A chemical equation is shown:

C2H4 + O2 → CO2 + H2O

According to the law of conservation of mass, how many atoms of oxygen exist in the products of this reaction?

5

6

7

8

C2H4 + O2 → CO2 + H2O

eqn is unbalanced - balancing by counting no. of C n H atoms

C=2 n H=4 in one C2H4

so the reaction will form two CO2 + two H2O

counting no. of O atoms: 2*2 + 2*1

=4+2

=6

Given unbalanced chemical equation: C2H4 + O2 → CO2 + H2O

Before applying conservation of mass, the equation must be balanced:

C2H4 + xO2 → 2CO2 + 2H2O

With 2CO2 + 2H2O as the final products, there are 2x2 + 2x1 = 6 O atoms.

The answer is 6.