More gen chem questions

1. (pg 57, Lesson Book): Would you post the definition for an informational passage (e.g. structure, content, etc.), the things to notice (either for our maps or in general), and the common types of MCAT questions which follow? Similarly, could you respond to the previous question for the other two passage types? [Although you stated them in class, I wanted to have a clear approach to each equation type]

Informational - presents info like a textbook; look for variable relationships, new terms, new definitions.  Questions tend to focus on variable relationships or utilizing the new terms.
Experimental - presents at least one experiment and its results.  Look for:  who did it, what are they trying to show, what did they measure, if there's more than one experiment, what are the differences, and if they make a mistake, what is it.  Questions usually involve applying the experimental information or doing calculations.
Persuasive Argument - presents explanations for a phenomena by more than one person.  Focus on the differences between arguments.  Questions are verbal-like (strenghten/weaken).

1. -When the s-orbital electron in Cr (in its electron configuration) is promoted to the d-orbital, is this called half-stability of subshell or orbital?
2. Stability of the subshell (s, p, d, and f are subshells).

2. (pg 58, Lesson Book): How did you know the passage is informational just from scanning? Why wouldn’t it be persuasive, since two separate models (quantum numbers vs. Bohr)?

Lots of new formulas --> informational.  And because it doesn't really contrast the models.

3. (pg 58, Lesson Book, Map): Don’t you need a descrtiption of each eqn, since it seems that the Eq1 Energy= Eqn3 Energy?

Why would you?  They both depend on the same things, so they work on the questions.

1. -Just from reading the passage initially, this equating of the two is not clear? Do we not care about this?

You're going too far with the passage.  Take it at face value.  If they ask you to compare them, look at their descriptive text (one is for Hydrogen only, the other is for any one-electron system).  Focus on relationships in the equations, not extraneous details.

4. (pg 57, Lesson Book, Map): When you state contrast keywords indicate where the author will change scope, what do you mean? Do you think of “scope” as the implicit portion of the paragraph, e.g. Kinematics for Airbag example as we saw in a previous class?

No, "scope" is what they're focusing on.  First, I'll focus on reaction time in safety, then I'll focus on seatbelts, then airbags.  This is a change in scope.

5. (pg 58, Lesson Book, Map Eq#3): If in Eq#3 you include the negative when you break the eqn into two proportionalities, then if a questions asks if you double Z and (1/3)n, wouldn’t the negative sign mistakenly be counted twice?

Nope.  The proportionality still holds.  In both cases, it's proportional to the NEGATIVE value.

6. (pg 58, Lesson Book): How short should paragraph maps be? What kind of keyword is “further” (located above Eq3)? Is it continuation is it more like the words furthermore or thus, i.e. a conclusion keyword?

Depends on how much new info is presented.  In general, short and sweet is how you want to go.  Further is continuation, but since they've set up three contrasting equations, we want to look at each of them.

7. (pg 58, Lesson Book): When you excite an electron, do you excite it into another shell (different n-value) or to a different subshell? When think of the notion that electrons at a lower principal quantum have lower energies do you rationalize it as electrons close to the positive nucleus make it lower in energy?

Could be to either a different shell or subshell.  And yes, think of it like gravitational potential energy.  The close it is to the middle (nucleus or Earth), the lower the energy.

8. (pg 58, Lesson Book): -When you go down a period Zeff↓, and the explanation that you had given had to do with electron-shielding effect. Wouldn’t the gain in protons and the subsequent gain of electrons neutralize this effect?

Valence electrons do NOT shield each other, so adding more protons increases the pull on each valence electron, and they can't block/shield for each other.

1. -How would you explain the following atomic radius trend: Cu>Ni>Cr? Also, why is the atomic radius of Zn > Cu?
2. Outside the scope of the MCAT.  They care about trends, not all the exceptions.  This is especially true for periodic trends.

9. (pg 64, Lesson Book, Critical Thinking): Why does sulfur have a greater release of energy (i.e. greater electron affinity) than both Si and P?

 Sulfur is the furthest to the right, so this follows our trend.  It is very happy picking up extra electrons because it "loves on" its electrons the most (greatest Zeff).  Thus, it has the greatest release of energy.

