March 29, 2017

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A 0.02882 g sample of gas occupies 10.0-mL at 288.5 K and 1.10 atm. Upon further analysis, the compound is found to be 38.734% C and 61.266% F.

What is the molecular formula of the compound?

What is the geometry shape around each carbon atom?

Polar or Nonpolar?

  • Chemistry - ,

    Use PV = nRT and solve for n = numbre of mols. Substitute into n = grams/molar mass. You know mols and grams, solve fo rmolar mass. Use that number later.

    Take a 100 g sample which gives you
    38.734 g C and 61.266 g F. Convert to mols.
    38.734/12 = ?
    61.266/19 = ?

    Find the ratio of C to F with the smallest number being 1.00. The easy way to do that is to divide the smaller number by itself; then divide the other number by the same small number. That gives you the empirical formula.

    Calculate the mass of the empirical formula and substitute into
    empirical formula x ?number = molar mass from above and round ?number to a whole number.
    The molecular formula is (CxHy)?
    Post your work if you get stuck.

  • Chemistry - ,

    For n I got 26.18 mols. For the mass I got 31 because it was CF.

  • Chemistry - ,

    26.18 is not right. CF is the empirical formula. The empirical mass is not 31. You need the molar mass from mols and grams.

  • Chemistry - ,

    The moles of C is 3.227. The moles of F is 3.224. Therefore the empirical formula is CF. How would I find the empirical mass? Your explanation is confusing.

  • Chemistry - ,

    Yes, I said the empirical formula of CF is correct. My error for empirical mass; it is 12 + 19 = 31 as you noted.
    Here is how you do the molar mass.
    PV = nRT
    P = 1.10 atm
    V = 10.0 mL = 0.0100 L
    n = solve for this
    R = 0.08206 L*atm/mol*K
    T = 288.5 K.
    Solve for n = about 5E-4 but that is just a close estimate.
    Then n = grams/molar mass and
    about 5E-4 = 0.02882/molar mass.
    Solve for molar mass which is approximately 60.
    The molecular formula then is
    empirical formula x ? number = molar mass
    31 x ? = 60
    ? = about 2 when rounded to a whole number; theefore, the molecular formula is
    (empirical formula)2 or
    You should go through and confirm those numbers since they are just estimates on my part.

  • Chemistry - ,


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