Lesson Notes By Weeks and Term v4 - SHS 2
EQUILIBRIA
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EQUILIBRIA
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Subject: Chemistry
Class: SHS 2
Term: 1st Term
Week: 15
Grade code: 2.1.2.LI.3
Strand code: 1
Sub-strand code: 2
Content standard code: 2.1.2.CS.1
Indicator code: 2.1.2.LI.3
Theme: PHYSICAL CHEMISTRY
Subtheme: EQUILIBRIA
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This lesson explores how the principles of chemical equilibrium and reaction rates are not just theories in a textbook, but are the foundation for large-scale industrial processes that are vital to our modern world and Ghana's economy. We will focus on two cornerstone processes: the Haber Process for making ammonia (the key ingredient for fertilizers) and the Contact Process for making sulphuric acid (one of the most important industrial chemicals). We will learn how chemists and engineers act like economists, balancing scientific principles to get the highest amount of product (yield) in the shortest possible time (rate) at the lowest possible cost.
A. Recap: Le Chatelier's Principle
Before we analyse the industrial processes, we must remember our master rule for equilibrium: Le Chatelier's Principle. Definition: "If a change of condition (like temperature, pressure, or concentration) is applied to a system in equilibrium, the system will shift in a direction that counteracts the change."
Think of it like a balanced seesaw. If you add weight to one side (a change), the seesaw will tilt to balance itself out again (the shift). Effect of Temperature: If a forward reaction is exothermic (releases heat, ΔH is negative), increasing the temperature will shift the equilibrium to the left (favouring reactants) to "use up" the extra heat. A *low temperature* favours the products. If a forward reaction is endothermic (absorbs heat, ΔH is positive), increasing the temperature will shift the equilibrium to the right (favouring products) to "use up" the heat. A *high temperature* favours the products. Effect of Pressure (for gases): Increasing the pressure will shift the equilibrium to the side with fewer moles of gas. Decreasing the pressure will shift the equilibrium to the side with more moles of gas. Effect of a Catalyst: A catalyst increases the rate of both the forward and reverse reactions equally. It helps the system reach equilibrium faster. A catalyst has NO effect on the position of equilibrium (it does not change the final yield).
B. The Haber Process: Manufacturing Ammonia (NH₃)