Lesson Notes By Weeks and Term v4 - SHS 3
MATTER AND ITS PROPERTIES
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MATTER AND ITS PROPERTIES
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Subject: Chemistry
Class: SHS 3
Term: 1st Term
Week: 17
Grade code: 1.1.1.LI.7
Strand code: 1
Sub-strand code: 1
Content standard code: 1.1.1.CS.2
Indicator code: 1.1.1.LI.7
Theme: PHYSICAL CHEMISTRY
Subtheme: MATTER AND ITS PROPERTIES
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Stoichiometry is the heart of chemical calculations. It is like the recipe for a chemical reaction. Just as a cook needs to know how much rice, tomatoes, and oil are needed to make a perfect pot of *jollof rice* for 10 people, a chemist needs to know the exact amounts of reactants required to produce a desired amount of a product. This knowledge is crucial in industries across Ghana, from manufacturing soap and pharmaceuticals to producing fertilizers for our cocoa farms. This lesson will equip you with the skills to quantify chemical reactions, making you a more precise and efficient scientist.
2.1 What is Stoichiometry? Stoichiometry (pronounced "stoy-kee-OM-eh-tree") is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. The foundation of all stoichiometric calculations is a balanced chemical equation. 2.2 The Balanced Chemical Equation: The Recipe A balanced chemical equation gives us two key pieces of information: The substances involved in the reaction. The relative amounts of these substances, represented by coefficients.
Consider the reaction for the Haber process, used to make ammonia for fertilizers: N₂(g) + 3H₂(g) → 2NH₃(g)
This equation tells us: 1 molecule of Nitrogen reacts with 3 molecules of Hydrogen to produce 2 molecules of Ammonia. More importantly, it tells us the mole ratio: 1 mole of N₂ reacts with 3 moles of H₂ to produce 2 moles of NH₃.
This mole ratio is our conversion factor. It allows us to relate the amount of any substance in the reaction to any other substance. Ratio of N₂ to H₂ is 1:3 Ratio of H₂ to NH₃ is 3:2 Ratio of N₂ to NH₃ is 1:2 2.3 The Stoichiometric "Roadmap" Most problems will not give you moles directly. You will be given a mass, volume, or concentration. You must always convert the given quantity to moles before using the mole ratio.