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Can you help me balance this chemical equation? N3+H2 --> NH3thanks!

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brandih | eNotes Employee

Posted February 1, 2012 at 1:50 AM via web

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Can you help me balance this chemical equation? N3+H2 --> NH3


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txmedteach | High School Teacher | (Level 3) Associate Educator

Posted February 1, 2012 at 2:07 AM (Answer #1)

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To balance chemical equations, you need to see what combination of numbers will allow all of the atoms' numbers to be the same across the reaction arrow.

You can start by adding coefficients to each term:

a*N3 + b*H2 --> c*NH3

You can actually now set up an equation to relate the coefficients to each other:

In terms of nitrogen:

3a = c (no b term because there is no nitrigen in hydrogen)

In terms of hydrogen:

2b = 3c (no a term because azide has no hydrogen!)

Well, these two equations give us a pretty nice relation in that 3a = c. We can substitute for c in the second equation using (3a) as a result.

2b = 3(3a)


2b = 9a

Now, remembering that a = 3c, we get a sort of symmetric equation:

2b = 9a = 3c = k

So, all we'd need to do is select a number that gives us the least-common-multiple for each number. This is the k that we're setting all three expresions to. In other words, for this equation, we'll need to find the LCM for 2, 3, and 9. This number ends up being 18, so we can solve for a, b, and c by setting up the three equations that result from our setting the symmetric equation to 18.

2b = 18

3c = 18

9a = 18

We can find fairly quickly that a = 2, b = 9, and c = 6

Now, we can just plug in those coefficients to find our balanced chemical equation:

2(N3) + 9(H2) --> 6NH3

I hope that helps!


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lebstar3 | Student, Grade 11 | (Level 1) Honors

Posted February 1, 2012 at 11:40 AM (Answer #2)

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the answer is 2(N3)+9(H2)---->6NH3 because there has to be 6 nitrogen on each side and 18 hydrogens on each side to make it equal.

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maria-vivanco | Student, Grade 11 | (Level 1) Valedictorian

Posted January 28, 2014 at 9:25 PM (Answer #3)

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 N3+H2 --> NH3

The order that you balance equations is :

  • metals
  • non- metals
  • hydrogen
  • oxygen

In this equation you would balance Nitrogen first (non metal) 

So then you would get 


the reason why you would add the co-efficient to the compound on the right side of the equation is because on the left side, nitrogen has a subscript of 3 so you would have to muliply nitrogen on the other side by 3 but you cant just do nitrogen because its part of a compound so you muliply the entire compound by three.

Since its multiplied by 3, that makes hydrogen have nine but on the other side you have 2. So what you do, since 9 is an odd number you make that the coefficent of H2 and double everything else.

You now have


It is now balanced. 

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Jyotsana | Student, Grade 10 | (Level 1) Valedictorian

Posted February 15, 2014 at 1:41 AM (Answer #4)

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Synthesis Reaction

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