In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

An iron nail is placed in a flask of water, which has been boiled to release any dissolved oxygen. The flask is attached to a vacuum pump which removes the air inside it. Then the flask is sealed. Assuming that the explanation of Scientist 1 is correct, which of the following results will be observed?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

An iron nail is placed in a test tube filled with water. Then, a layer of oil is poured over the water. After an extended period of time, no rust is observed to have formed on the iron nail. Scientist 1 would most likely explain this result by saying that:

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Given that all of the following are true, which of the following, if found, provides the strongest evidence against Scientist 1's hypothesis?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Given that all of the following are true, which of the following, if found, provides the strongest evidence against Scientist 2's hypothesis?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Lye (sodium hydroxide) is a base that neutralizes acids. Suppose that lye is added to water in which an iron pipe has been immersed. According to Scientist 2, the pipe's rate of rusting will most likely __________.

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

An iron nail is placed in an unsealed test tube filled with water. No other substances are added to the water. When the nail is removed after an extended period of time, it is covered by rust. According the Scientist 2, the nail most likely rusted because __________.

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Sodium hydroxide (NaOH) is a compound which dissociates into Na⁺ and OH^- ions in solution. Suppose that sodium hydroxide is added to water in which a piece of iron has been immersed. It is then observed that the rate at which rust forms on the iron increases. Scientist 1 would most likely explain this result by saying that __________.

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

According to Scientist 1, which of the following conditions will result in the least rapid formation of rust?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Given that the explanation of Scientist 2 is correct, which of the following conditions, if any, will result in the formation of rust?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Bromothymol blue is a pH indicator that is yellow in acidic solutions and blue in basic solutions. When bromothymol blue is added to a solution, it remains blue. A piece of iron is then immersed in this solution. Given that the explanation of Scientist 2 is correct, which of the following is most likely to occur?