Chemical Formulae, Equations And Calculations
Overview
Chemical equations are the language chemists use to describe what happens during a reaction, and the calculations that follow let you predict exactly how much product you will make from a given amount of reactant. These skills underpin every topic in the rest of the course, from acids and bases to organic chemistry.
This lesson covers word and symbol equations, relative formula mass, the mole concept, reacting mass calculations, percentage yield, empirical and molecular formulae, solution concentrations, and gas volume calculations. Mastering these will give you the quantitative toolkit that Edexcel tests heavily across both Paper 1 and Paper 2.
Objectives
- write word equations and balanced chemical equations (including state symbols): - for reactions studied in this specification - for unfamiliar reactions where suitable information is provided.
- calculate relative formula masses (including relative molecular masses) (Mr) from relative atomic masses (Ar)
- know that the mole (mol) is the unit for the amount of a substance
- understand how to carry out calculations involving amount of substance, relative atomic mass (Ar) and relative formula mass (Mr)
- calculate reacting masses using experimental data and chemical equations
- calculate percentage yield
- understand how the formulae of simple compounds can be obtained experimentally, including metal oxides, water and salts containing water of crystallisation
- know what is meant by the terms empirical formula and molecular formula
- calculate empirical and molecular formulae from experimental data
- understand how to carry out calculations involving amount of substance, volume and concentration (in mol/dm3) of solution
- understand how to carry out calculations involving gas volumes and the molar volume of a gas (24 dm3 and 24 000 cm3 at room temperature and pressure (rtp))
- practical: know how to determine the formula of a metal oxide by combustion (e.g. magnesium oxide) or by reduction (e.g. copper(II) oxide)
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Chemical Formulae, Equations And Calculations. 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 is the relative formula mass (Mr) of sulfuric acid, H2SO4? (Ar: H = 1, S = 32, O = 16) A) 96 B) 98 C) 100 D) 49 Answer: B
- How many moles are in 4.4 g of carbon dioxide, CO2? (Ar: C = 12, O = 16) A) 0.05 B) 0.20 C) 0.10 D) 1.0 Answer: C
- At room temperature and pressure, what volume does 0.50 mol of any gas occupy? A) 6 dm3 B) 12 dm3 C) 24 dm3 D) 48 dm3 Answer: B
- A reaction has a theoretical yield of 25.0 g but only 20.0 g of product is collected. What is the percentage yield? A) 125% B) 80% C) 75% D) 20% Answer: B
- Which of these is the empirical formula of a compound with the molecular formula C6H12O6? A) C6H12O6 B) C3H6O3 C) CH2O D) CHO Answer: C
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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