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Questions and Answers

What type of corrosion occurs when two different metals are in contact with each other in the presence of an electrolyte?

Crevice corrosion

Galvanic corrosion (correct)

Localized corrosion

Uniform corrosion

Which metal is stated to have a greater tendency to corrode than iron but does not suffer problematic corrosion?

Zinc

Iron

Copper

Aluminum (correct)

What is the primary reason that iron corrosion leads to continuous degradation compared to aluminum corrosion?

Iron oxide flakes off, exposing fresh iron. (correct)

Aluminum oxide is more corrosive.

Iron reacts more slowly with oxygen.

Iron oxide forms a protective layer.

Which term describes the degradation of metals by chemical reactions with their environment?

Corrosion Signup and view all the answers

Which type of corrosion is associated with small gaps between two pieces of metal?

Crevice corrosion Signup and view all the answers

What are reactions that involve the transfer of electrons between reactants called?

Oxidation-reduction reactions Signup and view all the answers

What is the notable characteristic of rust formation in terms of its process?

It is a slow process. Signup and view all the answers

Why is it important to distinguish between primary and secondary batteries?

They are used in different applications and have different benefits. Signup and view all the answers

What is the primary role of the salt bridge in a galvanic cell?

To allow ions to flow between the half-cells. Signup and view all the answers

Which ion flows into the Ag+ half-cell when using a salt bridge with NH4Cl?

NH4+ Signup and view all the answers

In the cell notation for a galvanic cell, what does the double vertical line (||) represent?

The salt bridge connection. Signup and view all the answers

Which statement correctly describes the anode in a galvanic cell?

It is where oxidation occurs. Signup and view all the answers

What is the voltage potential measured for the galvanic cell described with Cu and Ag?

0.46 V Signup and view all the answers

At what concentration is an electrochemical cell considered to be in its standard state?

1 M Signup and view all the answers

What happens at the anode when oxidation occurs?

Cations dissolve into solution, leaving a negative charge. Signup and view all the answers

Which of the following is a characteristic of electrodes in galvanic cells?

They conduct electricity, facilitating oxidation or reduction. Signup and view all the answers

What occurs at the cathode during electrochemical processes?

Cations are removed from solution resulting in a positive charge. Signup and view all the answers

What is a significant factor contributing to the Dreamliner's need for lithium-ion batteries?

Increased fuel efficiency requiring weight minimization. Signup and view all the answers

What is defined as the cell potential or electromotive force (EMF)?

The maximum work obtainable from an electrochemical cell. Signup and view all the answers

What are the primary materials used in the electrodes of lithium-ion batteries?

Graphite and cobalt oxide. Signup and view all the answers

What happens if a salt bridge is not present in an electrochemical cell?

Local charges build up, preventing electrode reactions. Signup and view all the answers

Which property of lithium contributes to the high energy density of lithium-ion batteries?

High standard reduction potential of Li+/Li. Signup and view all the answers

In galvanic corrosion, what role does tin plating play when exposed to air and moisture?

It facilitates the oxidation of iron. Signup and view all the answers

Which of the following describes uniform corrosion?

It requires a nonmetal to be present in the second half-cell. Signup and view all the answers

What challenge do high temperatures pose for lithium-ion batteries?

They cause batteries to degrade quickly. Signup and view all the answers

What is necessary for the corrosion of iron to occur in water?

Water facilitates ion mobility between regions. Signup and view all the answers

What is the role of carbon in lithium-ion batteries?

It is part of the anode where lithium intercalates. Signup and view all the answers

How can the corrosivity of various plated steels be determined?

Through their cell potential. Signup and view all the answers

What results from the exposure of a scratched tin-plated steel can?

Rapid corrosion of the exposed steel occurs. Signup and view all the answers

What does a voltmeter measure regarding electrical potential?

The size of the electrical potential and its polarity Signup and view all the answers

How does reversing the poles of a battery affect the voltage reading on a voltmeter?

It changes the sign of the measured voltage Signup and view all the answers

What characteristic potential is assigned to the Standard Hydrogen Electrode (SHE)?

