As with any combustion reaction, the products of combusting a hydrocarbon fuel $(C_x{H}_y)$ with oxygen $(O_2)$ are carbon dioxide $(C{O}_2)$ and water $(H_{2}O).$

A mass of $18\mathrm{.}12g$ for an unknown fuel was combusted in a reaction vessel containing an unknown amount of oxygen. At the end of the reaction, there still remained $18\mathrm{.}07g$ of the fuel as

well as $0\mathrm{.}0817g$ of water and $0\mathrm{.}1497g$ of carbon dioxide. The oxygen was completely consumed during the reaction.

How many molecules of oxygen gas were initially present in the reaction vessel?

Express the number of molecules to three significant digits.

View Available Hint$($s$)$

amount of $O_2=$

molecules