estrone is a female sex hormone that is known to contain 80.0% carbon, 8.2%...

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Sherry D

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...hydrogen, and the remainder oxygen? If 793 mL of estrone is found to have a mass of 4.97 g at 0.90 atm and 200 C, find the molecule formula for estrone?
 
Assume the percents are out of 100.
1) Convert to moles.
80 g C / 12.01 g = 6.66 mol
8.2 g H / 1.01 g H = 8.12 mol
(100 - 80 - 8.2)g / 16.00 g O =.7375

2) Divide by the smallest number (.7375)
C: 6.66 / .7375 = 9
H: 8.12 / .7375 =11
O: .7375/ .7375 =1
--> Empirical formula: C9H11O (Molar mass= 135.2 g)

3) Now to find molecular formula... use PV=nRT where P =.9 atm, V=.793 L, R= 0.0821 atm*L / mol*K, T= 473K and solve for n.
n= 0.183 mol.

4) Using the moles you got from the ideal gas law and from the mass provided for you in the problem (4.97g), find molar mass which is grams/ moles. (4.97 g / 0.183 mol) = 271.

5) Okay, so the molar mass of estrone is 271 and the empirical weight is 135. Divide 271 by 135 to get 2. Multiply the empirical formula subscripts by this number.
--> Molecular formula (C9H11O)2 = C18H22O2.
 
molar mass = mass/n= (RT(4.97g))/PV = (R(473K)4.97)/(793mL(0.9atm)) = 270.3g/mol

270.3*0.8 = 216 = Carbon by weight divide by 12 to find the number of C = 18

H = 270.3*.082 = 22

O = 270.3*.118/16 =2
 
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