Preparation Of Salts
Overview
Salts are everywhere in chemistry, from the fertilisers that feed crops to the blue copper sulfate crystals grown in class. Making a pure, dry sample of a salt is a genuine craft, and the method you choose hangs on one question: is the salt you want soluble or insoluble? Get that right and the whole preparation falls into place.
In this lesson you will learn the standard routes to soluble salts, using an acid with an alkali, a metal, an insoluble base or a carbonate, and how precipitation makes insoluble salts. You will use the solubility rules to predict the right method, and learn what hydrated, anhydrous and water of crystallisation mean.
Objectives
- Describe the preparation, separation and purification of soluble salts by reaction of an acid with: (a) an alkali by titration (b) excess metal (c) excess insoluble base (d) excess insoluble carbonate.
- Describe the general solubility rules for salts: (a) s odium, potassium and ammonium salts are soluble (b) nitrates are soluble (c) chlorides are soluble, except lead and silver (d) sulfates are soluble, except barium, calcium and lead (e) carbonates are insoluble, except sodium, potassium and ammonium (f) hydroxides are insoluble, except sodium, potassium, ammonium and calcium (partially).
- Define a hydrated substance as a substance that is chemically combined with water and an anhydrous substance as a substance containing no water.
- [Supplement] Describe the preparation of insoluble salts by precipitation.
- [Supplement] Define the term water of crystallisation as the water molecules present in hydrated crystals, including CuSO •5H O and CoCl •6H O 4 2 2 2.
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Lesson Evaluation
Congratulations on completing the lesson on Preparation Of Salts. 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.
- How is a soluble salt made from an acid and an alkali? A. precipitation B. titration C. adding excess metal D. electrolysis Answer: B
- Which method is used to prepare an insoluble salt? A. titration B. adding excess carbonate C. precipitation D. distillation Answer: C
- According to the solubility rules, which chloride is insoluble? A. sodium chloride B. potassium chloride C. silver chloride D. ammonium chloride Answer: C
- Which sulfate is insoluble? A. sodium sulfate B. barium sulfate C. potassium sulfate D. ammonium sulfate Answer: B
- What term describes a substance containing no water of crystallisation? A. hydrated B. anhydrous C. aqueous D. saturated Answer: B
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