How does the law of conservation of mass apply to this reaction c2h4 + o2 > 2h2o + 2co2

Only the oxygen needs to be balanced. There are equal numbers of hydrogen and carbon.

1.solid

2.carbon dioxide

3.helium

you did not give any options thus this is the best answer i can give to you with this little information you have given

> they are both natural and not man made

> they can be tracked and predicted by the right tools

-love shrooms