Hi!
Today's agenda:
2 verbal reasoning passages from the Princeton Review
Passage #29, score: 4/7 time: 9:40
Passage #30, score 7/7 time: 8:00
Comment: I feel like I am getting a bit better at these passages finally. A few things I've learned about reading passages...
1.
READ. Reading everyday for a few hours (New Yorker, Economist, etc.) will make you a better reader and more importantly a faster reader. Passages will seem to flow much smoother once you are up to the reading level. Speed and flow is key.
2.
THEME/MAIN IDEA. Every MCAT verbal passage is structured about the same. It goes: Introduction, Body, and Conclusion.
Introduction: This is the first paragraph of the passage and you will ALWAYS be able to know what main idea of the passage just by UNDERSTANDING this paragraph. The rest of the body paragraphs and the conclusion are just to support or refute the claims in this section. KNOW what the main idea is, and know where the author stands if he has an opinion.
Body Paragraphs: Each body paragraph will have its own main idea. It is very important to understand what the purpose of each paragraph is. Most of the time, these paragraphs will hold either support, criticism, or examples. You can get a good idea about each paragraph just from reading the first and last sentences of each paragraph, the middle is usually just details.
Conclusion: This section is used to wrap up the passage with some more interested information about the main idea, or an example to refute the theme or give a different point of view.
The most important parts to know, in my opinion, would be the introduction and the conclusion. At least 2-3 questions will be about information from these sections each passage. For the body paragraphs, if you understand the ideas then you should be able to map out the sections. If a question comes up about body paragraphs, and you are not 100% sure about the answer, you can quickly and efficiently go back to the text to help you answer it. All in all, the verbal section is very difficult to master.
Today's Science Lecture:
CHEMISTRY: EQUILRIUM
Basic concepts:
RATE PROCESSES IN CHEMICAL REACTIONS: KINETICS AND EQUILIBRIUM
1. Reaction rates
- Thermodynamics (dG) describes the spontaneity of a reaction, does not have to do with how fast a reaction occurs. Kinects has to do with the rate at which a reaction occurs.
2. Rate law, dependence of reaction rate on concentrations of reactants
a. rate constant
- only dependent on temperature, all other variables do not change the rate constant
b. reaction order
- dependent on how many variables the rate equation includes. eg.
Rate = K(T) *[x]*[y] would be a second order reaction dependent on x and y
3. Rate-determining step
- Slow step is always rate determining
4. Dependence of reaction rate on temperature
a. activation energy
i. activated complex or transition state
- enzyme can lower the activation energy of a reaction by emulating the transition state of the reaction
ii. interpretation of energy profiles showing energies of reactants and products,
activation energy, ΔH for the reaction
b. Arrhenius equation
- ... K = A*e^(-Ea/RT) aka K = A*e^(-Ea/KbT)
5. Kinetic control versus thermodynamic control of a reaction
- Kinetic control occurs when Product A has a lower activation energy than Product B thus making Product A the kinetic product because this reaction occurs much more rapidly. Product B could possibly have a more stable final product compared to Product A, thus making it the thermodynamic product. Outside pressures acting upon the reaction could effect which product is favored; one example would be temperature.
6. Catalysts, enzyme catalysis
- Speeds up the reaction of an chemical reaction without changing the thermodynamics of the reaction. Catalyst is not used up; remade in the reaction. Lowers the kinetic activation energy hill, thus lowering the activation energy for both the forward reaction and also the backward reaction, thus, speeding up BOTH reactions.
7. Equilibrium in reversible chemical reactions
a. law of mass action
- Equilibrium tends to re-establish itself after outside perturbations
b. the equilibrium constant
- Keq only changes with temperature
c. application of Le Châtelier’s principle
- EQ reestablishes itself after each perturbation.
8. Relationship of the equilibrium constant and ΔGo
- ... dG = - RT ln Keq
