Chemistry Chapter 13: Cells and Batteries

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Questions and Answers

What reaction occurs at the anode in an electrolytic cell with cobalt(II) chloride and lead electrodes?

Water is reduced to hydrogen gas.

Chloride ions are oxidized to chlorine gas. (correct)

Cobalt is oxidized to cobalt(II) ions.

Lead is reduced to lead ions.

What is the role of water in the electrolysis of aqueous sodium chloride solutions?

Acts as both an oxidizing and reducing agent. (correct)

Can only reduce sodium ions to sodium metal.

Has no impact on the overall reaction.

Serves exclusively as an oxidizing agent.

Why does chlorine become the strongest reducing agent in the electrolysis of aqueous solutions?

Due to its higher reduction potential compared to water.

Because it is more abundant than sodium ions.

As water becomes a weaker reducing agent under specific conditions. (correct)

Because chlorine can directly substitute for the electrodes.

What minimum voltage is required to initiate the electrolysis of water in aqueous solutions?

0.6 V Signup and view all the answers

What is the implication of the chloride anomaly in aqueous electrolysis?

Chloride ions can become the strongest reducing agent under certain conditions. Signup and view all the answers

What is the role of the copper electrode in a voltaic cell?

It serves as the cathode. Signup and view all the answers

What does SOA stand for in the context of a voltaic cell?

Standard Electrode Potential Signup and view all the answers

Which of the following metals is used as an anode in a voltaic cell?

Zinc Signup and view all the answers

In a voltaic cell, what flows from the anode to the cathode?

Electrons only Signup and view all the answers

What type of electrode must be used with strong oxidizing agents?

Inert electrode Signup and view all the answers

Which of the following is NOT a common inert electrode?

Gold Signup and view all the answers

What must be annotated in a voltaic cell sketch?

Flow of electrons and ions Signup and view all the answers

In the voltaic cell using platinum and lead electrodes, which component is likely to be a solid?

Both electrodes Signup and view all the answers

Which of the following correctly represents the flow of ions in a voltaic cell?

Anions flow to the cathode. Signup and view all the answers

What is the purpose of a conducting pathway in a voltaic cell?

To allow electrons to flow in and out. Signup and view all the answers

What happens to the mass of the anode as a voltaic cell operates?

It decreases due to oxidation. Signup and view all the answers

Which term describes the electrode where reduction occurs?

Cathode Signup and view all the answers

Which step is NOT part of constructing a basic voltaic cell?

Determine the voltage output needed. Signup and view all the answers

During the operation of a voltaic cell, where do the electrons originate?

Anode Signup and view all the answers

What is typically used to connect the half-cells in a voltaic cell?

A salt bridge. Signup and view all the answers

What is the role of the reducing agent in a voltaic cell?

To lose electrons. Signup and view all the answers

What is the function of methanol in the cell described?

It serves as a fuel source to produce hydrogen. Signup and view all the answers

Rusting is an example of what type of reaction?

A redox reaction. Signup and view all the answers

Which metal is known to corrode in a way that forms a protective layer preventing further corrosion?

Aluminium Signup and view all the answers

What is galvanizing?

The method of covering iron with zinc. Signup and view all the answers

In galvanizing, what role does zinc play compared to iron?

Zinc becomes the anode while iron remains intact. Signup and view all the answers

What form does the protective layer take when metals such as aluminum corrode?

Metal oxides. Signup and view all the answers

What is a method to prevent corrosion that uses a sacrificial anode?

Cathodic protection. Signup and view all the answers

What happens to iron when it is galvanized?

It remains while zinc is oxidized. Signup and view all the answers

What is the consequence of rust not adhering well to iron surfaces?

It exposes more iron to the environment. Signup and view all the answers

In corrosion prevention, the process involves applying a coating to protect the underlying metal. Which of the following is NOT a method mentioned?

Electroplating with gold. Signup and view all the answers

What is the primary function of an electrolytic cell?

To use electrical energy to drive a non-spontaneous redox reaction Signup and view all the answers

What type of energy conversion occurs in an electrolytic cell?

Electrical energy into chemical energy Signup and view all the answers

During the operation of an electrolytic cell, what indicates that a redox reaction is taking place?

Bubbles forming at the electrodes Signup and view all the answers

What happens to the cell potential when the direction of a redox reaction is reversed?

It remains the same but reverses its sign Signup and view all the answers

What color change occurs near the electrode from which gas bubbles form when litmus paper is introduced in an aqueous potassium iodide electrolytic cell?

Turns blue indicating a basic solution Signup and view all the answers

What indicates that a negative cell potential denotes a redox reaction in an electrolytic cell?

Energy must be supplied to drive the cell reaction Signup and view all the answers

What is a key visual indicator of a chemical change at the electrodes of an electrolytic cell?

