Friday, December 3, 2010

Decemeber 3, 2010

Today we learned how to :

Calculate the Empirical Formula! (organic compounds)

REMINDER! QUIZ on Empirical Formula, Percentage Composition

-Empirical Formulas including organic compound
-burning the compound (react it with O2)
-collecting and weighing of the products resulting from the burning of the compound
-from the mass of the products, the moles of each element in the original organic compound can be calculated

Eg. What is the EF of a compound when 5.0g sample is burned producing 15.0g of CO2 and 8.18g of H20.

Mol CO2 = 15g x (1mol/44.0g) = 0.341 moles

Mol H2O = 8.18g x (1 mol/18.02g) = 0.454 moles

Mol C = 0.431 moles because there is only 1 C in ( CO2) = 0.341 moles | 1.0 | 3
| |
Mol H = O.454 moles x 2 because there is 2 H in (H2O) = 0.908 moles | 2.6 | 8

EF = C3H8

0.341 moles of C x ( 12.0g/1 mol ) = 4.092g of C
0.908 moles of H x ( 1.0g/ 1 mol ) = 0.908g of H

Total Mass = (C) + (H) should equal to 5

so if the final answer equals the amount given in the question, you can reassure that there are not O in the EF.

Another Perfect example and step by step procedures!



A good video explaining how to calculate the Empirical Formula


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