#### CHEMICAL FORUM

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Newbie

Joined: 07 Oct 2016
Posts: 3
 Posted: Fri Oct 07, 2016 2:41 am    Post subject: Balancing reactions with multiple oxidation state changes? I have learned to balance equations that have 2 or 3 changes in oxidation states, like: Zn + HNO3 = Zn(NO3)2 + NH4NO3 However I can't do this with equations like the one below that have more than 3 changes: CH4 + O2 = C2H2 + CO + H2 I know it can be balanced easily with other methods but, I want to learn this method completely, so... . Could you explain this CH4 + O2 = C2H2 + CO + H2 using Oxidation states? Thank you all.

Distinguished Member

Joined: 22 Feb 2009
Posts: 1624
 Posted: Thu Oct 13, 2016 8:44 pm    Post subject: Try to split it into two parallel reactions and then combine them back into one CH4 + O2 = C2H2 + CO + H2 __________________________ CH4 + O2 = CO + H2 CH4 = C2H2 + H2 In reality these are two separate processes, and they can occur in different ratios, depends on conditions: temperature, catalyst, etc. For example, on every 10 first reactions only one second reaction occur. For simplicity (for school task) combine them with the lowest numbers. Please try by yourself and give us the answer_________________Remember safety first! Check MSDS and consult with professionals before performing risky experiments.

Newbie

Joined: 07 Oct 2016
Posts: 3
 Posted: Sat Oct 15, 2016 10:08 am    Post subject: Thanks, I got it! I balanced the two reactions and the sum of them balanced the first equation. 4 1 2 1 7 Another question came to my mind; How can I find out the way to divide the equation? Should I know the reactions or is there another way to do it?

Distinguished Member

Joined: 22 Feb 2009
Posts: 1624
 Posted: Sat Oct 15, 2016 10:40 am    Post subject: To identify parallel reactions follow elements that change oxidation state to different levels. For example, in this case CH4 + O2 = C2H2 + CO + H2 C4- ==> C2- (for CO) C4- ==> C- (for C2H2) these are to independent processes of oxidation of the same molecule: methane For example, in this real case vanadium-catalyzed oxidation of ammonia http://www.sciencedirect.com/science/article/pii/S0920586106000496 NH3 + O2 ==> NO + NO2 + H2O Two distinct processes can be identified: NH3 + O2 ==> NO + H2O NH3 + O2 ==> NO2 + H2O You can easily balance each and them mix them in any ratio In general case look for changes of the same element into different compounds and analyze for a possibility of mixed reaction. Here is a simple example NaOH + KOH + HCl ==> NaCl + KCl + H2O in this particular case Cl- plays role in both independent reactions Here is another example (read GrahamKemp's answer) http://chemicalforum.webqc.org/viewtopic.php?t=19314_________________Remember safety first! Check MSDS and consult with professionals before performing risky experiments.

Newbie

Joined: 07 Oct 2016
Posts: 3
 Posted: Sat Oct 15, 2016 12:34 pm    Post subject: That was awesome! Really enjoyed it, thank you a lot expert.

Full Member

Joined: 21 Aug 2017
Posts: 10
Posted: Mon Aug 21, 2017 5:28 am    Post subject:

 expert wrote: To identify parallel reactions follow elements that change oxidation state to different levels. For example, in this case CH4 + O2 = C2H2 + CO + H2 C4- ==> C2- (for CO) C4- ==> C- (for C2H2) these are to independent processes of oxidation of the same molecule: methane For example, in this real case vanadium-catalyzed oxidation of ammonia http://www.sciencedirect.com/science/article/pii/S0920586106000496 NH3 + O2 ==> NO + NO2 + H2O Two distinct processes can be identified: NH3 + O2 ==> NO + H2O NH3 + O2 ==> NO2 + H2O You can easily balance each and them mix them in any ratio In general case look for changes of the same element into different compounds and analyze for a possibility of mixed reaction. Here is a simple example NaOH + KOH + HCl ==> NaCl + KCl + H2O in this particular case Cl- plays role in both independent reactions Here is another example (read GrahamKemp's answer) http://chemicalforum.webqc.org/viewtopic.php?t=19314

The post has good info
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