Lesson: Tests for Anions Chemistry

In this lesson, we will learn how to identify aqueous negative ions based on their reactivity and the color and solubility of their salts.

Lesson Plan

Students will be able to

describe the test for halide anions using nitric acid and silver nitrate and explain why acid is used,
identify the colors of the silver halide precipitates,
write word and symbol equations for the precipitation of halide salts,
describe the solubilities of silver halide salts in dilute and concentrated ammonia,
describe the alternative test for halide anions using concentrated sulfuric acid,
describe the test for the sulfate, sulfite, nitrate, and carbonate anion,
write ionic equations for the tests for carbonate, halide, and sulfate anions,
identify the anion in an unknown solution using the tests above.

Lesson Video

Lesson Explainer

Lesson Worksheet

Q1:

A white salt is soluble in water and reacts with hydrochloric acid to produce a colorless gas. When barium chloride is added to a solution of the salt in water, a white solid precipitates. In a flame test, the salt produces a red flame.

What is the name of the metallic element in the salt?

Give the chemical formula of the anion present in the salt.

Q2:

A white salt is soluble in water and produces a red color in a flame test. Addition of silver nitrate to an aqueous solution of the salt results in a yellow precipitate that does not dissolve in concentrated aqueous ammonia. Addition of sodium hydroxide to a solution of the salt has no visible effect, but adding sodium carbonate produces a white precipitate.

Name the anion present in the salt.

Give the symbol of the metallic element in the salt.

Q3:

When barium nitrate is added to a solution of an unknown salt, no precipitate is observed. However, the addition of magnesium nitrate causes a white precipitate to form. Which additional material or reagent could be used to confirm the identity of the anion in the solution?