Question #ec791

1 Answer
Apr 17, 2016

Alas, you are wrong.


Here are some tips:

  1. You got the right number of moles of nitrogen. But for hydrogen you should use a molecular weight of 2 not 6.

  2. You do not add up the moles together. Rather you divide the number of moles of hydrogen by the coefficient 3 in the reaction equation, and divide the number of moles of nitrogen by 1. Whichever is smaller corresponds to the limiting reagent.

  3. Then you take the smallest quotient (the one corresponding to the limiting reagent) and multiply by 2 which is the coefficient of #NH_3# in the products of the reaction equation. That gives the number of moles of #NH_3#.

  4. Multiply the number of moles of #NH_3# by the given #\DeltaH# to get the energy requirement. Note that you get a negative number, meaning energy is actually released.

  5. Learn more than just answering the problem. Read about the Haber process for making ammonia at

It's actually more complicated than just the one reaction because you need other reactions to make the hydrogen. That is where you really require energy (more than you can get from just the hydrogen reacting with the nitrogen).

Hope this helps! :-)