Identification of ions by chemical and spectroscopic means (chemistry only): Practice Questions

When silver nitrate solution is added to a solution containing an unknown halide ion in the presence of dilute nitric acid, a cream precipitate forms. Which ion is present?

A chemist is testing an unknown solid using sodium hydroxide solution. The addition of the reagent produces a white precipitate. Upon adding an excess of sodium hydroxide, the precipitate dissolves to form a colourless solution. Which of the following metal ions could be present in the solid?

Which of the following describes why flame emission spectroscopy can be used to determine the concentration of a metal ion in a solution, and not just its identity?

In a laboratory investigation, a student adds silver nitrate solution and dilute nitric acid to an unknown salt solution. A cream precipitate is formed. Which halide ion does this result confirm is present?

What is the correct observation when dilute hydrochloric acid is added to a solid sample containing carbonate ions, followed by bubbling the evolved gas through limewater?

A student is given a solution containing an unknown metal ion. When sodium hydroxide solution is added, a white precipitate forms that dissolves when an excess of sodium hydroxide is added. Identify the metal ion and describe the test for its presence using chemical means.

A sample of a mineral water is analyzed using flame emission spectroscopy. Explain how the resulting line spectrum can be used to determine both the identity and the concentration of multiple different metal ions present in the sample simultaneously.

A student is investigating an unknown white solid, Compound X, which is known to contain a single metal cation and a single anion.

a) The student performs a flame test on Compound X and observes a yellow flame. Identify the metal ion present. (1)

b) To identify the anion, the student dissolves Compound X in distilled water and adds a few drops of dilute nitric acid, followed by silver nitrate solution. A white precipitate forms.
i) Name the anion present in Compound X. (1)
ii) Write the balanced ionic equation, including state symbols, for the formation of this precipitate. (2)

c) A second student suggests using flame emission spectroscopy instead of a flame test to analyze the sample. State two advantages of using instrumental methods like flame emission spectroscopy compared to manual chemical tests. (2)

A student is provided with a colorless solution containing a single unknown ionic compound. To identify the cations and anions present, the student performs a series of chemical tests.

Test 1: A flame test was carried out, which produced a lilac flame.
Test 2: Dilute sodium hydroxide was added to a fresh sample of the solution. No precipitate was formed, but a pungent gas was evolved when the mixture was heated (this gas turned damp red litmus paper blue).
Test 3: Dilute nitric acid was added to another sample, followed by silver nitrate solution. A yellow precipitate was observed.

a) Identify the metal ion responsible for the result in Test 1.
b) Name the anion present in the compound based on Test 3.
c) Write the balanced ionic equation for the reaction that occurred in Test 3, including state symbols.
d) Another student tests a different solution containing iron(III) ions and sulfate ions. Describe the observations expected when adding sodium hydroxide solution and barium chloride solution (in the presence of hydrochloric acid) to this sample.