Science Buddies: "Ask an Expert"

I am making Potassium Nitrate and sugar rocket and and I need a mathematical equation that proves the chemical formula works, how do I do It?

Thanks

If you mean the chemical formula, you can find that pretty easily on the internet. I found two discussions you might like to look at:

http://www.scienceforums.net/topic/2316 ... ket-fuels/

http://www.scienceforums.net/topic/1936 ... moke-bomb/

The first of these two suggests 12KNO3 + C6H12O6 = 6 CO2 + 6 H2O + 12 KNO2 is the ideal reaction which may or may not happen in your homemade rocket. The other thing these discussions all point out is how incredibly dangerous it is to make this stuff. Stories abound with people blowing up microwaves, or exploding rock tumblers. PLEASE ask an adult how to make and test your compound carefully. Just because it's made with kitchen chemicals doesn't mean it's safe.

I'm not a chemist but I was a kid and a rocket fan. I know how fun this stuff is, and have enough close calls to know how dangerous. Be smart and safe.

Hello,
Thanks for the advice but I have the chemical formula but isn't there a mathematical equation that proves the chemical formula works? There has to be a mathematical reason for why they react otherwise they would just sit there.

I am aware of the danger with this experiment and will be taking extreme care when assembling and conducting this experiment.

Thankyou.

I just wanted to thank you for acknowledging the potential danger, wish you good luck with your project and to say that in the high school chemistry and the one course I took in college, I'm not familiar with 'mathematical' chemical equations. Perhaps one of the expert chemists here can weigh in. Or if you post an example from some other reaction - maybe us non-chemists know these equations by another name?

I'm sorry I can't help you further.

Howard

Okay thank you for you help, I'll try that then.

Thanks, bye!

Hi Seb_grubb1380,

You are looking for a "mathematical" reason as to why the reaction happens, correct? A branch of science called thermodynamics can help you with this. Have you taken a chemistry class yet?

Chemical reactions "happen" when two conditions are met. First, the energy of the products of the reaction must be lower than the energy of the reactants. Second, the energy barrier associated with the reaction must be overcome. This second factor can be incredibly important. For example, at ambient conditions, graphite, not diamond, is the lowest energy form of carbon. According to the first factor, all of the diamonds in people's jewelry should convert to graphite because graphite has the lower energy under the conditions we have on Earth's surface. But, the diamond rings people wear don't spontaneously turn into graphite (pencil lead). This is because the activation energy barrier associated with the reaction C(diamond) -> C(graphite) is quite large.

Thermodynamics allows you to calculate several quantities that can be used to determine whether a reaction is likely to happen. At a given temperature and pressure, a quantity called the "Gibbs free energy of reaction" tells you whether a reaction will happen spontaneously (as long as there aren't any significant activation energy barriers). The following website discusses the Gibbs energy in more detail, but at a level appropriate for high school. Check it out, and post back if you have questions about it.

http://education-portal.com/academy/les ... cance.html

I calculated the Gibbs energy of reaction for the reaction HowardE gave you. It comes to -1840 kJ/mole. This value is less than zero, so the reaction is spontaneous. The decrease in free energy associated with the reaction (-1840 kJ/mole) is why the chemical formula "works".

Post back if you have more questions. This post is a very brief brush with a much richer topic, so if you want to know more details, please let me know. But, if all you wanted was a mathematical reason why the reaction happens, hopefully this post answered your question.

Hello,

Thank you very much It has taken me a long time to finally get where I am now. I will study the information you have given me and if I have any more questions I'll be sure to get back to you.

Thanks,
Sebastian