0 V Signup and view all the answers

Which half-cell notation represents the Standard Hydrogen Electrode (SHE)?

Pt(s) | H2(g, 1 atm) | H+(1 M) Signup and view all the answers

What does the measurement of standard cell voltages suggest about half-reactions?

A specific potential can be associated with a particular half-reaction Signup and view all the answers

In a galvanic cell with the SHE, what role can the SHE take?

Can function as either the anode or the cathode Signup and view all the answers

Which of the following statements about oxidation in a galvanic cell is true?

Oxidation occurs at the anode, releasing electrons Signup and view all the answers

What is the effect of connecting the anode to the positive terminal of a voltmeter?

A negative potential is measured Signup and view all the answers

What is the role of the cathode in an electrochemical cell?

It consumes electrons and undergoes reduction. Signup and view all the answers

What does a positive potential indicate when the SHE is connected to the positive terminal?

Reduction of H+(aq) to H2 occurs. Signup and view all the answers

What happens to the reading on the voltmeter if the leads are reversed?

The sign of the reading changes. Signup and view all the answers

How are standard reduction potentials typically represented?

As half-reactions at 1 M concentration. Signup and view all the answers

What must be done when converting a standard reduction potential to an oxidation half-reaction?

The half-reaction must be reversed and the potential sign changed. Signup and view all the answers

If the half-reaction has a negative standard reduction potential, what does that indicate about the reaction?

The half-reaction is more favorable as an oxidation. Signup and view all the answers

Which of the following statements is true regarding the standard reduction potentials of half-reactions?

The reduction potential signifies the tendency to undergo oxidation or reduction. Signup and view all the answers

Which component in a galvanic cell is responsible for the flow of electrons?

The external circuit connecting the electrodes. Signup and view all the answers

Study Notes

Galvanic Corrosion

Occurs when two dissimilar metals are in contact in the presence of an electrolyte.
The metal with a more negative standard reduction potential will corrode preferentially.

Aluminum Corrosion

Aluminum has a greater tendency to corrode than iron but does not suffer problematic corrosion.
Aluminum oxide (Al2O3) forms a protective layer that prevents further corrosion.

Iron Corrosion

Iron corrodes continuously because the iron oxide (rust) layer is porous and does not protect the underlying metal.

Corrosion

Corrosion is the degradation of metals by chemical reactions with their environment.

Crevice Corrosion

Crevice corrosion occurs in small gaps between two pieces of metal due to the concentration of corrosive species within the confined space.

Redox Reactions

Reactions involving the transfer of electrons between reactants are called redox reactions.

Rust Formation

Rust forms through a complex series of electrochemical reactions.
It involves the oxidation of iron to iron ions and the reaction of these ions with oxygen and water to form hydrated iron oxide (rust).

Batteries

It is important to distinguish between primary and secondary batteries because primary batteries are not rechargeable, while secondary batteries are.

Salt Bridge

The primary role of the salt bridge in a galvanic cell is to maintain electrical neutrality by allowing the flow of ions between the half-cells.

Ion Flow

When using a salt bridge with NH4Cl, the NH4+ ion flows into the Ag+ half-cell.

Cell Notation

In the cell notation for a galvanic cell, the double vertical line (||) represents the salt bridge or other porous barrier separating the half-cells.

Anode

The anode in a galvanic cell is the electrode where oxidation occurs.

Galvanic Cell Potential

The voltage potential for a galvanic cell described with Cu and Ag is +0.46 V.

Standard State

An electrochemical cell is considered to be in its standard state when all reactants and products are at a concentration of 1 M and the temperature is 25°C.

Oxidation

When oxidation occurs at the anode, electrons are released and flow through the external circuit to the cathode.

Electrodes

Electrodes in galvanic cells are typically made of metals or other conductive materials.
They provide a surface for the redox reactions to take place.

Cathode

The cathode in electrochemical processes is the electrode where reduction occurs.

Lithium-Ion Battery (LIB)

The Dreamliner's need for LIBs is due to their high energy density and lightweight design.

