The Chemistry of Gunpowder

What is Gunpowder?

What is Gunpowder

• Chemical explosive in the form of a powdered mixture
• invented in China and the first chemical explosive available
• was used widely as a propellant in firearms, explosives, technology, and is still used in fireworks
• produces a lot of heat and gas volume once ignited

What is Gunpowder Made Out of?

Three different components:

1. potassium nitrate (75%)

2. charcoal (%15)

3. sulfur (%10)

Components of Gunpowder

Component #1: Potassium Nitrate (KNO3)

Potassium Nitrate

• allows for oxygen in the reaction (oxidizer)

2KNO3 ---> 2KNO2 + O2

• decomposes at a high temperature
• promotes rapid burning of other ingredients

Component #2: Charcoal (C7H4O)

• Charcoal is a source of carbon which is used as fuel
• has a lower auto ignition temperature than pure carbon
• needed for an explosive reaction

Charcoal

Component #3: Sulfur (S)

• included for it's ability to undergo exothermic reactions at low temperature
• lowers the ignition temperature of the charcoal
• increases combustion rate

Sulfur

Chemical Equation of Gunpowder

Balanced and simplified equation of the combustion of gunpowder:

Chemical Reaction

10 KNO3(s) + 3 S(s) + 8 C(s) → 2 K2CO3(s) + 3 K2SO4(s) + 6 CO2(g) + 5N2(g)

More accurate chemical equation of the combustion of gunpowder

(including charcoal (C7H4O)):

6 KNO3(s) + C7H4O(s) + 2 S(s) →K(2)CO3(s) + K2SO4(s) + K2S(s) + 4 CO2(g) + 2 CO(g) + 2 H2O(l) + 3 N2(g)

How Gunpowder Works

Diagram of an Explosion with Gunpowder:

How It Works

10 KNO3(s) + 3 S(s) + 8 C(s) → 2 K2CO3(s) + 3 K2SO4(s) + 6 CO2(g) + 5N2(g)

• carbon dioxide and nitrogen gases compress and than expand due to the high pressure
• positive entropy change

References

Wikipedia contributors. "Gunpowder." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 15 Oct. 2018. Web. 5 Nov. 2018. https://en.wikipedia.org/w/index.php?title=Special:CiteThisPage&page=Gunpowder&id=864206563

Brunning, Andy. “The Chemistry of Gunpowder” Compound Interest, 2 July 2014. Web. 5 Nov. 2018. https://www.compoundchem.com/2014/07/02/the-chemistry-of-gunpowder/

Helmenstine, Anne Marie, Ph.D. "Gunpowder Facts and History." ThoughtCo, 22 July 2018. Web. 5 Nov. 2018. thoughtco.com/gunpowder-facts-and-history-607754.

Reinschmidt, Isaac. “The Chemistry of Gunpowder.” Chemistryislife, n.d. Web. 5 Nov. 2018. http://www.chemistryislife.com/the-chemistry-of-gunpowder

Goodnight, Seth. “Chemistry of Explosives.” Feed the Data Monster, 5 Nov. 2014. Web. 5 Nov 2018. http://feedthedatamonster.com/home/2014/11/5/explosives

Blackwood, J.D. “The initiation, burning and thermal decomposition of gunpowder” The Royal Society, 8 July 1952. Web. 10 Nov 2018. http://rspa.royalsocietypublishing.org/content/213/1114/285

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