Answer:
- From octane: 
- From ethanol: 
Explanation:
Hello,
At first, for the combustion of octane, the following chemical reaction is carried out:

Thus, the produced mass of carbon dioxide is:

Now, for ethanol:


Best regards.
Answer:
oil floats on water because it is heavier than water
Salt is no longer visible after stirring as salt dissolves in water
by filtration