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[bio/chm] Questions

Discussion in 'DAT Discussions' started by ippie, Jun 5, 2008.

  1. ippie

    ippie ippie

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    #1.
    drosophila melanogaster can have several eye colors. red eyes are dominant over white eyes and sepia eyes. If a red eyed fly that resulted from a mating of red eyed and sepia eyed parents is crossed with a sepia eyed fly, what percentage of the offspring will have sepia eyes?

    ==> Accroding to answer, genotype of sepia eyes is homozygous recessive, rr. then what is the genotype of white eyes? I thought white eye is rr, and sepia eye is Rr.


    #2.
    H=131KJ/mol
    S= 134J/mol K
    C(s) + H2O (l) --> CO (g) + H2 (g)
    at what temperature wil the reaction become spontaneous?
    a. 1250 C
    b. 1022 C
    c. 978 C
    d. 900 C
    e. 749 C

    ==> Be careful. the answer choice is giving you a unit of celcius, not K. I think the answer could be ALL, but the answer is E. why?


    #3.
    when 100g fo an unknown compound is dissolved in water to porduce 1L of solution, the pH of the resulting solution is measured as 4.56. which of the following statements is most likely true of the unknown compound?
    a. it is a weak acid with a pKa of more than 1.
    b. it si a weeak acid with a formula weight of less than 10g/mol

    ==> answer is A. I don't understand A.


    #4.
    increasing the amount of liquid in a sealed container wil cause the vapor pressure of the liquid to
    a. increase, if the liquid is sufficiently volatile.
    b. remain the same, regardless of the identity of the liquid.
     
    #1 ippie, Jun 5, 2008
    Last edited: Jun 5, 2008
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  3. Mstoothlady2012

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    #1 you can choose red eye as RR, white eye as ww/rr, sepia eye as ss/rr. Rr is heterozygous and since red eye is dominant, Rr would be red eye not sepia

    #2 I am getting all of the above as well.
     
  4. smile101

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    I don't know what exactly you are asking in the first question, I would think that sepia eyes are 50%.

    2) I would pick E b/c 749 + 273 is 1020K, which is the minimum you need to have spontaneous rxn. Your entropy is in J instead of KJ, so you have 131-T.134, which means you need atleast 1000 K temp to have a spontaneous rxn.

    3) B is def not right because less than 10 means strong acid. If the pH is 4.5, then pKa can't be too low. Also, pKa is the pH at which 50% of acid is dissociated; if its a strong acid, you know it will dissociate around pH 2 and won't wait till the pH is above 4 (thats the characteristic of a weak acid). If I am not given much numbers to work with, I would work around the answer choices.
     
    #3 smile101, Jun 5, 2008
    Last edited: Jun 5, 2008
  5. Christmasskunk

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    For number 1 the question is not even asking anything about white eyes. So you dont even need to find out what genotype is white eyes... Think they are trying to throw u off course... Kinda tricky..
     
  6. smile101

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    Answer to #4 is b because vapor pressure is only dependent on temperature, not on the amount of liquid.
     
  7. DDSguyLA

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    2. It is E. It's asking at what minimum temp it will be come spon. All the others are correct as well, but starting from 749 the Delta G becomes Negative.

    4. It's B. In a sealed container ONLY temp can change the vp.
     

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