Nitrogen gas reacts with hydrogen gas under high temperature to form ammonia gas.

N₂ + 3H₂ →2 NH₃

This would be your equation; N and H are diatomic molecules so the reactants would be N₂ and H₂ the when they react you have to take into account the charges on each atom so N has a charge of -3 and H + 

so your product from combining N₂ and H₂ becomes NH₃ 

Then make sure the equation is balanced (has equal number of each element on both sides)

Deposition is the transition of matter going from gas to solid without passing through the liquid phase.a.) gas—-> solid

No because it not possibly