NOVEMBER 13 2009

EMPIRACAL FORMULAS

Find the total mass of Carbon in a 3.0kg sample of ethanol.
(C2H5OH)
^ ^ ^ ^
2(12) 5(1) 1(16) 1(1)=46.0g/mol

C2H6O<--Empiracal Formula Empiracal Formulas are simplest formulas Molecular Empiracal
P4H10 ------> P2H5
C1oH22 ------> C5H11
C6H18O3 ------> C2H6O
N2O4 ------> NO2
(*Think lowest common denomenator*)

Empiracal Formulas the simplest whole number ratios in a compound
Molecular formulas show the actual atoms/ and ...(guys finish the sentence.. i can't read my writing)

FINDING EMPIRACAL FORMULAS:
A sample of an unknown compound is analyzed and found to contain 8.4g of 'C', 21g of 'H', and 5.1g of 'O'
Find the empiracal formula


Example: 0.888 grams of a compound made up of C2H7O
C, H, and O are found to contain 0.576g of C and 0.120g of H
a) Find the mass of oxygen
b) Find the empiracal formula

0.120g

+ 0.57g

-----------

.696

*.696

-.888

----------

.192-->oxygen

C=.192 x mol=0.48-->4

H=.120xmol=.12--->10

O= .192xmol=.012-->1

Homework: Worksheet questions # 22, 23, 24