Butane Combustion Analysis Demo for a High School Chemistry Class

In summary, the high school chemistry teacher is looking to develop a lab experience for demonstrating combustion analysis using a simple butane torch or bic lighter. They plan to set up glassware to collect the vapors of the flame and use absorbers to collect CO2 and H2O. The teacher is interested in the practical considerations and quantities of the absorbers needed. The goal is to show how combustion analysis can lead to an empirical formula for the hydrocarbon being burned. They are considering using a candle instead of butane.
  • #1
mishima
558
34
Hi, I'm a high school chemistry teacher trying to develop a lab experience demonstrating combustion analysis. This is usually something we go through theoretically during discussion of percent composition and empirical formula. I'd like to actually perform one.

I was wondering if this could be done with a simple butane torch, or even a simple bic lighter?

I would setup the glassware to collect the vapors of the flame as follow:

--Open flame leading to long flute
--Flute going into 2-hole rubber bung in 150 mL erlynmeyer flask partially filled with calcium chloride (water absorber)
--Intake goes all the way to the bottom, submerged in the absorber
--Outlet runs to 2-hole rubber bung in second 150 mL erlynmeyer partially filled with sodium hydroxide (CO2 absorber)
--Again intake goes all the way to the bottom, submerged
--Outlet goes to vacuum

I've only ever seen this in textbook pictures and so am not really aware of any practical considerations here, especially the quantities of the absorbers required.
 
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  • #2
mishima said:
--Open flame leading to long flute
"Flute," or flue? You've not begun or ended the combustion, so you're looking for qualitative demonstration of formation of CO2 and H2O?
 
  • #3
Not sure of the correct term, but its basically an inverted glass funnel.

I am certainly not looking for a qualitative demonstration of the formation of those products, we have already studied combustion itself on the qualitative level. The point is to see how combustion analysis can lead to an empirical formula for the hydrocarbon being burned. Masses of CO2 and H2O are converted into mol C and mol H. A pseudoformula with fractional subscripts is then turned into an empirical formula with whole integer subscripts. Despite butane having a formula easily stated using organic nomenclature rules, I think there is value in demonstrating the procedure.
 
  • #4
You're looking for CnH(2n + 2) in a poorly defined mixture,
mishima said:
simple butane torch
, which is properly LP, a mixture of C(1-5) saturated and unsaturated hydrocarbons. i.e., you are not going to get "whole integer subscripts." You might want to look at/google "fuel gas combustion calorimetry."
 
  • #5
No reason it has to be butane, just looking for something on hand. How about just burning a candle?
 
  • #6
mishima said:
a candle?
Same thing, a mixture.
 

1. What is the purpose of the Butane Combustion Analysis Demo?

The purpose of this demo is to illustrate the process of combustion and the chemical reaction that occurs when butane is burned in the presence of oxygen. This can help students understand the concepts of oxidation and combustion, as well as the role of catalysts in chemical reactions.

2. What materials are needed for the demo?

To perform this demo, you will need a Bunsen burner, a butane canister, a ceramic tile or heat-resistant surface, a beaker or flask, a wooden splint, and a source of ignition such as a match or lighter. Safety goggles and a fire extinguisher are also recommended.

3. How do you perform the Butane Combustion Analysis Demo?

First, place the ceramic tile or heat-resistant surface on a table. Next, connect the Bunsen burner to a gas source and adjust the flame to a blue, pointed flame. Then, place the beaker or flask over the flame and insert the wooden splint into the flame. Slowly release the butane gas from the canister over the flame and observe the reaction. Finally, extinguish the flame and allow the beaker or flask to cool before handling it.

4. What observations can be made during the demo?

During the demo, students can observe the color and intensity of the flame, the formation of soot on the ceramic tile or heat-resistant surface, and the production of carbon dioxide and water vapor as byproducts. They may also notice the heat given off by the reaction and the decrease in the volume of the butane gas as it is consumed.

5. What are the key takeaways from the Butane Combustion Analysis Demo?

The key takeaways from this demo are the concepts of combustion and oxidation, the role of oxygen as a reactant, and the formation of carbon dioxide and water as products. Additionally, students can understand the importance of safety precautions when working with flammable materials and the use of proper lab techniques when conducting experiments.

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