Cell Potential

Cell potential or electromotive force (EMF) is defined as the potential difference between the two electrodes of an electrochemical cell.

Lithium-Ion Battery Electrodes

The primary materials used in the electrodes of LIBs are lithium compounds, such as lithium cobalt oxide (LiCoO2) and graphite.

Salt Bridge Absence

If a salt bridge is not present in an electrochemical cell, the cell will not function properly.
Without the salt bridge, the buildup of charge in the half cells would create a potential difference that would prevent the flow of electrons.

Lithium Battery Energy Density

Lithium's high energy density in LIBs is attributed to its low atomic weight and high electrochemical potential.

Tin Plating in Galvanic Corrosion

Tin plating serves as a protective layer on steel.
When exposed to air and moisture, tin, being more anodic than steel, corrodes preferentially, protecting the steel underneath.

Uniform Corrosion

Uniform corrosion describes the even, gradual corrosion of a metal surface.

Lithium-Ion Battery Temperature

High temperatures can degrade LIBs by accelerating chemical reactions and causing electrolyte decomposition.

Iron Corrosion in Water

For iron corrosion to occur in water, the presence of an electrolyte (such as dissolved salts) and oxygen is necessary.

Carbon in LIBs

Carbon plays a vital role in LIBs, acting as the anode material.
It provides a framework for lithium ions to intercalate and deintercalate during charging and discharging.

Plated Steel Corrosivity

The corrosivity of different plated steels can be determined by using standard electrochemical techniques like the Tafel extrapolation method or cyclic voltammetry.

Scratched Tin-Plated Steel

When exposed to air and moisture, a scratched tin-plated steel can will show localized corrosion at the scratch.
The steel will corrode preferentially at the exposed area because tin is more anodic than steel.

Voltmeter Measurement

A voltmeter measures the potential difference between two points in an electrical circuit.

Battery Poles Reversal

Reversing the poles of a battery will reverse the voltage reading on a voltmeter.

Standard Hydrogen Electrode (SHE)

The SHE is assigned a standard potential of 0.00 V.

SHE Half-Cell Notation

The half-cell notation for the SHE is Pt(s) | H2 (g, 1 atm) | H+ (aq, 1 M).

Standard Cell Voltages

Measurement of стандартных стандартных потенциалов указывает на то, что каждая полуреакция имеет стандартный потенциал независимо от других полуреакций, которые могут быть объединены с ней.

SHE in Galvanic Cells

The SHE can serve as either the cathode or anode in a galvanic cell, depending on its connection to the other half-cell.

Oxidation in Galvanic Cells

In a galvanic cell, oxidation always occurs at the anode, and the electrons flow from the anode to the cathode.

Anode to Voltmeter Positive Terminal

Connecting the anode to the positive terminal of a voltmeter will result in a positive voltage reading.

Cathode Role

The cathode in an electrochemical cell is the electrode where reduction occurs.
It gains electrons from the anode through the external circuit.

Positive Potential with SHE

A positive potential when the SHE is connected to the positive terminal indicates that the other half-cell has a higher standard reduction potential than the SHE.

Reversed Voltmeter Leads

If the leads of the voltmeter are reversed, the reading will change sign but maintain the same magnitude.

Standard Reduction Potentials

Standard reduction potentials are typically represented as E° values, where the value is negative or positive, indicating the tendency of the half-reaction to occur spontaneously as a reduction.

Oxidation Potential Conversion

Converting a standard reduction potential to an oxidation half-reaction requires reversing the sign of the potential.

Negative Standard Reduction Potential

A negative standard reduction potential indicates that the reaction prefers to occur as an oxidation, rather than a reduction.

Standard Reduction Potential Comparison

The standard reduction potentials of half-reactions provide information about their relative tendencies to undergo reduction under standard conditions.
Half-reactions with more positive standard reduction potentials are more likely to occur as reductions.

Electron Flow in Galvanic Cells

The external circuit, connecting the anode and cathode in a galvanic cell, is responsible for the flow of electrons.
Electrons flow from the anode (where oxidation occurs) to the cathode (where reduction occurs).

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