The Mole Concept
Overview
A balance in a school laboratory can tell you that a strip of magnesium weighs 0.1 g. What it cannot tell you, and what a chemist actually wants to know, is how much magnesium that is in the sense a chemical equation cares about. Equations are recipes written in amounts: two of these react with one of those. Balances are built to read grams. Somewhere between those two facts there has to be a translator, and the mole is it.
This lesson introduces the one unit that lets a laboratory balance speak the language of a chemical equation. You will learn the single sentence the specification uses to define a mole, see why the relative formula mass on a periodic table turns into a weighable quantity the moment you write g after it, and practise moving in both directions between a mass in grams and an amount in moles. By the end you will be able to look at 9.0 g of water and 22 g of carbon dioxide and say, without hesitation, that the two samples hold exactly the same amount of substance.
Objectives
- The relative formula mass of a substance, in grams, is known as one mole of that substance. Students should be able to use the relative formula mass of a substance to calculate the number of moles in a given mass of that substance and vice versa
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 The Mole Concept. 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.
- The relative formula mass of magnesium oxide, MgO, is 40. What is the mass of one mole of magnesium oxide? A. 0.40 g B. 4.0 g C. 40 g D. 400 g Answer: C
- The relative formula mass of copper sulfate, CuSO4, is 159.5. What is the mass of 0.20 moles of copper sulfate? A. 3.19 g B. 31.9 g C. 79.75 g D. 319 g Answer: B
- A sample of sodium has a mass of 4.6 g. The relative atomic mass of sodium is 23. How many moles of sodium are in the sample? A. 0.20 mol B. 0.50 mol C. 2.0 mol D. 5.0 mol Answer: A
- 0.25 moles of a compound has a mass of 10 g. What is the relative formula mass of the compound? A. 2.5 B. 10 C. 40 D. 250 Answer: C
- Four samples each have a mass of 8.0 g. Which sample contains the greatest amount of substance in moles? Relative formula masses: H2O = 18, Mg = 24, MgO = 40, CO2 = 44. A. water, H2O B. magnesium, Mg C. magnesium oxide, MgO D. carbon dioxide, CO2 Answer: A
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 The Mole Concept? 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