Formation of colored precipitates Signup and view all the answers

Which statement accurately describes a voltaic cell compared to an electrolytic cell?

Voltaic cells generate electricity from spontaneous reactions Signup and view all the answers

What type of reaction does an electrolytic cell facilitate, compared to a voltaic cell?

Non-spontaneous reactions Signup and view all the answers

In terms of energy transformation, electrolytic cells are best described as:

Transformers that convert electrical energy into chemical energy Signup and view all the answers

Study Notes

Chapter 13 - Cells and Batteries

The notes discuss electrochemical cells and batteries.
Humorously illustrated examples are used to introduce the concept of electrochemical batteries.
Voltaic cells: spontaneous redox reactions generate electricity.
Electrodes: conductors that allow electron flow.
Electrolyte: conducting solution.
Oxidation: loss of electrons (occurs at the anode).
Reduction: gain of electrons (occurs at the cathode).
Anode: the electrode where oxidation occurs.
Cathode: the electrode where reduction occurs.
Salt bridge: allows ion flow between half-cells.
Inert electrodes (platinum or carbon): used for solutions that don't involve metal electrodes.

Voltaic Cells

Redox reactions occur within a solution, requiring electron flow.
Conducting solid materials (electrodes) are necessary for electron flow.
An electrolyte completes the circuit through a solution.
Electron flow is external through a connecting wire.
Some voltaic cells use a porous membrane to isolate half-cells.
Most commonly, a salt bridge is used to connect half-cells.

Anodes and Cathodes

Oxidation occurs at the anode.
If the anode is metal, it loses mass as the reaction proceeds.
Negative labels indicate electron origin and loss.
Anions move to the anode.
Reduction occurs at the cathode.
If the cathode is metal, it gains mass as the reaction proceeds.
Positive labels indicate electron gain.
Cations move toward the cathode.

Building Voltaic Cells

Five-step method for assembling voltaic cells with materials that can produce a spontaneous redox reaction.
Step 1: List all oxidation agents (OAs) and reducing agents (RAs).
Step 2: Identify the strongest OA (SOA) and strongest RA (SRA).
Step 3: Reference half-reactions from a data booklet or textbook.
Step 4: Draw a diagram of the voltaic cell and the half cells.
Step 5: A salt bridge connects the half cells.

Cell Notation

Cells have a standard notation to represent their components and direction of ions and electrons.
A single line separates phases.
A double line separates half-reactions (representing a salt bridge/porous cup).
A comma separates species within the same phase.

Cell Potentials

A standard cell contains all components at standard conditions (SATP) with a concentration of 1.0 mol/L.
Ecell = Ecathode-Eanode.
A higher E° indicates a stronger OA.
A lower E° implies a stronger RA.
Positive E° indicates a spontaneous reaction; negative E° indicates a nonspontaneous reaction.

Practicing with Various Cells

Different electrochemical cells exhibit specific properties related to materials (e.g., copper, zinc, silver,chromium).
Different electrolyte solutions affect cell functionality.
Inert electrodes (e.g., platinum) are necessary for certain solutions.

Corrosion

Rusting is a spontaneous redox reaction.
Oxidation half-reaction (anode): Fe → Fe²⁺ + 2e⁻.
Reduction half-reaction (cathode): O₂ + 2H₂O + 4e⁻ → 4OH⁻.
The iron (II) hydroxide undergoes further reaction with oxygen in the air forming iron (III) hydroxide.
Iron (III) hydroxide turns into iron(III) oxide (rust).
Protective layers of metal oxides can prevent corrosion.

Corrosion Prevention

Painting or plating prevents the underlying material from unwanted redox reactions.
Galvanizing coats iron with zinc which becomes the sacrificial anode.
Cathodic protection employs a more easily oxidized ("sacrificial") metal connected to the object to be protected, forcing the object to be the cathode.

Electrolytic Cells

Electrolytic cells use an external power supply to drive nonspontaneous redox reactions.
The process that takes place in an electrolytic cell is called electrolysis.

Voltaic vs. Electrolytic Cells

A comparison highlighting differences in anode, cathode, electron flow, energy source, and spontaneity.

Stoichiometry and Faraday's Law

Electrical current (measured in amperes) and charge (measured in coulombs) can be related quantitatively to electron transfer in half-cells.
Faraday's constant is 9.65 x 10⁴ C/mol e⁻.
Faraday's law states that the amount of a substance changed in an electrolysis reaction is directly proportional to the charge flowing through the circuit.
Electroplating and electrorefining are practical applications of Faraday's law.

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Description

Explore the fascinating world of electrochemical cells and batteries in this quiz covering Chapter 13. Discover key concepts like oxidation, reduction, and the roles of anodes and cathodes, all illustrated with humor. Test your knowledge on how these energy sources work and their important components.