Question

When the following reaction is balanced with the lowest possible whole number coefficients, what is the coefficient in front of oxygen (O2)?

C2H6 + O2 yields CO2 + H2O

A) 2
B) 3
C) 5
D) 7

Answer 1

1) Equation: C2H6 + O2 → CO2 + H2O

2) Balanced equation: 2C2H6 + 7O2 → 3CO2 + 6H2O

Proof

                     left side          right side

Element

C                  2*2 = 4             4

H                  2*6 = 12           6*2 = 12

O                 7*2 = 14           4*2+6 = 14

Then, the coefficient in front of O2 is 7.

Answer: option D) 7