When the equation C2H4+O2—>CO2+H2O is balanced using smallest whole numbers, what is the coefficient of the O2?

The coefficient that has been added as the coefficient to oxygen has been 3. Thus, option C is correct.

The balanced equation has been given with the number of atoms for each element for the reactants and products have been equal.

The given equation has been consisting of 2 oxygen atoms on the reactant side, while 3 oxygen atoms on the product side.

The equal number of oxygen atoms on the product and reactant side has been given by adding coefficient 3 at the oxygen atom on the reactant side.

Thus, option C is correct.

For more information about the balanced equation, refer to the link:

link

The answer to your question is letter C. 3

Explanation:

Unbalanced chemical reaction

                     C₂H₄   +   O₂    ⇒    CO₂   +   H₂O

                   Reactants      Elements    Products

                        2                     C                  1

                        4                     H                  2

                        2                     O                  3

Balanced chemical reaction

                      C₂H₄   +   3O₂    ⇒    2CO₂   +   2H₂O

                   Reactants      Elements    Products

                        2                     C                  2

                        4                     H                  4

                        2                     O                  6

The coefficient of Oxygen is three.