Combustion Analysis

Combustion analysis is a technique where an organic compound is combusted (exploded!!!) and the products are quantitatively measured. 

Understanding Combustion Analysis

Concept: Combustion Analysis Determination 

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Video Transcript

Now before we tackle this combustion analysis question, it's important for us to identify what exactly is a typical combustion reaction. We're going to say under a combustion reaction, a compound made up of carbon and hydrogen or carbon, hydrogen, and oxygen will react with oxygen gas. Remember, oxygen is a diatomic molecule so it's O2. The product's form would be water and carbon dioxide. So this is your typical combustion reaction.
Now good examples of this we could have CH4 reacting with O2 and we know that the products are going to be water and CO2. All we're going to do here is balance it and there goes our first example of a combustion reaction.
Now CH4 only has carbon and hydrogens. Let's look at one that has carbon, hydrogen, and oxygen that reacts with O2. A good example of this would be glucose, a simple sugar that we use for energy every day. Glucose reacts with atmospheric oxygen, O2, and it too will form water and carbon dioxide, and we balance it.
So these are our two examples of combustion. 

In a combustion reaction an organic compound made of carbon and hydrogen or carbon, hydrogen and oxygen is combusted to form carbon dioxide and water as products. 

Example: A 0.2500 g sample contains carbon, hydrogen and oxygen and undergoes complete combustion to produce 0.3664 g of CO2 and 0.1500 g of H2O. What is the empirical formula of the compound?

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Combustion Analysis Additional Practice Problems

In the combustion of hydrogen gas, hydrogen reacts with oxygen from the air to form water vapor. If you burn 33.5 g of hydrogen and produce 299 g of water, how much oxygen reacted?


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The combustion of ethane (C2H6) produces carbon dioxide and steam:

2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l)

How many moles of CO2 are produced when 5.85 mol of ethane are burned in an excess of oxygen?

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On combustion analysis, a 0.450 g sample of a chemical compound gives 0.418 g of water and 1.023 g of carbon dioxide. Assuming that the empirical formula of the compound is CxHyOz, find the values of x, y and z.

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A strip of pure copper metal weighing 3.178 g is heated in the presence of oxygen gas. In the process, all of the copper reacts with oxygen to form 3.978 g of a black copper oxide. What is the empirical formula for this copper oxide?

Given that the molar mass of the compound is about 80 g, name this compound.

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Determine the empirical formula for a hydrocarbon if the complete combustion of a sample produces 5.28 g of CO2 and 1.62 g of H2O.

 

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If 3.25 g of butane (C4H10, M = 58.14) is burned (combusted) in the presence of excess O2, what is the mass of CO2 that forms, in g?

Enter your answer with 2 decimal places and no units.

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The heat of combustion of butane (C4H10) is −2878 kJ/mol. Assume a typical cigarette lighter holds about 1.75 g of butane. How much heat energy would be released if ALL of the butane in the lighter were combusted?

1. 86.63 kJ 

2. 95.59 kJ

3. 40.61 kJ

4. 1.05 kJ

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The combustion of 4.16 grams of a compound which contains only C,H,O and F yields 7.7 g CO2 and 2.52 g H2O. Another sample of the compound with a mass of 3.63 g is found to contain 0.58 g F. What is the empirical formula of the compound? 

A. C3H8O2F

B. C4H10OF

C. C4H8OF

D. C5H8O2F

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Combustion analysis of a 12.01 g sample of tartaric acid, which contains only  carbon, hydrogen, and oxygen, produced 14.08 g CO2 and 4.32 g H2O.

a) What is the empirical formula of tartaric acid?

 

 



 

 

 

 

b) If 0.250 moles of the compound weighs 37.52 g, what is the molecular formula of the compound?

 

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2.404 g of a compound were burned in oxygen and found to produce only 3.520 g CO(g), 2.564 g SO2 (g) and 1.440 g H2O (l). Determine the empirical formula of the compound.

A) C2SH4

B) C2SH2

C) CSH

D) C4SH

E) C2S2H4

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Isoeugenol is the compound which gives the characteristic odor to nutmeg and contains carbon, hydrogen, and oxygen. If a 0.500 g sample of isoeugenol is combusted it gives 1.341 g of CO2 and 0.329 g of H2O. Isoeugenol has a molecular weight of 164 g/mol. What is the molecular formula of isoeugenol?

A) C8H4O4

B) C10H12O

C) C2HO

D) C5H6O

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Combustion analysis of 2.400 g of an unknown compound containing carbon, hydrogen, and oxygen produced 4.171 g of CO2 and 2.268 g of H2O. What is the empirical formula of the compound?

A) C2H5O2

B) C2H5O

C) C2H10O

D) C3H8O2

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Combustion analysis of an unknown compound containing only carbon and hydrogen produced 4.554 g of CO2 and 2.322 g of H2O. What is the empirical formula of the compound?

A) C4H10

B) CH

C) C2H5

D) C5H2

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