Which formula equation shows a reversible reaction? 2 upper N a plus upper F subscript 2 right arrow 2 upper N a upper F. Upper C a upper C upper O subscript 3 right arrow upper C a upper O plus upper C upper O subscript 2. Upper N upper H subscript 4 upper C l (s) right and left arrows stacked above each other upper N upper H subscript 3 (g) plus upper H upper C l (g). 2 upper H subscript 2 upper O subscript 2 (a q) right arrow with upper P t above it 2 upper H subscript 2 upper O (l) plus upper 2 subscript 2 (g).