Here's how to balance the equation for the reaction of hydrogen gas (H₂(g)) and nitrogen gas (N₂(g)) to form ammonia gas (NH₃(g)):

1. Write the unbalanced equation:

H₂(g) + N₂(g) → NH₃(g)

2. Balance the nitrogen atoms:

We have 2 nitrogen atoms on the left side (N₂) and 1 on the right side (NH₃). To balance this, we need to put a coefficient of 2 in front of NH₃:

H₂(g) + N₂(g) → 2 NH₃(g)

3. Balance the hydrogen atoms:

Now we have 2 hydrogen atoms on the left and 6 on the right. Put a coefficient of 3 in front of H₂:

3 H₂(g) + N₂(g) → 2 NH₃(g)

The balanced equation is:

3 H₂(g) + N₂(g) → 2 NH₃(g)