Weekly Blog Post 2/3-9

This week we were learning equilibrium. We spent most of the week either doing calculations or doing ConcepTests, both of which are very helpful. Equilibrium is a fairly simple concept, and for me hasn't been too hard to understand. LeChatalier's principle is a fundamental principle when it comes to equilibrium, and it says that if you change a reaction in some way, it will always try to come back to equilibrium. For example, if you have the reaction A+2B<--->3C, and you add more A to the reaction, the reaction will shift towards the product to balance it. The same works for pressure. If the reaction was put under higher pressure, the pressure wouldn't shift in this case because there are equal numbers of moles on each side of the equation. However, if there were four moles of C rather than three, the reaction would shift towards the reactants because there would be a higher pressure in the products, C, that needed to be balanced out. The unit K tells us the equilibrium constant for a reaction, and can either be Kc or Kp depending on whether we are measuring pressure or concentration of the reactants/products. To calculate these we would divide the concentration/partial pressures of the products by those of the reactants at equilibrium to find the value for K. Here is a good website for calculating K. There is also the letter Q which represents the K value for any specific point during a reaction not at equilibrium, calculated in the same way. 

(I accidentally pressed the quote button and that's why it's indented like this... don't know how to fix it. Sorry about that.)

We also did a great demo with a syphon and two graduated cylinders that visually represented the equilibrium process very well. When more of the liquid was added to one cylinder, it went through the syphon to the other "side" and came to equilibrium when the two water levels were at the same height. The demo was pretty helpful in explaining the basics of equilibrium.

I think my grasp of the concepts we learned this week is pretty solid, but I have a feeling the hard parts are just beginning so I need to stay on top of the material we have now so I don't fall behind for the next week. Other than that, I have really enjoyed equilibrium.

Last week we began our gas law unit. We started with ideal gasses and how they behave. We worked a lot with the ideal gas law, PV=nRT where P= pressure in atmospheres, V=volume in litres, n=number of moles, R=.0821 or the universal gas constant, and T=temperature in degrees kelvin. Derived from this ideal gas law equation are five other gas laws, named after the scientists who contributed to them. Gay-Lussac's law states that pressure and temperature are directly related through the relationship P1/T1=P2/T2. Charles' law states that volume and temperature are directly related through the relationship V1/T1=V2/T2. In Boyle's law, volume and pressure are inversely related, P1V1=P2V2. Dalton's law says that you can add partial pressures to get the total pressure. Avogadro's law states that volume and number of particles are directly related, V1/N1=V2N2. If you combine Gay-Lussac's Charles' and Boyle's laws, then you get the combined gas law, (P1V1/T1=P2V2/T2) which is good to remember because there's no need to remember the individual other laws, just cover up the constant and you have the equation you need.

I understand ideal gasses pretty well, sometimes the math can be a bit confusing, but only the stoich parts.

Real gasses take into account the attractiveness of particles to each other, and also their volume. If the particle is bigger, it will make the total volume bigger and also it will be more polarizable, making the pressure go down due to the particles pulling themselves from the walls. The volume for ideal gasses is adjusted up by a and the pressure for ideal gasses is adjusted down by b due to these phenomena.

I understand gas laws pretty well, but not perfectly. I still have work to do. My major problem with any test has seemed to have been the math part, so I need to get some extra practice with that tonight and tomorrow.