Chemical Formulae, Equations And Calculations
Overview
Chemical equations are the language of chemistry. Every reaction, from rusting iron to baking bread, can be described precisely using formulae and balanced equations. Being able to write, balance, and calculate from equations is one of the most essential skills in the entire IGCSE course.
In this lesson you will learn how to write word and balanced symbol equations with state symbols, calculate relative formula masses, work with moles, find reacting masses and percentage yield, and determine empirical and molecular formulae from experimental data. These calculations appear on every exam paper.
Objectives
- Write word equations and balanced chemical equations (including state symbols)
- Calculate relative formula 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 and relative formula mass
- Calculate reacting masses using experimental data and chemical equations
- Calculate percentage yield
- Understand how the formulae of simple compounds can be obtained experimentally
- Know what is meant by the terms empirical formula and molecular formula
- Calculate empirical and molecular formulae from experimental data
- Know how to determine the formula of a metal oxide by combustion or by reduction
Lesson Note
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.
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 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 4.0 g of sodium hydroxide, NaOH? (Mr = 40) A) 0.01 B) 0.10 C) 1.0 D) 4.0 Answer: B
- Which state symbol represents a substance dissolved in water? A) (s) B) (l) C) (g) D) (aq) Answer: D
- A compound has the empirical formula CH2O and a relative formula mass of 60. What is the molecular formula? A) CH2O B) C2H4O2 C) C3H6O3 D) C6H12O6 Answer: B
- A reaction has a theoretical yield of 20 g and an actual yield of 15 g. What is the percentage yield? A) 25% B) 50% C) 75% D) 80% 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.
Practice Mock Questions
Want to practice mock questions on Chemical Formulae, Equations And Calculations? 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
