Answer:
2
Step-by-step explanation:
To balance the equation there must be the same numbers of atoms at the left side and at the right side. So, at the left side we have:
6 atoms of H (3 x 2)
2 atoms of N (1 x 2)
And at the right side we have:
1 atom of N (1 x 1)
3 atoms of HN (1 x 3)
If you multiply these last by 2, you will have:
2 atoms of N (2 x 1)
6 atoms of H (2 x 3)
Then, the numbers of atoms of H and N at the left side is equal to the numbers of atoms of H and N at the right side. The balanced equation is:
3H2+N2--> 2NH3