Question 1

How might electrolysis be used to raise the hull of a sunken ship?

Accepted Answer

The gaseous products of the electrolysis of water can be collected and used to inflate large bags attached to the hull of the sunken ship. As the bags inflate, they exert upward pressure and buoy the ship upward.

Question 2

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

By connecting a metal like iron with a wire to a metal that is easier to oxidize like zinc, the other metal (zinc) is oxidized instead and the electrons travel to the iron, keeping it from oxidizing. This process is known as sacrificial protection, as the less noble (more easily oxidized) metal sacrifices itself to protect the more noble (less easily oxidized) metal. This is why zinc is often used as a protective coating on iron or steel.

Question 3

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

Water's oxygen is chemically bound to hydrogen, making it unavailable for combustion. Additionally, the oxygen in water is not in the form of O2, which is needed for fire.

Question 4

Why is oxygen usually an oxidizing agent?

Accepted Answer

Oxygen is a highly electronegative element, meaning it has a strong attraction for electrons. This makes it more likely to accept electrons, which is the definition of oxidation.

Question 5

A chemical equation for the combustion of propane, C₃H₈, is shown below. Through this reaction is the carbon oxidized or reduced? C₃H₈ + 5O₂ → 3 CO₂ + 4 H₂O

Accepted Answer

In the reaction, the carbon in propane (C3H8) combines with oxygen to form carbon dioxide (CO2). In this process, carbon gains oxygen and loses electrons, indicating that it has been oxidized.

Question 6

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

Since iron atoms have a greater tendency to oxidize than copper, they will lose electrons to copper atoms in the plumbing system. These copper atoms will then pass those electrons to oxygen atoms in contact with the surface of the pipes, leading to oxidation and corrosion. This can be detrimental to the plumbing system and may cause leaks. Therefore, this is bad news for a home with iron and copper pipes connected together.

Question 7

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 so much of a problem. Why?

Accepted Answer

Aluminum oxide is insoluble in water and forms a protective coating that prevents continued oxidation of the aluminum. This makes it less of a problem for structural engineers compared to the oxidation of iron to rust, which can lead to significant weakening of the material.

Question 8

Jewelry is often manufactured by electroplating an expensive metal such as gold over a cheaper metal. A setup for this process can be sketched as follows:  What would happen if the battery connections were suddenly reversed?

Accepted Answer

The answer of Jewelry is often manufactured by electroplating an...

Question 9

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

Copper has a greater tendency to be reduced than iron, meaning it will gain electrons from iron in the presence of an electron acceptor such as oxygen. This can lead to accelerated corrosion around the interface of the two metals, which is not good news for the Statue of Liberty's exterior made of copper held together by steel rivets.

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 cathodic region?}

Accepted Answer

In this reaction, water is being split into hydrogen ions (H+) and hydroxide ions (OH-), leading to the formation of FeS2O3 (rust). At the cathodic region, oxygen is being reduced, gaining electrons and reacting with the hydrogen ions to form water. This reaction helps to prevent further oxidation of the iron, but can lead to corrosion of the cathodic region if the conditions are not carefully controlled.

Question 11

Why are combustion reactions generally exothermic?

Accepted Answer

The answer of Why are combustion reactions generally exothermic?
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Question 12

Sodium metal is

Accepted Answer

The answer of Sodium metal is
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Question 13

How many electrons are transferred from iron atoms to oxygen atoms in the formation of two molecules of iron hydroxide, Fe(OH)₂?

Accepted Answer

In the formation of Fe(OH)₂, each iron (Fe) atom transfers 2 electrons to oxygen. For two molecules, 2 Fe atoms transfer a total of 4 electrons.

Question 14

Why is the formation of iron hydroxide, Fe(OH)₂, from Fe²⁺ and OH^- not considered an oxidation-reduction reaction?

Accepted Answer

In an oxidation-reduction reaction, there must be a transfer of electrons between the reacting species. Fe²⁺ is not changed during the reaction, which means there is no transfer of electrons and hence no oxidation-reduction reaction occurs.

Question 15

A major source of chlorine gas, Cl₂, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq). Which of the following is the balanced chemical reaction for this electrolysis reaction?

