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AP Chemistry

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How many grams of sucrose (C12H22O11)
must be dissolved in 60 g water to make a
solution in which the mole fraction of sucrose is 0.4?
Answer in units of g.

  • AP Chemistry - ,

    60 g H2O = ? mols. mol = grams/molar mass.
    mols sucrose = grams/molar mass.

    Xsucrose = mols sucrose/total mols.
    You know Xsucrose. Substitute that into X formula and solve for g sucrose. Post your work if you get stuck.

  • AP Chemistry - ,

    I don't really understand how to set it up. I'm to figure out my moles for water but after that I'm stuck.

  • AP Chemistry - ,

    mols H2O = 60g/18 = 3.33
    mols sucrose = n
    total mol = 3.33 + n

    Xsucrose = mols sucrose/(total mols)
    0.4 = [n/(n+3.33)]
    Solve for n = mols sucrose.

    Then mols sucrose = grams sucrose/molar mass sucrose.
    You know mols sucrose from the above calculation. You know molar mass sucrose (about 342), solve for grams and you have it.

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