What's the molecular formula of a compound with 52% C, 3.15% H, 44.4% Cl if the formula weight is 320g/mol?

Assuming 100g of the substance, giving 52g C, 3.15g H, and 44.4g Cl. What is the molecular formula?

Thanks.

Update:

If possible, please provide the solution. Thank you!

2 Answers

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  • 1 decade ago
    Favorite Answer

    OK....you've done the first step, by looking at 100g

    Now, the second step is to convert each element to no of moles, by dividing mass by molar mass:

    C: 52 / 12 = 4.33 mol

    H: 3.15 / 1 = 3.15 mol

    Cl: 44.4 / 35.5 = 1.25 mol

    Now, divide all mol by the smallest quantity, which in this case is that of Cl (1.25).

    C: 4.33 / 1.25 = 3.464 approx equal to 3.5

    H: 3.15 / 1.25 = 2.52 approx equal to 2.5

    Cl: 1.25 / 1.25 = 1

    However, we cannot have fractions in the formula, so multiply everything by 2:

    C: 3.5*2 = 7

    H: 2.5*2 = 5

    Cl: 1*2 = 2

    So the empirical formula is C7H5Cl2

    The molar mass of the empirical formula is 160

    But the formula mass is 320

    So the number of units of the empirical formula in the molecular formula is (320/160) = 2

    So your molecular formula is (C7H5Cl2)2 = C14H10Cl4

    I hope it's right.

  • 1 decade ago

    First, you need to find molar ratio.

    C: 320(.52/12) = 14 mol

    H: 320(.0315/1) = 10 mol

    Cl: 320(.444/35.45) = 4 mol

    Therefore, the molecular formula is C14H10Cl4

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