Accepted Answer

The balanced chemical reaction for the electrolysis of brine is: 2 NaCl (aq) + 2 H2O → 2 NaOH (aq) + Cl2 (g) + H2 (g).

Question 16

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

In an electrochemical cell, the anode is where oxidation occurs. In the given reaction, iron is being oxidized and losing electrons to form Fe2+ ions. Therefore, the correct answer is A) Iron is being oxidized.

Question 17

A major source of chlorine gas, Cl₂, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq). What is the sign of the electrode where the chlorine gas is formed? Is it negative or positive?

Accepted Answer

Chlorine gas is formed at the positive electrode (anode) where chloride ions lose electrons (oxidation) to form chlorine molecules.

Question 18

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 19

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 thin, protective layer on the surface of the metal that prevents further corrosion. This layer is more stable and adherent than the rust that forms on iron, which tends to flake off and expose more metal to corrosion.

Question 20

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.

Quiz 18: Two Classes of Chemical Reactions

How might electrolysis be used to raise the hull of a sunken ship?

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?

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?

Why is oxygen usually an oxidizing agent?

A chemical equation for the combustion of propane, C₃H₈, is shown below. Through this reaction is the carbon oxidized or reduced? C₃H₈ + 5O₂ → 3 CO₂ + 4 H₂O

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.

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 so much of a problem. Why?

Jewelry is often manufactured by electroplating an expensive metal such as gold over a cheaper metal. A setup for this process can be sketched as follows: What would happen if the battery connections were suddenly reversed?

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?

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 cathodic region?}

Why are combustion reactions generally exothermic?

Sodium metal is

How many electrons are transferred from iron atoms to oxygen atoms in the formation of two molecules of iron hydroxide, Fe(OH) ₂?

Why is the formation of iron hydroxide, Fe(OH) ₂, from Fe²⁺ and OH^- not considered an oxidation-reduction reaction?

A major source of chlorine gas, Cl₂, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq) . Which of the following is the balanced chemical reaction for this electrolysis reaction?

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?}

A major source of chlorine gas, Cl₂, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq) . What is the sign of the electrode where the chlorine gas is formed? Is it negative or positive?

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?

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

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

Quiz 18: Two Classes of Chemical Reactions

How might electrolysis be used to raise the hull of a sunken ship?

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?

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?

Why is oxygen usually an oxidizing agent?

A chemical equation for the combustion of propane, C3H8, is shown below. Through this reaction is the carbon oxidized or reduced? C3H8 + 5O2 → 3 CO2 + 4 H2O

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.

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 so much of a problem. Why?

Jewelry is often manufactured by electroplating an expensive metal such as gold over a cheaper metal. A setup for this process can be sketched as follows: What would happen if the battery connections were suddenly reversed?

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?

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 cathodic region?

Why are combustion reactions generally exothermic?

Sodium metal is

How many electrons are transferred from iron atoms to oxygen atoms in the formation of two molecules of iron hydroxide, Fe(OH) 2?

Why is the formation of iron hydroxide, Fe(OH) 2, from Fe2+ and OH- not considered an oxidation-reduction reaction?

A major source of chlorine gas, Cl2, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq) . Which of the following is the balanced chemical reaction for this electrolysis reaction?

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?

A major source of chlorine gas, Cl2, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq) . What is the sign of the electrode where the chlorine gas is formed? Is it negative or positive?

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?

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

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

A chemical equation for the combustion of propane, C₃H₈, is shown below. Through this reaction is the carbon oxidized or reduced? C₃H₈ + 5O₂ → 3 CO₂ + 4 H₂O

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 cathodic region?}

How many electrons are transferred from iron atoms to oxygen atoms in the formation of two molecules of iron hydroxide, Fe(OH) ₂?

Why is the formation of iron hydroxide, Fe(OH) ₂, from Fe²⁺ and OH^- not considered an oxidation-reduction reaction?

A major source of chlorine gas, Cl₂, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq) . Which of the following is the balanced chemical reaction for this electrolysis reaction?

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?}

A major source of chlorine gas, Cl₂, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq) . What is the sign of the electrode where the chlorine gas is formed? Is it negative or positive?