There's a slight error in your equation. I think you were trying to present it like this:
2C8H18 + 25O2 -> 16CO2 + 18H2O
Mole Ratio
O2 : H20
25 : 18
? moles : 18 moles
(18/18)×25 : 18 moles
25 moles : 18 moles
Final answer would be 25 moles of O2. :)
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The equation is: C+O2=>CO2
Since we got 10 molecules of CO2 new balanced equation would be 10C+10O2=>10CO2
from this equation we can see that we have 10 molecules of oxygen, however ,we need to find atoms. There are 2 atoms in the oxygen molecule so we need to multiply 10 by 2 which gives us 20 atoms.
The answer: there are 20 atoms of oxygen
Answer:
a)
,
, b)
, 
Explanation:
a) The ideal gas is experimenting an isocoric process and the following relationship is used:

Final temperature is cleared from this expression:


The number of moles of the ideal gas is:



The final temperature is:


The final pressure is:



b) The ideal gas is experimenting an isobaric process and the following relationship is used:

Final temperature is cleared from this expression:




The final volume is:



Carbon = 12.010. Oxygen = 15.999 x 2 15.999 x 2 = 31.998 + 12.010 = 44.008 \frac{37.15 grams * 1 mole CO2}{44.008 grams}