1. Relative Atomic Mass
Tutorial – Relative Atomic Mass
At the end of this video, you should be able to
1) Define the term relative atomic mass
2) Explain why some of these masses are not whole numbers
3) Calculate the relative atomic mass from a given relative abundance (Pure chem only)
Why is carbon-12 used as the standard?
Trace the history of how the mass of atoms were determined and why carbon-12 became the standard used for relative masses.
2. Relative Molecular Mass
Tutorial – Relative Molecular Mass
At the end of this video, you should be able to:
1) Define the terms relative molecular mass and relative formula mass
2) Calculate the Mr of various molecules and compounds
3. The Mole and the Avogadro Constant
Mole Day – Avogadro & The Mole
23rd October, is Mole Day – which might put you in mind of small, furry, burrowing animals. However, they don’t even seem to have a commemorative day of any kind; we’re actually talking about the mole in chemistry, a quantity that essentially allows us to ‘count’ atoms and molecules in a more convenient way. This is a fundamental concept, and one that all chemists utilise.
Tutorial – Moles and Masses
At the end of this video, you should be able to apply the equation "no. of moles = mass/molar mass" in a given question.
4. Percentage Composition by Mass
Percentage Composition Tutorial
This lesson demonstrates how to determine the percent composition of a compound by calculating the total mass of each element and comparing it to the total molar mass of the compound.
5. Empirical and Molecular Formulae
Empirical and Molecular Formulae Tutorial
A molecular formula displays the actual number of atoms present in a compound, while the empirical formula is the smallest whole number ratio of atoms.
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This lesson demonstrates how to determine the empirical and molecular formula of a compound given either the mass of the elements or the percent composition.
6. Molar Gas Volume
Molar Volume of Gas
In this video to learn about the molar volumes of gases, how to calculate this and where this knowledge is needed in everyday life.
Note: In O Levels, we usually use r.t.p. (room temperature and pressure) instead of s.t.p. (standard temperature and pressure).
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Error in video: Carbon dioxide is stated as pollutant but it is not a pollutant| Sulphur dioxide should be spelt as sulfur dioxide.
Molar Gas Volume Calculations
This video explains how the molar volume of gases can be used in calculations.
7. Concentration of a Solution
Concentration Virtual Lab
Use the simulation to investigate the following:
• How is concentration of a solution affected by the amount of solute and the volume of a solution?
• What is the difference between a concentrated solution and a saturated solution?
8. Stoichiometric Relationships
Tutorial – Stoichiometric Relationships Part 1
At the end of this video, you should be able to:
1) understand that coefficients represent reacting mole ratios.
2) apply mole ratio to calculate the amount of product formed in a chemical reaction from a given amount of reactant and vice versa.
Tutorial – Stoichiometric Relationships Part 2
This video covers more questions on stoichiometric relationships, including volumetric analysis and applying mole ratio for gases.
9. Limiting Reactants
Making Sandwiches
Create your own sandwich and then see how many sandwiches you can make with different amounts of ingredients. Do the same with chemical reactions. See how many products you can make with different amounts of reactants. Play a game to test your understanding of reactants, products and leftovers. Can you get a perfect score on each level?
Tutorial – Limiting Reactants
In this video, we will learn how to perform chemical calculations using the idea of limiting reactants.
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Three important takeaways about a limiting reactant.
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It is completely used up in a reaction.
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It determines the amount of product formed (the reaction stops when the limiting reagent is all used up)
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It is not necessarily the one that has a smaller number of moles (need compare the mole ratio of reactants)
11. Percentage Yield and Purity
Tutorial – Percentage Yield and Percentage Purity
Through the examples in this video, you will learn to perform chemical calculations to determine the percentage yield of a reaction and the percentage purity of an impure sample.
Gold purity guide
Karat is the term used to measure the gold content or purity. Before we understand the difference between 24k, 22k and 18k gold, you must know what karat stands for. Karat is basically a unit used to measure the purity of gold. The higher the karatage, the purer the gold. Here’s a simple guide to understanding the difference between 24k, 22k and 18k gold.
Test yourself: Calculate the percentage purity of 18k, 22k and 24k gold.
