So, if a sample of a compound decomposed to its constituent elements and produced 25.6 g of o, and 9.60 g of carbon, and another sample produced 21.6 g of o, how much carbon was produced in the second sample?

Method 1:
First find out the formula of the sample.
no. of moles of O = 25.6/16 = 1.6
no. of moles of C = 9.6/12 = 0.8
ratio of C:O = 1:2
formula is CO2

In the second sample,
no. of moles of O = 21.6/16 = 1.35
no. of moles of C = 1.35/2 = 0.675
mass of C = 0.675 x12 = 8.1g

method 2:
Actually it’s quite simple. The two samples are the same compound so the elements produced should be in the same ratio.
C/9.6 = 21.6/25.6
C = 8.1g

The answer to the question: choose the correct statement.  a) when ethane reacts with fluorine gas the product is less stable.b) addition reactions of unsaturated hydrocarbons and halogens requires a high activation energy.  c)the double covalent bond within unsaturated hydrocarbons requires a lot of energy to break.  d)the double covalent bond within unsaturated hydrocarbons can be broken easily.is: a) when ethane reacts with fluorine gas the product is less stable.

The answer is 3.