated strongly. What is Z?
May/June 2021
Data on the solubility of salts is given. Which two compounds would form a precipitate when their aqueous solutions are mixed?
May/June 2021
The table displays the masses of certain ions present in 1000 cm$^3$ of fruit juice.
May/June 2021
The table lists the masses of several ions in $1000\,\text{cm}^3$ of fruit juice.
May/June 2021
Three individual samples of aqueous compound T are examined. The test results are given. What is T?
May/June 2022
Aqueous solutions that contain copper(II) ions may be recognised by carrying out flame tests and by adding aqueous sodium hydroxide. Which row gives the observations made in these tests?
May/June 2022
Which ion produces a precipitate that dissolves in excess in both aqueous ammonia and aqueous sodium hydroxide?
May/June 2022
Sulfur dioxide is tested by reacting it with acidified potassium manganate(VII). What colour change is observed in this test?
May/June 2022
Acidified aqueous silver nitrate is added to a test tube that contains aqueous chloride ions. The test tube is then placed in direct sunlight. Which row gives the observations and explains what occurs to the reaction mixture?
May/June 2022
Three metal compounds, J, K and L, are warmed with a Bunsen burner. The observations are as follows. J: a colourless gas is given off, and it relights a glowing splint K: a colourless gas is given off, and it makes limewater turn milky L: no change Which row correctly identifies J, K and L?
May/June 2022
Which of the following statements about sulfur dioxide are correct? 1. Sulfur dioxide decolourises acidified potassium manganate(VII). 2. Sulfur dioxide is produced when acids react with carbonates. 3. Sulfur dioxide is used as a bleaching agent. 4. Sulfur dioxide can be used to treat acidic soil.
May/June 2022
Which ion gives a precipitate that dissolves in excess with both aqueous ammonia and aqueous sodium hydroxide?
May/June 2022
Three metal compounds, J, K and L, are heated with a Bunsen burner. The outcomes are shown below. J: a colourless gas is given off that relights a glowing splint. K: a colourless gas is given off that turns limewater milky. L: no reaction occurs. Which row identifies J, K and L?
May/June 2022
The table lists the masses of several ions in a 1000 cm$^3$ toothpaste sample.
May/June 2022
The table gives the masses of certain ions in a $1000\text{ cm}^3$ toothpaste sample.
May/June 2022
The table gives the masses of several ions in a 1000 cm$^3$ toothpaste sample.
May/June 2022
Two separate tests were carried out on a white solid sample X. Test: dilute nitric acid is added Observation: fizzing occurs Test: aqueous sodium hydroxide is added and the mixture is warmed Observation: a gas is produced which turns damp red litmus paper blue What substance is X?
May/June 2023
A wax candle is produced from a blend of hydrocarbons. The candle is then ignited and put inside a gas jar together with a strip of cobalt(II) chloride test paper, as shown. Soon afterwards, the oxygen in the jar is exhausted and the candle flame extinguishes. Which substance is detected by the cobalt(II) chloride paper?
May/June 2023
If acid is added to salt X, a gas is given off that makes limewater turn milky. If sodium hydroxide is added to salt X, a gas is given off that turns litmus paper blue. What is X?
May/June 2023
If acid is added to salt X, a gas is formed that turns limewater milky. If sodium hydroxide is added to salt X, a gas is released that turns litmus paper blue. What is X?
May/June 2023
Which reaction mixture would form a precipitate?
May/June 2023
A salt, S, is added to water and the resulting solution is tested in three ways. What is the identity of S?
May/June 2024
An aqueous solution of compound M is examined. The observations are as follows: the flame test gives a lilac colour; adding acidified barium nitrate produces a white precipitate. What compound is M?
May/June 2024
Which reaction results in the formation of a white-coloured substance?
May/June 2024
Two tests are performed on substance Z. test 1 When a flame test is done, a red flame is seen. test 2 Substance Z is dissolved in water, then dilute nitric acid is added, followed by aqueous silver nitrate. A yellow precipitate is formed. What is substance Z?
