Question 1

Upon combustion, about how many grams of water vapor are produced from every 16 grams of methane,  ? 
 + 2  →  + 2  O

Accepted Answer

According to the balanced equation, for every 16 grams of methane, 2 moles of water are produced. The molar mass of water is 18 g/mol (2x 1.008 g/mol + 15.999 g/mol). Therefore, 2 moles of water weigh 36 grams. So, for every 16 grams of methane, 36 grams of water vapor are produced upon combustion.

Question 2

Why are combustion reactions generally exothermic?

Accepted Answer

The answer of Why are combustion reactions generally exothermic?
...

Question 3

One of the products of combustion is water. Why doesn't this water extinguish the combustion?

Accepted Answer

The water produced during combustion is in the form of steam or water vapor, which is in the gaseous phase. This means it doesn't stay in contact with the fire to extinguish it but instead floats away from the heat source.

Question 4

Copper atoms have a greater tendency to be reduced than iron atoms do. Was this good news or bad news for the Statue of Liberty, whose copper exterior was originally held together by steel rivets?

Accepted Answer

The greater tendency of copper to be reduced than iron means that in the presence of an electrolyte, electrons will preferentially flow from the iron to the copper and then onto oxygen. This accelerated corrosion around the interface of the two metals could lead to damage to the Statue of Liberty's copper exterior held together by steel rivets.

Question 5

How many electrons are transferred from iron atoms to oxygen atoms in the formation of two units of iron hydroxide, Fe  ?

Accepted Answer

The answer of How many electrons are transferred from iron...

Question 6

Why is the air over an open flame always moist?

Accepted Answer

When a flame combusted, it reacts with oxygen to produce heat, light, and various products, one of which is water vapor. This makes the air above the flame more moist compared to the surrounding air. Option A is incorrect because the flame does not vaporize water in the air, it forms water vapor as one of the products of combustion. Option C is also incorrect because humidity is the amount of water vapor in the air, and warm air can hold more moisture than cold air, but it does not necessarily mean that warm air contains more humidity than cold air.

Question 7

Why is the formation of iron hydroxide, Fe  , from  and O  not considered an oxidation-reduction reaction?

Accepted Answer

An oxidation-reduction reaction involves the transfer of electrons between two species. In this reaction, the Fe ion is only reacting with O to form Fe(OH)3, and the 11ea7cc8_da65_f5c6_a2ab_0d05fb3dc5f6_TB2711_11 ion is not involved and remains unchanged. Therefore, this is not an oxidation-reduction reaction.

Question 8

Why might coating a metal with another metal that is easier to oxidize prevent the first metal from being oxidized?

Accepted Answer

The answer of Why might coating a metal with another...

Question 9

How would connecting iron with a wire to a piece of metal like copper, which undergoes reduction very easily, affect the rate at which the iron corrodes?

Accepted Answer

When iron is connected to a more easily reducible metal like copper, it acts as the anode while the copper acts as the cathode. This creates a potential difference between the two metals and results in an increased flow of electrons from the iron to the copper. This causes accelerated corrosion of the iron, as more electrons are available for the oxidation reaction. Thus, connecting iron with a wire to a piece of copper would increase the rate of corrosion of the iron.

Question 10

Rust has a tendency to form when iron in contact with water reacts according to the following reaction: 4 Fe + 3 O₂ → 2 Fe₂O₃ _{What is happening at the anodic region?}

Accepted Answer

At the anodic region, iron is oxidized, which means it loses electrons and forms Fe2+ ions. This oxidation reaction occurs as a result of the flow of electrons from the anode to the cathode during the corrosion process.

Question 11

Upon entering the body, are drugs gradually oxidized or reduced?

Accepted Answer

Drugs are primarily metabolized in the liver through oxidation, which is a major pathway for drug metabolism.

Question 12

How does connecting a metal like iron with a wire to a metal that is easier to oxidize like zinc help prevent corrosion of the iron?

Accepted Answer

Connecting the iron with a wire to the metal that is easier to oxidize like zinc creates a galvanic cell, where the other metal (zinc) acts as an anode and undergoes oxidation instead of the iron. The electrons generated during the oxidation of zinc move through the wire to the iron, which acts as a cathode, preventing it from undergoing oxidation.

Question 13

Why might coating a metal with another metal that is harder to oxidize prevent the first metal from being oxidized?

Accepted Answer

Coating a metal with another metal that is harder to oxidize creates a physical barrier on the surface of the metal. This barrier prevents moisture and oxygen from coming into contact with the metal, which helps to prevent the metal from being oxidized. The metal that is coated is protected from the environment, and therefore does not react.

Question 14

Aluminum metal undergoes the same basic corrosion process that iron does yet it does not decompose as rapidly. Why?

Accepted Answer

Aluminum oxide forms a protective layer on the surface of the metal which prevents further corrosion. Unlike rust, the aluminum oxide does not flake off and expose fresh metal to further corrosion.

Question 15

Iron atoms have a greater tendency to oxidize than do copper atoms. Is this good news or bad news for a home in which much of the plumbing consists of iron and copper pipes connected together? Explain.

Accepted Answer

The greater tendency of iron atoms to oxidize means they will lose electrons to the copper atoms, which will then facilitate the transfer of those electrons to oxygen atoms in contact with the surface. This process, known as galvanic corrosion, can lead to corrosion and damage to the pipes over time. Therefore, it is bad news for a home where iron and copper pipes are connected together.

Question 16

A chemical equation for the combustion of propane, C₃H₈, is shown below. Through this reaction is the carbon oxidized or reduced? + 5 → 3 + 4 O

Accepted Answer

In the combustion of propane, carbon combines with oxygen to form carbon dioxide. Since the carbon has gained oxygen, it has undergone oxidation. Therefore, the correct answer is A.

Question 17

Water is 88.88 percent oxygen by mass. Oxygen is exactly what a fire needs to grow brighter and stronger. So why doesn't a fire grow brighter and stronger when water is added to it?

Accepted Answer

The answer of Water is 88.88 percent oxygen by mass....

Question 18

The oxidation of iron to rust is a problem structural engineers need to be concerned about, but the oxidation of aluminum to aluminum oxide is not. Why?

Accepted Answer

Aluminum oxide is insoluble in water and forms a protective coating over the surface of aluminum, preventing further oxidation from occurring. This protective layer is why aluminum is considered to be a highly corrosion-resistant material, unlike iron which continues to corrode without a protective layer.

Quiz 11: Oxidations and Reductions Charge the World

Upon combustion, about how many grams of water vapor are produced from every 16 grams of methane, ? + 2 → + 2 O