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General chemistery questions

Discussion in 'Pre-Dental' started by ibo man, Aug 13, 2002.

  1. ibo man

    ibo man Senior Member 10+ Year Member

    175
    0
    Nov 1, 2001
    Could someone please help me out on this one. I tried doing it but the I got D as the answer, while the right answer is E.

    A) 5.8g of sodium chloride is added to 500g of water. The freezing point of the solution is approximately.
    A. -1.9*C
    B. -9*C
    C. -3.8*C
    D. -0.19*C
    E. -0.75*C

    B) An aqueous solution containing 0.5 moles of glucose has a boiling point of 100.3*C. What would be the approximate boiling point if 0.5 moles NaCl were used instead of 0.5 moles of glucose?

    A. 100*C
    B. 100.15*C
    C. 100.3*C
    D. 100.6*C
    E. 100.9*C
    for question B correct answer is D. Thanks
     
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  3. DATMATT

    DATMATT SISU 7+ Year Member

    155
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    Jan 12, 2002
    question B tests on colligative properties. NaCl breaks into two ions, sugar is one so it essentially doubles the .3 degree increase. However the difference in the molar mass of glucose and NaCl might make you wonder, however, the gave molar amounts and not gram amounts so you actually have quite a difference in the mass of the two compounds.
     
  4. DATMATT

    DATMATT SISU 7+ Year Member

    155
    0
    Jan 12, 2002
    In question A I am not sure how they get that answer? The equation that I would think to use is deltaT = Kmx. The molality of the soln is about .1 and the x value is 2 since NaCl breaks into two ions BUT WHERE IS K? HELP!
     

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