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chemistry

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How many grams of sucrose (C12H22O11)
must be dissolved in 200 g water to make
a solution in which the mole fraction of su-
crose is 0.1?
Answer in units of g

  • chemistry -

    200 g H2O is how many mols? That's g/molar mass.
    total mol = n sucrose + n H2O
    n sucrose = grams/molar mass sucrose

    [n sucrose/(n sucroswe + nH2O)] = 0.1
    Substitute grams/molar mass for n sucrose and solve for grams.

  • chemistry -

    i got 11.098 for the moles for the first part. so do i add .1 to that?

  • chemistry -

    No. Also if I divide 200/18.015 = 11.102 which is more s.f. than allowed but I carry them and drop at the end of the problem. You can't add them. 11.1 is mols H2O. The 0.1 is not mols sucrose; that 0.1 is the mole fraction of sucrose.
    You must solve this.
    [(x/342)/(x/342)+(11.1)] = 0.1 and solve for x = grams sucrose (Note: x/342 = mols sucrose)

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