6. Answer to practice problem Le Chatelier 1. When do we use it? 2. Definitions 3. Steps/Rules 4. A solved example 5. A practice problem 6. Answer to practice problem

1. It is used when equilibrium is at stress resulting in a shift to the equilibrium

2. Stress= condition, temperature, volume, pressure A principle that states that a reversible reaction at equilibrium will shift to offset a stress or change in conditions imposed on a system Reversible reaction: the products take part in a separate reaction to reform the reactants

3. Identify the stress Identify how the system will respond the stress Identify how each substance will respond to this change, using the see-saw effect

4. N2(g) + 3 H2(g) ⇌ 2 NH3(g) ΔH = −92kJ/mol If you add N2 or 3H2 the equilibrium will shift to the right If you add NH3 the equilibrium will shift to the left Increase temperature the equilibrium will shift to the left Increase pressure the equilibrium will shift to the side with fewer moles

5. N2(g) + 3H2(g) = 2NH3(g) + 22.0 kcal

6. Stress= Add N2 Equilibrium shift= right N2= stays same H2= decreases NH3= increases K remains the same