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anonymous

  • one year ago

solution is made by dissolving 25.5 grams of glucose (C6H12O6) in 398 grams of water. What is the freezing-point depression of the solvent if the freezing point constant is -1.86 °C/m? Show all of the work needed to solve this problem.

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  1. taramgrant0543664
    • one year ago
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    So for this one we have a couple extra steps so first we have to find the number of moles of glucose to do this: n=m/MM moles= mass / molar mass So mass is the 25.5g and the molar mass of glucose is 180.16 So 25.5/180.16=n n=?

  2. anonymous
    • one year ago
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    n=0.142

  3. taramgrant0543664
    • one year ago
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    Great! So next step we need to find moles per kg of water but first we have to convert 398g into kg so you divide by 1000 as that is the conversion

  4. anonymous
    • one year ago
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    0.398

  5. taramgrant0543664
    • one year ago
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    Yes so now we can figure out the moles per kg m=0.142/0.398 m=?

  6. anonymous
    • one year ago
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    0.357

  7. taramgrant0543664
    • one year ago
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    Yes 0.357moles/kg, so the next step is the van't Hoff factor which again is represented by i, it is a dissociation factor, glucose doesn't dissociate in water so i=1 for this example

  8. taramgrant0543664
    • one year ago
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    Second last step now is to find our change in temperature: T=iKfm i is 1, Kf is given so -1.86 and m is the 0.357 we found previously

  9. anonymous
    • one year ago
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    T=(1)(-1.86)(0.357) = -0.664

  10. taramgrant0543664
    • one year ago
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    Yes so that is the change in temperature when the glucose is mixed in so to find the freezing point we add this to the freezing point of water So 0+(-0.664)= -0.664 celcius is the freezing point of this reaction

  11. anonymous
    • one year ago
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    why 0?

  12. taramgrant0543664
    • one year ago
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    Because 0 is the freezing point of water

  13. taramgrant0543664
    • one year ago
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    When we did the boiling point we used 100 as that is the boiling point of water

  14. anonymous
    • one year ago
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    ok so the answer is -0.664?

  15. taramgrant0543664
    • one year ago
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    Yes it would be

  16. anonymous
    • one year ago
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    thx

  17. taramgrant0543664
    • one year ago
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    No problem! Happy to help!!

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