consider the chemical equations shown here. two equations. first: upper c upper h subscript 4 (g) plus 2 upper o subscript 2 (g) right arrow upper c upper o subscript 2 (g) plus 2 upper h subscript 2 upper o (g). second: 2 upper h subscript 2 upper o (g) right arrow 2 upper h subscript 2 upper o (l). what is the equation for the overall reaction obtained by adding these equations?