P Perkerson A little reminder You have learned previously that during combustion reactions some type of fuel is burned and water and carbon dioxide are the products Sometimes the fuel is a hydrocarbon contains only carbon and hydrogen and sometimes there are other components to the fuel ID: 242793
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Slide1
Combustion Analysis
P. PerkersonSlide2
A little reminder!
You have learned previously that during combustion reactions some type of fuel is burned and water and carbon dioxide are the products. Sometimes the fuel is a hydrocarbon (contains only carbon and hydrogen) and sometimes there are other components to the fuel.
Ex. Methane combusts in the presence of oxygen
CH
4
+
2O
2
CO
2
+ 2H
2
O
Methanol combusts in the presence of oxygen
2CH
3
OH
+
3O
2
2CO
2
+
4H
2
OSlide3
Finding the empirical formula of a fuel
If given the components of the fuel, mass of original substance, mass of products (water and carbon dioxide) we can determine the empirical formula. If given the molecular mass of the original substance, we can also determine the molecular formula. However, this only works if combustion is complete – meaning that all of the fuel is consumed in the reaction.Slide4
Let’s do an example!
Combustion of 0.255 grams of isopropyl (a fuel composed of C,H, & O) produces 0.561 g CO
2
, 0.306 g H
2
O
Step 1: Find the grams of carbon
Step 2: Find the grams of hydrogen
Subtract the mass of the carbon & hydrogen from the original mass. That gives you the mass of the oxygenSlide5
Now that you have the masses for all three components, you can convert grams to moles, divide all by the small, etc.Slide6
Let’s try another!
What makes dirty socks so stinky?
Caproic
acid – composed of carbon, hydrogen and oxygen. A 0.225 g sample has 0.512 g CO
2
and 0.209 g H
2
O
Find the mass of the carbon.
Find the mass of the hydrogen.
Find the mass of the oxygen.Slide7
Mass to moles: divide all by small to get the empirical formulaSlide8
If the molecular mass of “stinky socks” is 116.01 grams per mole, what is the molecular formula?Slide9
You try this one on your own!
A 0.548 g sample of a fuel composed of carbon, hydrogen and nitrogen is completely combusted. 0.312 grams of water and 1.525 grams of carbon dioxide are produced. The molecular formula mass is 79.01 grams per mole. What are the empirical and
molecular formulas?