Unit 2: Equilibrium Lesson 4: Predicting Spontaneity

Predicting Spontaneity (Examples) C2H2(g) + 2 Cl2(g) → C2H2Cl4(l) + 386 kJ CH4(g) + O2(g) → CO2(g) + 2 H2O(g) + 394 kJ 4 Au(s) + 3 O2(g) + 162 kJ → 2 Au2O3(s) I do – 10 min

Brain Break!

Le Châtelier’s Principle Consider the following equilibrium reaction: CH3CO2H + H2O ⇌ CH3CO2− + H3O+ Think-Pair-Share: What do you think would happen if CH3CO2H were added to the system? What if we then added H3O+? TPS – 10 min

Le Châtelier’s Principle Is this: “If a closed system at equilibrium is subjected to a change, processes will occur that tend to counteract that change.” In other words, whatever we do, nature tries to undo.

Demo of Le Chatelier’s Principle CoCl42- + 6 H2O ⇌ [Co(H2O)6]2+ + 4 Cl- Predict: What will happen if water is added? What will happen if acetone is added, causing water to be removed? Observe: What happened? Explain: Whatever we do, nature tries to undo! https://ncsu.edu/project/chemistrydemos/Equilibrium/Le%20Chatelier.pdf – 15 min

Homework: Pg. 48 #15 (part iii) and 16 5 min