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Chapter 3: Problem 9

You may have noticed that water sometimes drips from the exhaust of a car as it is running. Is this evidence that there is at least a small amount of water originally present in the gasoline? Explain.

Short Answer

Expert verified
The presence of water dripping from the exhaust of a car does not necessarily indicate that there was water in the original gasoline. Instead, it shows that water is a natural byproduct of the combustion process. The combustion of hydrocarbons in gasoline, such as octane, produces water vapor as shown in the chemical equation: \[2 \text{ C}_{8}\text{H}_{18} (l) + 25 \text{ O}_{2} (g) \rightarrow 16 \text{ CO}_{2} (g) + 18 \text{ H}_{2}\text{O} (g)\] This water vapor condenses into liquid water in the exhaust system and eventually drips out from the exhaust pipe.

Step by step solution

01

Understand the car's engine chemical reactions

In a car engine, gasoline (primarily composed of hydrocarbons like octane) reacts with oxygen in the air in a process called combustion. This combustion process releases energy in the form of heat and work, which powers the car. The balanced chemical reaction for the combustion of octane is given by: \[2 \text{ C}_{8}\text{H}_{18} (l) + 25 \text{ O}_{2} (g) \rightarrow 16 \text{ CO}_{2} (g) + 18 \text{ H}_{2}\text{O} (g)\] As seen in the above reaction, the products of octane combustion are carbon dioxide (CO₂) and water (H₂O).
02

Examine the water formation in the reaction

From the balanced chemical equation, 18 moles of water are produced for every 2 moles of octane molecules combusted. In reality, complete combustion may not occur in a car's engine due to various factors. However, even in incomplete combustion, a certain amount of water will still form as a byproduct. The water formed during the combustion process is initially in a gaseous state due to the high temperatures within the engine. As the exhaust gases move through the exhaust system and cool down, the gaseous water condenses into liquid form and accumulates in the exhaust. When enough liquid water has gathered, it drips out from the exhaust pipe.
03

Conclude if water was present in gasoline

Given the explanation above, the presence of water dripping from the exhaust of a car does not necessarily indicate that there was water in the original gasoline. Instead, it shows that water is a natural byproduct of the combustion process. Since the combustion of hydrocarbons in gasoline produces water vapor, which then condenses into liquid water, it is normal to observe water dripping from a car's exhaust.

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Most popular questions from this chapter

Considering your answer to Exercise 73 , which type of formula, empirical or molecular, can be obtained from elemental analysis that gives percent composition?

Methane \(\left(\mathrm{CH}_{4}\right)\) is the main component of marsh gas. Heating methane in the presence of sulfur produces carbon disulfide and hydrogen sulfide as the only products. a. Write the balanced chemical equation for the reaction of methane and sulfur. b. Calculate the theoretical yield of carbon disulfide when \(120 . \mathrm{g}\) of methane is reacted with an equal mass of sulfur.

Balance the following equations: a. \(\mathrm{Ca}(\mathrm{OH})_{2}(a q)+\mathrm{H}_{3} \mathrm{PO}_{4}(a q) \rightarrow \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}(s)\) b. \(\mathrm{Al}(\mathrm{OH})_{3}(s)+\mathrm{HCl}(a q) \rightarrow \mathrm{AlCl}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(t)\) c. \(\mathrm{AgNO}_{3}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{Ag}_{2} \mathrm{SO}_{4}(s)+\mathrm{HNO}_{3}(a q)\)

Give the balanced equation for each of the following chemical reactions: a. Glucose \(\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{t}\right)\) reacts with oxygen gas to produce gaseous carbon dioxide and water vapor. b. Solid iron(III) sulfide reacts with gaseous hydrogen chloride to form solid iron(III) chloride and hydrogen sulfide gas. c. Carbon disulfide liquid reacts with ammonia gas to produce hydrogen sulfide gas and solid ammonium thiocyanate \(\left(\mathrm{NH}_{4} \mathrm{SCN}\right)\).

A binary compound between an unknown element \(\mathrm{E}\) and hydrogen contains \(91.27 \% \mathrm{E}\) and \(8.73 \% \mathrm{H}\) by mass. If the formula of the compound is \(\mathrm{E}_{3} \mathrm{H}_{\mathrm{s}}\), calculate the atomic mass of \(\mathrm{E}\).
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