Equilibrium Basics and Thermo Equilibrium

The past few weeks in class we have been discussing equilibrium. We have learned that at equilibrium, the forward and reverse reactions are happening at the same time and at the same rate. We learned that the "products" and "reactants" are evenly distributed throughout the container/solution and that they are freely moving. We also learned that brackets denote concentration for the substance in question.

The equation seen above, is a demonstration of how to write a Q equation and a K equation. We learned that Q is the reaction quotient and is is used at any conditions that are not equilibrium. K is the equilibrium expression which is the reaction quotient at equilibrium. When writing this type of expression, you must make sure that it is Reactants/ Products and that if there are stochiometric coefficients they become the exponents. Also we learned that the partial pressures can be used in the same way to find Kp. Make sure that solids and liquids are not included in these quotients, only gases and aqueous solutions are included.

We learned that if Q is larger than K, this means that the reaction is product favored (larger numerator) and to reach equilibrium would have to move to the left (towards the reactants). If Q is smaller than K, the reaction is reactant favored and would move to the right to get to equilibrium.

Le Chatelier's Principle:
Once a system is in equilibrium, a change in temperature, pressure, or concentration of the components will cause the equilibrium to shift to counteract the disturbance.  If more product is added to the reaction system, then the equilibrium will shift away to the products to balance out the extra products. The opposite will happen if more reactant is added, the equilibrium will shift toward the products. Another aspect of this principle is that if the volume is expanded, the equilibrium will shift to increase the pressure. To do this the equilibrium will shift towards the "side" with the most moles. Likewise if the volume is decreased (compressed), the equilibrium will shift towards the "side" with the least moles to decrease the pressure. We learned that the Keq stays the same if volume or concentration are changed.
If there is a change in temperature there will be a change in the Keq value for a reaction. If the reaction is endothermic, and heat is added the equilibrium will shift to the products. This is because heat can be thought of as a reactant for an endothermic reaction. On the other had if the reaction is exothermic adding heat will cause the reaction to shift to the left towards the reactants. This is because heat can be thought of as a product and increasing a product means that it will shift to the reactants (left). When cooling, the endothermic reactions move to the reactants and when cooling an exothermic reaction the equilibrium moves to the products.

Therom Equilibrium
The next thing that we learned about was thermo equilibrium. We already know that if ΔG is positive that the reaction is unfavorable and endothermic and that if ΔG is negative the reaction is favorable and exothermic.We learned that ΔG° has only one value at a given temperature and ΔG has infinite possible values at a temperature. ΔG°=ΔG at standard state conditions of 1.00 atm, 298K, and 22.4L. The equation that we learned to relate ΔG° to ΔG  is ΔG=ΔG°+RTlnQ, where R= 8.314 J/molK and Q is the reaction quotient. To find ΔG°, we learned that ΔG°=-RTlnKeq. So what can we tell from a ΔG° of a system? If the ΔG°  is greater than 0, the reaction at equilibrium is mostly reactants, and if ΔG° is less than 0, the reaction is mostly products at equilibrium. By looking at ΔG, if it is larger than 0 the reaction is non-spontaneous and cannot happen, if it is smaller than 0 the reaction is spontaneous and is moving toward equilibrium from either direction, and if it is = to 0 the system is at equilibrium.

Overall I feel that this material is very confusing and takes a while to grasp understanding. I think that I have a fair amount of understanding about the basic concepts, but I do need to do more of the calculations to prepare for the test. For this reason I would give my understanding a 7/10.