In this post, you will find a summary of all the mole concept and stoichiometry formulae you’ll need for your O Level Chemistry exams.
1. Converting number (of particles e.g. ions, atoms, molecules ,etc) to number of moles
number of particles = Avogadro’s Constant x number of moles
where Avogadro’s Constant = 6.02 x 1023
2. Converting mass to moles
moles = mass / molar mass
3. Converting volume of gas to moles
moles = volume of gas / molar volume
where molar volume = 24 dm3 at room temperature and pressure (r.t.p)
4. Converting concentration of solution to moles
moles = concentration (in mol/dm3) x volume (dm3)
5. Converting between different units of concentration g/dm3 to mol/dm3
concentration (g/dm3) = concentration (mol/dm3) x molar mass
6. Finding mass from concentration (in g/dm3)
mass (g) = concentration (g/dm3) x volume (dm3)
7. Stoichiometry Rules
The number (or coefficient) in front of each compound or element in a balanced equation represent the mole ratio required for the reaction. If there is no number in front of the element or compound, then it is 1.
Let’s use the equation below as an example:
2HCl + Ba(OH)2 –> BaCl2 + 2H2O
Based on the equation above, it tells us that the stoichiometry ratio of HCl to Ba(OH)2 in the reaction is 2:1. This means that 2 moles of HCl will react with 1 mole of Ba(OH)2 . If 0.3 moles of HCl is used, then 0.15 mole of Ba(OH)2 is needed for the reaction.
Key concept: Chemical reaction gives us the mole ratio of the reactants and products.
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In this course, students will learn the chapters on atomic structure, chemical bonding, elements, molecules and compounds, and also the fundamentals of chemistry – writing equations, and chemical formulae. Check out this course here.
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In this course, students will learn acids, bases and salts, qualitative analysis, metals, periodic table and ammonia. I also share a way of remembering the metals in the reactivity series in this course. You can get this on-demand course here.
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Questions on mole concept and stoichiometry can be combined with any other chapter. In this course, I will go through with you step- by-step all the concepts you need to know for mole concept and stoichiometry. You can get this on-demand course here.
4. Rate of reaction (reaction kinetics) and heat of reaction (enthalpy change of reaction)
These topics involve applying concepts learnt to scenario-based questions. In our on-demand course on the rate of reaction and heat of reaction, we go through the concepts and how to apply them to questions. You can get this on-demand course here.
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Learn redox reactions, and electrolysis and electric cell n this on-demand course here. Most schools cover electrolysis last, so if you want to learn ahead of your school, check out our course here.
In O Level Chemistry, students are expected to know the properties, and reactions of alkanes, alkenes, alcohols, carboxylic acids, esters and polymers (addition and condensation polymers). We talk about them in detail in our on-demand course on O Level Organic Chemistry. You can get this on-demand course here.