Gen chem recap email

1. (pg 4, email): -How is Grahm’s Law a rearrangement of Avg KE α Temp?

Consider that at the same temperature, two gases have the same KE.  That means KE1 = KE2, or m1(v1^2) =m2(v2^2).  We can rearrange that to m1/m2 = (v2^2)/(v1^2).  Taking the square root of both sides, we have sqrt(m1/m2)=(v2/v1).  "Rate" is another term for velocity, so we have Graham's Law.

-Why doesn’t mass affect average KE as well?
As mass increases, velocity decreases so that we have the same KE.

2. [pg 4, email, van der Waals eqn of state(Real Gases)]: How are “real pressure lower than expected due to attractive forces”? Are these pressures referring to pressure exerted by gas?

Real pressure refers to the pressure exerted by the gas, yes.  When the gas particles are attracted to each other, they no longer occupy as large a volume (their attracton pulls them close to each other).  Thus, with reduced volume, they are no longer pushing as hard on the walls of the container.  They are exerting a smaller pressure.

3. (pg 4, email vdW state of Real Gas): How are you discerning these trends of volume from the graph in the email? In class, I think the axes were flipped.

I did present it another way in class, but consider that pressure is the x axis here (and thus not really affecting our Y-axis), R and T are constants, and so the only variable we're really affecting in the y-axis is volume.  This shows us that predicted volume is below 1 and then above 1 (i.e., below predicted, and then above predicted) as we increase pressure to higher and higher levels.

                    
                  -What pressures are you modulating (the x-axis); is it the pressure of gas or of the container?
This is the pressure created by the container.