Your reaction will produce 14 g of carbon dioxide.
Start with the balanced chemical equation for the combustion of ethyne
Notice that you have a
Use oxygen gas' molar mass to determine how many moles of oxygen react
Since ethyne is in excess, all the available moles of oxygen will react. This means that the number of moles of carbon dioxide the reaction will produce will be equal to
Use carbon dioxide's molar mass to see how many grams you'd get
Rounded to two sig figs, the number of sig figs you gave for the mass of oxygen, the answer will be