Finding moles in a reaction

Question

In the reaction if N2 with H2 to form NH3, how many moles of H2 are needed to react with 2 moles of N2? Show each step

Answer 1

Hi!

The first thing you have to do is write out the equation: N₂ + H₂ ---> NH₃

Next, you need to balance the equation so there are equal N & H on both sides: N₂ + 3H₂ ---> 2NH₃

Now you can set up the problem. To find the number of moles of H₂ when there are 2 moles of N₂ you have to know stoichiometry.

We start with what the question gives us: 2 moles of N₂

The next step will be to cancel our units which are moles of N₂. This is where our balanced equation will come in handy. You will use the balanced equation so you have a ratio of H₂ to N₂. The ratio comes from the coefficients (the numbers in front).

N₂ + 3H₂ ---> 2NH₃ The ratio in this question would be 3 mol of H₂ for every 1 mol of N₂

**Remember that if there is no number present, we assume it is a 1, thus 1 mol of N₂

2 mol N₂ x 3 mol H₂ Our mol of N₂ are opposite each other so they will cancel out

1 1 mol N₂ leaving us with our desired units of mol H_2.

Next, we just need to solve the equation like you would solve any fraction. 2 x 3 = 6 6/1 = 6

Therefore, our answer is: We need 6 mol of H₂ for every 2 mol of N₂

I hope this helps!