Question

what do you observe when ammonia is passed over heated copper oxide

Answer 1

Copper is reduced; nitrogen is oxidized.

Answer 2

When gaseous ammonia is passed over solid copper(II)oxide at high temperatures, nitrogen gas is formed.

2NH3(g)+3CuO(s)=N2(g)+3Cu(s)+3H2O(g)

Also This N2 gas is not pure as it would be in the heating of NaN3 like compounds. (VERY IMPORTANT FOR NEET)