Preparation Of Salts
Overview
Somewhere in the building you are sitting in there is almost certainly a tub of Epsom salts, a bottle of iron tablets, a bag of blue crystals for treating a pond or a sack of micronutrient for a field. Every one of them is a salt, and every one of them was made on purpose by a chemist who began with a bottle of acid and had to answer one practical question before anything else: what am I going to let that acid attack? The answer chooses the apparatus, decides how long the afternoon takes, and settles whether the product arrives as a dish of grown crystals or as a contaminated mess.
This lesson gives you the whole decision and then walks each branch of it in detail. You will learn the three partners an acid can be offered, why a route that works beautifully for copper would be dangerous for sodium, the reason chemists deliberately add too much of one reactant and then throw the leftovers away, why an indicator has to be used once and then carefully left out, and the patient technique that turns a colourless solution into a dish of grown crystals. By the end you will be able to plan a preparation for a salt you have never made, which is precisely what the examiner asks you to do.
Objectives
- Soluble salts can be made from acids by reacting them with: metals - not all metals are suitable; some are too reactive and others are not reactive enough; insoluble bases - the base is added to the acid until no more will react and the excess solid is filtered off; alkalis - an indicator can be used to show when the acid and alkali have completely reacted to produce a salt solution. Students should be able to suggest methods to make a named soluble salt.
- Salt solutions can be crystallised to produce solid salts.
Mind map
This topic is mapped out so you can see how the ideas connect.
Open the mind map in the app
Lesson Note
Complete Note Available on the Green Bridge App
Get the Green Bridge CBT app on your phone or computer for the complete IGCSE library: past papers, mark schemes, mind maps, flashcards and audio lessons.
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.
- Which salt is produced when copper(II) oxide reacts with dilute nitric acid? A. copper(II) nitrate B. copper(II) sulfate C. copper(II) chloride D. copper(II) hydroxide Answer: A
- A student adds excess magnesium oxide to warm dilute hydrochloric acid, then filters the mixture. What is present in the filtrate? A. magnesium oxide only B. magnesium chloride solution C. hydrochloric acid only D. solid magnesium chloride Answer: B
- Which metal cannot be used with dilute sulfuric acid to prepare its sulfate, because it is not reactive enough to react with the acid? A. magnesium B. zinc C. iron D. copper Answer: D
- Why is an indicator used when potassium nitrate is prepared from potassium hydroxide solution and dilute nitric acid? A. Potassium nitrate is insoluble in water. B. Potassium hydroxide dissolves, so an excess of it cannot be filtered off. C. Nitric acid does not react with potassium hydroxide. D. The reaction produces a gas that must be measured. Answer: B
- A salt solution is to be crystallised. What should be done to it? A. Boil it until it is completely dry. B. Filter it and keep the residue. C. Evaporate some of the water, then leave it to cool slowly. D. Add more water and leave it to cool slowly. Answer: C
Work through these questions in the app
Work through these questions in the app
Recommended Books
Practice Mock Questions
Want to practice mock questions on Preparation Of Salts? Download the Green Bridge CBT app to access mock questions and full practice assessments for this topic.
Download The App On Google Playstore
Everything you need to excel in your exams
