Question

A major component of gasoline is octane (C₈H₈). When liquid octane is burned in air it reacts with oxygen (O₂) gas to produce carbon dioxide gas and water vapor. Calculate the moles of water produced by the reaction of 1.8 mol of octane. Be sure your answer has a unit symbol, if necessary, and round it to 2 significant digits. 

Answer 1

Solution :

Chemical reaction occuring during combustion of liquid octane to yield carbon dioxide and water vapours -

C3H18 (1) + O2(g) →xC02(g) + xH20 (9)

Balanced chemical reaction -

2C3H18 (1) +2502(9) 16C02(9) + 18H20 (9)

Since, octane is undergoing complete combustion ( burning with air) to yield end products carbon dioxide and water, hence, octane is limiting reagent itself.

Hence, amount of products formed will depend upon octane only.

Therefore, according to chemical equation of reaction occuring,

2 moles of octane produces 18 moles of water

Hence, 1 mol of octane will produce =

(18 ÷ 2 ) moles of water

= 9 moles of water.

Hence,

1.8 moles of octane will produce =

(9 × 1.8) moles of water

= 16.2 moles of water. ( 3 significant figures)

~ 16 mol of water ( 2 significant figures ) (Answer)