2.8.14 - Equilibrium

Equilibrium

In class last Monday, we did a Metacognitive lab on equilibrium, that look a little something like this.

(except on it's side).












This showed us that when we add more on one side, the other side increases as well. The graph that would represent these changes would look like this:

Additionally, we spent time on Friday looking at a real experiment with NO2 and N2O4. The NO2 is a brown gas. In this experiment, we saw that adding pressure (or decreasing volume) shifts the equilibrium so that there are less molecules, in this case, more N2O4. When pressure is released, more NO2 forms. So, in our experiment, we saw that adding pressure instantly  makes the gas darker, but becomes lighter because more N2O4 is being formed. When the pressure decreases, the gas instantly becomes lighter, but soon turns darker because more NO2 is being formed. 

In addition to these experiments/metacognitive logs, we worked on three worksheets, Equilibrium 1, 2, and 3. These helped us with the equilibrium constant expressions, how to figure out the constants for different reactions, which way equilibrium shifts, etc.

Main Ideas

I think I'm beginning to understand the concepts. It was difficult at first because I didn't understand what it meant to shift to the product/reactant side, or under what conditions it shifted. I think the ConcepTests really help me because I'm able to think about the question and get immediate results. That way, I can fix my misunderstandings in class, rather than having to think about it, answer the question, think about whether I would get it right or wrong, and then checking back on moodle for answers. I also like taking notes on demos like the two we did this week. To see it visually really helps me understand what's going on. After I work on the equilibrium worksheets, I feel pretty confident with mastering the material :)

1.20.14 - Gasses

Gasses

This is a quick summary of the concepts we kept in mind this week:

Boyle's Law: volume of a fixed quantity of gas at constant temperature is inversely proportional to pressure.

         P1V1=P2V2

Charles's Law: volume is directly proportional to temperature

         V1/T1=V2/T2

Gay-Lussac's Law: Pressure and temperature is directly proportional to pressure

         P1/T1=P2/T2

--->Combined gas law: P1V1/T1=P2V2/T2

Avogadro's Law: volume of gas at constant temperature and pressure is directly proportional to the tnumber of moles (n) in a gas

        V1/n1=V2/n2

---> Ideal gas law: PV=nRT

Standard temperature and pressure (STP)

• 0C and 1.000atm
• 1 mole of gas = 22.4L

Molar Mass: M=m/n  (M=Molar mass, m=mass, n=moles)

         PV=nRT ---> PV=(m/M)RT

Density is mass over volume

         PV=(m/M)RT--->m/v=PM/RT

Effusion

        Grahm's Law of Effusion: r1/r2=Square root of (M2/M1)

Ideal Gasses v. Real Gasses

Ideal gasses are volume-less masses. They ignore attracting/repelling force as well. However, in real gasses, these are all taken into account. 

Corrected ideal Gas equation (+ Van der Waals)

         (P+n^2a/V^2)(V=nb)=nRT

a represents interaction part of molecules. b represents volume component of molecules.

General trends:

• Pressure is usually less than expected
• volume is usually greater than expected
• Ideal: small, nonpolar molecules, high temperatures, low pressure
• Non-ideal: low temperature, high pressure.

In class, we worked on ConcepTests as well as worksheets to become familiar with the concepts.

Main Ideas

I felt it was difficult to understand the different concepts because of the lack of time (at least for me, even though I only lost three days). The white boarding helps me (I think) because I learn best with examples and worked out problems. I also was disappointed because I had to rush through the task chains tonight. I hope you'll have them up again before the test! Other than that, I feel comfortable with the general trends and relationships between volume, pressure, and temperature.