May/June 2024
A substance is examined using three different reagents. Which row gives the results obtained with aqueous iron(II) nitrate?
May/June 2024
A student performs a flame test on a sample. The flame appears light green. Which ion is present in the sample?
May/June 2024
Name any two aqueous solutions that, when combined, give a precipitate of barium sulfate.
May/June 2024
A blend of two substances, R and S, is warmed gently. The moist red litmus paper changes to blue. Which substances are R and S?
May/June 2025
Separate samples of four different aqueous metal nitrates are each examined using aqueous sodium hydroxide, dilute sulfuric acid and a flame test. Which row gives the correct collection of results for the named aqueous metal nitrate?
May/June 2025
Four separate colourless solutions are each examined individually with aqueous sodium hydroxide and with acidified aqueous silver nitrate. Which row gives the results for sodium chloride?
May/June 2025
The three compounds are aluminium nitrate, ammonium chloride and ammonium nitrate. Each compound is heated with aqueous sodium hydroxide. Which of the compounds will produce ammonia?
May/June 2025
The table gives the outcomes of two different tests carried out on a sample of aqueous T. Flame test: gave a yellow flame. Add dilute nitric acid: effervescence. What is T?
May/June 2025
A farmer accidentally places two substances into the soil at the same time. They react together and produce a gas that changes damp red litmus paper to blue. Which two substances are they?
May/June 2025
This question concerns sea water and the substances present in sea water.
May/June 2025
Four substances, P, Q, R and S, are examined as shown. Identify P, Q, R and S.
Oct/Nov 2016
A combination of two substances, X and Y, is heated. A piece of damp red litmus paper changes to blue. What are X and Y?
Oct/Nov 2016
In the experiment illustrated, a white precipitate appears in the limewater. What do X and Y represent?
Oct/Nov 2016
Aqueous sodium hydroxide was added gradually, and then in excess, to the separate solutions of W, X, Y and Z. The outcomes are shown. Which row shows the metal ions present in the solutions?
Oct/Nov 2016
A sample of fertiliser is treated with aqueous sodium hydroxide and the mixture is warmed. Ammonia gas is released. Which ion is present in the fertiliser?
Oct/Nov 2016
Compound T is placed into dilute hydrochloric acid and the mixture is warmed carefully. A gas is produced that changes acidified aqueous potassium manganate(VII) from purple to colourless. When compound T is tested in a flame, a lilac flame is observed. What is compound T?
Oct/Nov 2016
The diagram illustrates the production of a gas, G, through four reactions, starting from glucose or from a solid, S. What are the formulae of gas G and solid S?
Oct/Nov 2016
Four substances, P, Q, R and S, are examined as follows. Test results: - On adding dilute hydrochloric acid: - P: a gas is released which ‘pops’ with a lighted splint - Q: a gas is released which turns limewater milky - R: no change - S: no change - On adding dilute aqueous sodium hydroxide and warming gently: - P: no change - Q: no change - R: a gas is released which turns damp red litmus paper blue - S: no change Which substances are P, Q, R and S?
Oct/Nov 2016
Aqueous sodium hydroxide was added drop by drop, and then in excess, to separate solutions of W, X, Y and Z. The outcomes are shown. Which row identifies the metal ions in the solutions?
Oct/Nov 2016
When compound T is put into dilute hydrochloric acid and heated gently, it releases a gas that decolourises acidified aqueous potassium manganate(VII), changing it from purple to colourless. A flame test on compound T gives a lilac flame. What is compound T?
Oct/Nov 2016
The bar charts show the concentrations of the principal ions in two seawater samples, sample A and sample B.
Oct/Nov 2016
A scientist examined which substances were present in a $1\,\text{dm}^3$ river-water sample from an agricultural district. The table lists the mass of each ion dissolved in the $1\,\text{dm}^3$ sample.
Oct/Nov 2016