Sciencemadness Discussion Board

Stoichiometric Fuel Air Explosions and decibles

gonif86 - 7-3-2021 at 21:36

High school chem class teacher showed 2 parts hydrogen and 1 part oxygen with a nice bang .

What confuses me is what ratio gas to air forms a stoichiometric balanced equation.

Propane

C3H8(g)+5O2(g)→3CO2(g)+4H2O(g)

What about

C3H8(g)+Air →3CO2(g)+4H2O(g)

Can I use a formula to get predicted explosion decibels. I am making a carbide cannon like device

Thank you

njl - 8-3-2021 at 07:09

Probably no. Accurately predicting something like sound intensity would require several variables to be controlled. You would need to know and control fuel composition, air composition, fuel/air ratio, compression ratio, container volume, pressure, material and mass etc... not trivial. If you're ok with a rough approximation that doesn't really mean much you can approximate from the energy released during the reaction.

Maurice-VD-3 - 8-3-2021 at 13:01

If 1 mole propane needs 5 moles O2 to be completely oxidized, one liter propane reacts with 5 liters oxygen O2. And this combustion is made in air, it needs 5 times more air, as air contains only 20% oxygen. So one liter propane requires 25 liters air to be completely oxidized. You may write the equation in air :

C3H8 + 5 O2 + 20 N2 -> 3 CO2 + 4 H2O + 20 N2

gonif86 - 12-3-2021 at 03:41

Thank you for the help.

My experiment worked

Applying chemistry principles I built a safe sound cannon that works great with Calcium Carbide, propane and other gases .

Kids love it. No need for firecrackers that are illegal where I live or homemade M80's