1. -In class, you had stated there are two places where you find positive EA values (i.e. energy needs to be added for addition of electron), These two places should be Group IIA and Group 8A (Noble Gases), correct?
2. Group IA and Noble Gases, not IIA.

10. (pg 66, Lesson Book): Why is HCl considered polar covalent as opposed to ionic?

These are both nonmetals, and nonmetals tend to make covalent bonds.  Also, the difference in electronegativity just isn't quite large enough to consider it ionic.

11. (pg 70, Lesson Book): What is the topic and scope of the passage?

Topic:  Chemical complexes
Scope:  Their chemistry, geometry, and general aspects

12. (pg 70, Lesson Book): When mapping, what do you ask yourself after reading each sentence to comprehend and make the most of the passage or sentence (i.e. to avoid glazing)?

Ask yourself, "do I need this?" and, if so, "what did this say?"

13. (pg 71, Lesson Book, #6): -How do you compare based on Charge and what would be the Total charge of each? If you do it as the passage does it (i.e. just look at the first ion), then the answer is different then correct answer?

Total charge, it says, is "of the species present (as absolute values)

Looking at the answers choices:

[Co(NH3)6]PO4 --> [Co(NH3)6]3+ + (PO4)3-.  Charges are +3 and -3.  As absolute values, |3|+|-3|=6
Na3[CoCl6] --> 3Na+ + [CoCl6]3-.  Charges are 3 atoms charged +1 and one charged -3.  As absolute values, 3|1|+|-3| = 6
[Cr(NH3)4Cl2]Cl --> [Cr(NH3)4Cl2]+ + Cl-.  Charges are +1 and -1.  As absolute values, |1|+|-1| = 2
[Cr(NH3)5Cl]SO4 --> [Cr(NH3)5Cl]2+ + (SO4)2-.  Charges are +2 and -2.  As absolute values, |2|+|-2| = 4 

1. -If you do it your way of Absolute Tot Charge, then answer choices A & B would be tied with +6charge. Plaease note that I understand your rationale for the # if ions approach.
2. Yes they would be tied.  But there's another criteria -- the number of ions.  And B definitely beats A for that.

14. (pg 73, Lesson Book, Charles’ Law, Graph of V vs. T that you drew on Board): -How would ↑Temp then ↑Volume, when a gas tries to occupy the volume of its container?

Assume a non-rigid container, like a balloon.  Increased temp will increase the volume of the balloon.

15. (pg 74, Lesson Book, 1^st Critical Thinking): -In class you said that an alternative way to answer the question would be is to see that if you double each of the number of moles of gas, then you get their partial pressures as well. Why and could you explain?

If there is a 1:1:1/2 ratio for the number of moles of gas, and they're all ideal gases, then we know that they'll pressures that also adhere to this ratio at the same temperature.  Thus, since we know that the total is 5 atm and because 2:2:1 is the same ratio as 1:1:1/2, then we can say that their pressures are 2 atm, 2 atm, and 1 atm respectively (that adds up to 5 atm!)

16. (pg 74, Lesson Book, 2^nd Critical Thinking): Is Grahm’s Law used for effusion or diffusion? IS the second critical thinking question an example of diffusion?

Both.  The second question is diffusion, yes.

17. (pg 76, Lesson Book, passage): What is the independent variable pressure or volume?

Neither is independent.  They both depend on the amount of mercury the student added.  It probably the most sense, though to have pressure be the X-axis, for purely conventional reasons.

18. (pg 77, Lesson Book, Q#9, Answer Choice II): Why would or how would you explain why CO₂ has stronger attractive forces than He (since CO₂ has not net dipole)?

It's bigger, and will therefore have more dispersion forces as well as more gravitational pull between molecules.

1. -In general, what would you do (or does it even happen) where the idea of am answer choice is correct (i.e. attractive forces) but the logic doesn’t apply for the specific case used?

Well, then it can't be the answer.

2. (Answer Choice I): usually pressure of a gas is affected by a volume of container and not gas (i.e not gas molecules pushing on other gas molecules)? So, if you take up more space wouldn’t you have greater pressure?
3. Pressure has nothing to do with molecules pushing on each other, as you said.  Thus, the size of the particles has nothing to do with measuring the pressure.