In grade 9, you have learned the basics of stoichiometry, such as moles, molar mass, relative atomic mass and balancing of equation. Here's a quiz and MS to find out how much you have remembered - grade 9 stoichiometry.
Almost everything we know about atoms has been discovered in the past 100 years or so, but it was Democritus who in 400 BCE in ancient Greece came up with the first known model of an atom. He theorised that matter could be cut up into smaller and smaller pieces until a point was reached where it could not be cut up anymore. He called these tiny pieces atomos, which means indestructible in Greek. It was not until the 1950s, however, until atoms were seen for the first time through an electron microscope.
For this lesson, we will be gaining foundational chemistry skills that are essential to understanding basic chemistry.
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Activity: Practice problems
For reading and practice, read from page 241 to 244 and solve questions 11 - 18 in this PDF. Check your answers.
For reading, Kognity 3.2
Balancing equations
Review Reading
Stoich worked example
When doing a chemical reaction, we do not usually add the reactants in the exact amounts needed. Usually, some reactants are in excess and you remove the excess unreacted reactant after the reaction is done. If a reactant is in excess, there is more than enough to react with the other reactants. The other reactants are therefore limiting reagents.
The limiting reagent (or limiting reactant or limiting agent) in a reaction is a reactant that is completely used up when the reaction is finished. The amount of product formed is limited by this reactant, since the reaction cannot continue without it.
Click on Ms. Medley's presentation notes to begin.
Activity: Practice problems
The role of limiting and excess reactants in solving stoichiometry problems. Here's the packet and MS. (Limiting Reactants
Kognity link: 3.3
Mr Marier's Summary Notes on Limiting Reactants + Solution Stoichiometry:
LESSON 3: Reacting gases stoichiometry
Next time you are travelling in a car, think about how the behaviour of gases can affect your journey. From the air pressure in the tyres to the combustion of the hot fuel gases in the engines, gases play vital roles. You hopefully have not experienced another important function that relies upon understanding how gases behave – air bags. When a car is involved in a collision, sensors detect the change in forces and trigger the release of a gas into air bags that inflate in order to cushion and protect the passengers from hitting the structures of the car. The amazing thing is that all of this needs to occur between the start of the collision and the passengers being thrown forward in the car.
Click on Ms. Medley's presentation notes to begin.
Activity: Practice problems
Kognity link: 3.3
The limiting reagent (or limiting reactant or limiting agent) in a reaction is a reactant that is completely used up when the reaction is finished. The amount of product formed is limited by this reactant, since the reaction cannot continue without it.
Click on Ms. Medley's presentation notes to begin.
Activity: Lab
Kognity link: 3.3
LESSON 5/6: Dilutions
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Activity: Practice Problems and Lab
Kognity link: 3.3
accurately make a standard chemical solution of a specified concentration
dilute a standard solution to make a diluted solution.
Useful formula: C1V1 = C2V2
LESSON 7: Percentage yield, purity
Chemical reactions can be summarised by a balanced equation. The number of moles of product formed according to this equation is the theoretical yield. This is because the equation is just a prediction based on what we would expect to occur during the reaction – it is not an exact reflection of what occurs.
Differences from the theoretical equation occur for several reasons. For instance, the reacting substances may obtain impurities, or some of the products may be lost when transferred into another containing vessel, or some product may be lost when separating techniques are applied, or the chemical reaction may not be completed.
The actual yield is the number of moles (or total mass) of a substance obtained experimentally.
The percentage yield of a chemical reaction is the percentage of the theoretical yield that is actually obtained when the reaction is carried out during a controlled reaction
Click on Ms. Medley's presentation notes to begin.
Activity: Practice problems
Mr Marier's Summary Notes on Percentage Yield and Purity
Writing and balancing equation: