Monday, January 12, 2015

Even though I dont have a job.... What you need to beef up on for Chem 2 (or how to succeed in Chem II)

Chemistry 2 is that place where all your birds come home to roost.  What that means is that all those ideas and concepts you just managed to retain for the final in Chem 1 are now applied.  In fact, chemistry 2 should really be called Applied Chemistry.  In my humble opinion is should be called Applied Solution Chemistry.

When I talk to students, I describe Chem 1 as "counting atoms". You spend all semester learning various ways to determine how much material you have and then a little bit of time learning about the naming, and electronic stuff that makes atoms do what atoms do, and some of the really cool thermodynamics which tells us what atoms get up to when we arent looking.

The same analysis of almost all of Chem 2 is about what goes on in solutions and the lies we told you in Chem 1.   yes Lies.  Solubility rules.  "All halides are soluble except....." Yeah..no..everything is soluble. It is just a matter of degree. Lets put a number on that!!   THAT is chem 2.  Putting a number on the behavior of chemical reactions.  Usually in solution.

So... to win at Chem II here is a pretty decent strategy.

a) review solutions and solution reactions
start by predicting what the molarity of something is in solution before a reaction and, more critically, how much is left over in solution at the end.  For instance  100.0 mL of a 0.100 M NaOH solution is reacted with 50.0 mL of 0.100 M Acetic acid.   At the end of the reaction there will be 0.050 mol NaOH left, 0.050 of Sodium acetate and close to 0 mol of acetic acid. (note moles not molarity, take into account the dilution too 150 mL now).

This will be the starting point of almost every single reaction you will be looking at in Chem 2

b) review algebra.
almost all of chem 2 is finding an unknown based upon some simple generic algebraic expressions. Particularly working with roots and exponents. Go review the first 3-4 chapters of an algebra book.

c) review thermodynamics
the last few weeks are using ideas from thermodynamics. Procedures for determining enthalpy of reaction from tables and constants will be reused.  (save this for the middle of the semester)

If nothing else... focus on solution behavior.

Oh yeah.. almost anything with a big K is just an equilibrium. (you will learn that about 3-4 weeks in) All you need to keep in mind is WHAT kind of equilibrium ie. a specific way of writing a chemical reaction.