Identification Of Ions And Gases
Overview
Given an unknown white powder or a colourless gas, a chemist can find out exactly what it is using a set of simple, reliable tests. A flame turns a telltale colour, a few drops of a reagent give a coloured precipitate, and a glowing splint reveals a gas. This is the chemistry of detective work.
In this lesson you will learn the flame-test colours of common metal ions, and the tests that identify gases such as hydrogen, oxygen, carbon dioxide, ammonia and chlorine. These tests let you identify substances from the evidence they give.
Objectives
- Describe tests to identify the anions: (a) carbonate, CO₃²⁻, by reaction with dilute acid and then testing for carbon dioxide gas (b) chloride, Cl⁻, bromide, Br⁻, and iodide, I⁻, by acidifying with dilute nitric acid then adding aqueous silver nitrate (c) nitrate, NO₃⁻, reduction with aluminium foil and aqueous sodium hydroxide and then testing for ammonia gas (d) sulfate, SO₄²⁻, by acidifying with dilute nitric acid and then adding aqueous barium nitrate (e) sulfite, SO₃²⁻, by reaction with acidified aqueous potassium manganate(VII).
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Lesson Evaluation
Congratulations on completing the lesson on Identification Of Ions And Gases. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- What flame colour does a sodium ion give? A. Lilac B. Yellow C. Red D. Green Answer: B
- What flame colour does a potassium ion give? A. Yellow B. Lilac C. Orange-red D. Blue-green Answer: B
- How is hydrogen gas identified? A. Relights a glowing splint B. Squeaky pop with a lighted splint C. Turns limewater milky D. Bleaches litmus paper Answer: B
- How is oxygen gas identified? A. Squeaky pop B. Relights a glowing splint C. Turns limewater milky D. Turns litmus red Answer: B
- Which gas turns limewater milky? A. Hydrogen B. Oxygen C. Carbon dioxide D. Ammonia Answer: C
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