The Empirical Formula of an Organic Compound

What is ORGANIC COMPOUND?

Does that mean that the compound is twice as expensive and has absolutely no difference whatsoever? (distastefully biased plug on organic foods) No, it means that the compound contains carbon. BUT it is noteworthy that certain compounds containing carbon are indeed inorganic, like carbides and carbonates. In this lesson we learn how to calculate the empirical formula of such compounds with chemistry's favorite furry little critter, MOLES.

The smell of vinegar is caused by acetic acid (CH3COOH). It is an organic compound

We know that the empirical formula will contain the elements C and H because they are common in all organic compounds. What we do not know, are the amounts of each. If we let x represent the number of carbon and y represent the number of hydrogen, we can use a method to solve for each. THERE ARE 5 STEPS THAT ONE MUST TAKE TO ACHIEVE THIS GLORY. Actually 6, but the 6th is situaltional. It is also noteworthy that when an organic compound combusts, the compounds carbon dioxide and water are ALWAYS formed.

1st STEP:

Convert the mass of the CO2 and H2O 

2nd STEP:

Find the moles of C and H from the moles of CO2 and H2O

There is 1 carbon in CO2 and 2 hydrogens and H2O so basically multiply the value of H2O in moles obtained from the previous step by 2

3rd STEP:

Divide both your values by the smallest molar amount

4th STEP:

Change the ratios until a whole number for both is reached by multiplying by 1 (2/2, 3/3, 4/4) ETC

The empirical formula will be represented by the fraction obtained

5th STEP:

Convert moles back to grams and add them to Check your work

Confused? EXAMPLES HO!

A 3.79 g sample of an organic compound is burned to yield 6.61 g of CO2 and 3.59 g of H2O. Find the empirical formula.

STEP 1:

(6.61g CO2)(1 mol CO2/44.0g CO2) = 0.150 mol CO2

(3.59g H2O)(1 mol H2O/18.02g H2O) = 0.199 mol H2O

STEP 2:

(0.150 mol CO2)(1 mol C/1 mol CO2) = 0.150 mol C

(0.199 mol H2O)(2 mol H/1 mol H2O) = 0.398 mol H

STEP 3:

0.150 mol C/0.150 mol C = 1

0.398 mol H/0.150 mol C = 2.65

STEP 4:

(2.65/1)(3/3) = 8/3 ----> 8 = y 3=x

C3H8

STEP 5:

(0.150 mol C)(12 g/1 mol)= 1.80g C

(0.398 mol H)(1 g/1 mol) = 0.398g H

1.80 + 0.398 = 2.198

BUT WAIT! 2.198 != 3.97.

EXPLAINED: Some organic compounds may contain oxygen aswell. THUS, the sample mass - mass of C and H = mass of oxygen

Dude, most likely jewish, teaching this: