Emperical && Molecular Formulas?
Cyclopropane, a gas used with oxygen as a general anesthetic, is composed of 85.7 percent C and 14.3 percent H by mass. If 1.56 grams of cyclopropane has a volume of 1.00 L at 0.984 atm and 50.0oC, what are the empirical and molecular formulas of cyclopropane?
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find moles, kusing molar mass:
85.7 g carbon @ 12.0 g/mol = 7.14 moles C
14.3 g Hydrogen @ 1.00 g/mol = 14.3 mol H
divide by the smaller moles
7.14 moles C / 7.14 = 1 mole carbon
14.3 g / 7.14 = 2 mol H
your empirical formula is CH2
(which has a formula mass of 14g/mol)
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find moles;
PV = nRT
(0.984 atm)(1.00L) = n(0.0821 L-atm/mol-K)(323K)
n = 0.0371 moles of cyclopropane
find molar mass of cycloproptane:
1.56 g / 0.0371 mol =
42 g/mol
that's 3 times as massive as the empirical formula mass
yoiur molecular formula is C3H6