Examkrackers chemistry questions

Discussion in 'MCAT Study Question Q&A' started by masterMood, Jun 19, 2008.

  1. masterMood

    masterMood Banned
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    Number 67 page 63 of the examkrackers general chemistry book.

    The answer is D, which I understand but why is A. Heat can be changed completely to work in cyclical processes true?


    I thought that heat could never be 100% turned into work???

    Also did anyone find the description of thermodynamics (chapter 3) to be pretty ****ty? I used my own intuition to figure out most of the questions in this chapter. I felt like they were going into detailed theory a lot more than it should've been done (maybe i'm wrong???). I feel like this was mathematics except analyzing why we add or subtract and how it was derived and all this unnecessary stuff. Or do we need the abstract knowledge of thermodynamics..
     
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  3. engineeredout

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    FOr future reference, you probably wanna write out the actual question because not everyone has the EK books. I just happened to go through this section today actually.

    "Which of the following is a violation of the law of conservation of energy?"

    A: Heat can be changed completely to work in a cyclical process.

    D: A bond is broken and energy is released.

    You're right that heat cannot be converted 100% into work (2nd law). That isn't what the question is asking however. Its asking if the statement in principal would violate the law of conservation of energy, which in this case it doesn't. If heat were completely changed to work, then the energy is conserved.

    D is blatently wrong because it is the opposite of what actually happens.


    As for the ****ty thermo chapter, take it from someone who took two semesters worth of chemical engineering thermodynamics. There isn't much more you can get into without starting to use some ****ing complicated math. Almost impossible to go beyond that point without requiring integrals, which is beyond the scope of the mcat.

    Lecture 5 however does go into more thermodynamics: "heat capacity, phase change, and colligative properties". Understanding phase change and phase diagrams are definitely a big part of thermodynamics.
     
  4. masterMood

    masterMood Banned
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    ahhh so my confusion was over semantics instead of the actual logic ha ha.

    Thanks for the help man appreciate it once again!
     
  5. engineeredout

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    Welcome to mcat land.



    Man speaking of chem. Problem 312 in the 1001 g-chem book.
    "Which of the following properties of a person are state functions?

    I. Height
    II. Age
    III. Cholesterol level"


    What a stupid ****ing question.
     
  6. unsung

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    HA. I know. EK has some crazy ****. Once I read the answer I was like okay... that sorta made sense. But still. Age is a "path function" because you have to know a person's "history" in getting to that age? uh.... okay.
     
  7. engineeredout

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    See I thought to answer the question you had to think "For which one of these does the path not taken matter"

    Doesn't matter what you do until you're 60, you're just 60. Doesn't matter when you grew, you just grew. Cholesterol on the other hand, might matter if you got it from eating cheeseburgers or if it was genetic.
     
  8. masterMood

    masterMood Banned
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    wait so what's the answer?

    Wouldn't the answer be all 3?

    It doesn't matter how you got to the age of 60, you are 60.
    It doesn't matter how you got to 5 feet, you are feet.
    It doesn't matter how you got 250 mg of cholesterol in your blood, you have 250 mg of cholesterol. Cholesterol is cholesterol and how you got it doesn't matter as the fact you have that much (irregardless of source).

    So it the answer all 3?
     
  9. engineeredout

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    The actual answer was I and III only.

    "State functions are quantities that, at least in theory, can be measured without knowing anything about the history of the system. Height can be measured with a scale. Cholesterol level can be measured by a blood test. Age cannot be measured in this way; you have to know when the person was born. Admittedly you might be able to guess a person's age by the number of gray hairs, wrinkles around the eyes, or some other measure, but we all know these traits are affected by other factors besides age (sun exposure, for example)."

    Stupid ****ing question.
     
  10. masterMood

    masterMood Banned
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    yo did you think that the 30 minute lecture exam for LECTURE 3 was insanely difficult?
     
  11. 161927

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    Funny question. I would have only picked "Age" as a state function because nothing you do changes the rate at which you age, assuming time progresses linearly. Height and cholesterol could be affected by life choices, by the path one takes.
     

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