Battery and Fuel Cell Quiz

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Questions and Answers

What is the voltage of a typical dry cell battery?

2.04 V

1.5 V (correct)

1.25 V

1.23 V

Which battery type utilizes lead and lead dioxide as electrodes?

Nickel-Cadmium

Fuel Cell

Lead Storage Battery (correct)

Dry Cell

What is one disadvantage of the dry cell battery?

Low energy efficiency

Irreversible side reactions (correct)

High rechargeability

Complex construction

In the hydrogen-oxygen fuel cell, what is produced when hydrogen is oxidized?

Electrons Signup and view all the answers

Which of these batteries is rechargeable?

Both A and C Signup and view all the answers

What is the combined voltage generated from two NiCd cells connected in series?

+2.50 V Signup and view all the answers

What is the net voltage of the Lead Storage Battery?

+2.04 V Signup and view all the answers

Which substance is used to convert hydrocarbons into hydrogen for fuel cells?

Reformers Signup and view all the answers

What is the first step in balancing a half-reaction using oxidation numbers?

Assign oxidation numbers. Signup and view all the answers

In the balancing of the half-reaction 4 H+(aq) + 3 e– + CrO42-(aq) → CrO2-(aq) + 2 H2O(l), what is the oxidation number change for Chromium?

+6 to +4 Signup and view all the answers

When balancing the electrons lost and gained during a redox reaction, what must be true?

Electrons lost must equal electrons gained. Signup and view all the answers

Which of the following best describes the process of separating the net equation into two half-reactions?

Isolate the oxidation and reduction half-reactions. Signup and view all the answers

In the example balancing the reaction CrO42-(aq) + SO32-(aq) → CrO2-(aq) + SO42-(aq), what is the role of the sulfate ion?

It undergoes oxidation. Signup and view all the answers

What is indicated by a line connecting the reducing agent to its corresponding product?

The oxidation state change. Signup and view all the answers

In the step to check if all elements and charges are balanced after simplification, what are you primarily verifying?

Both atoms and charges must be balanced. Signup and view all the answers

What should be done after balancing the substances that change in oxidation number?

Join the oxidizing and reducing agents with lines. Signup and view all the answers

What does electrochemistry primarily study?

Electron transfer in chemical reactions Signup and view all the answers

Which of the following statements correctly defines oxidation?

It is the loss of electrons. Signup and view all the answers

In a redox reaction, what must be true about the electrons involved?

The number of electrons lost equals the number of electrons gained. Signup and view all the answers

What is the role of a reducing agent in a redox reaction?

It loses electrons and causes reduction. Signup and view all the answers

Which of the following half-reactions represents reduction?

Fe3+(aq) + 3e− → Fe(s) Signup and view all the answers

What does the term 'spectator ions' refer to in redox reactions?

Ions that do not change and remain in solution Signup and view all the answers

In the half-reaction Na(s) → Na+(aq) + 1e−, what is being oxidized?

Na(s) Signup and view all the answers

How can you determine the net ionic equation from half-reactions?

By excluding spectator ions and combining the oxidation and reduction half-reactions. Signup and view all the answers

Study Notes

Oxidation Numbers (States)

An oxidation number is the apparent charge of an atom in a neutral molecule or charged polyatomic ion.
Oxidation numbers are used to identify if oxidation or reduction is occurring in a molecular compound without ion charges.
A decrease in oxidation number represents reduction.
An increase in oxidation number represents oxidation.

Rules for Assigning Oxidation Numbers

Pure elements: The oxidation number is zero.
Simple ions: The oxidation number is equal to the ion charge.
Hydrogen in most compounds: The oxidation number is +1. (Exception: metal hydrides, eg, LiH, where hydrogen is -1.)
Oxygen in most compounds: The oxidation number is -2. (Exception: peroxides eg, H₂O₂, Na₂O₂, where oxygen is -1.)
Sum of oxidation numbers: The sum of oxidation numbers of all atoms in a substance must equal the substance's net charge (zero for compounds and the charge of the polyatomic ion).
Molecular compounds (no H or O): The more electronegative element is assigned an oxidation number equal to the negative charge it usually has in ionic compounds.

Example Calculations

N in N₂O: Individual oxidation numbers are +1 and -2; the sum is zero.
C in C₂H₂OH: Individual oxidation numbers are -2, +1, -2, and +1 which sum to zero.
P in P₂O₅: Individual oxidation numbers are +5 and -2; the sum is zero.

Redox Reactions

Oxidation numbers help identify if a reaction is a redox reaction.
A redox reaction involves both an increase and a decrease in oxidation numbers.
Example (Ag(s) + NaNO₃(aq) → Na(s) + AgNO₃(aq)): Silver (Ag) is oxidized because its oxidation number increased, and Sodium (Na) is reduced because its oxidation number decreased.

Electrochemistry

Electrochemistry: The branch of chemistry studying electron transfer in chemical reactions.
Oxidation: Loss of electrons (LEO).
Reduction: Gain of electrons (GER).
Oxidation and reduction always occur together in redox reactions.
Half-reactions describe the oxidation and reduction processes.
Spectator ions do not change in a redox reaction.
The substance reduced is the Oxidizing Agent (OA).
The substance oxidized is the Reducing Agent (RA).

Spontaneous Redox Reactions

Spontaneous redox reactions occur without external energy input.
The strongest oxidizing agent (SOA) is on top-left of the table.
The strongest reducing agent (SRA) is on bottom-right of the table.
A redox reaction is spontaneous if the oxidizing agent (OA) is above the reducing agent (RA) in the table of half reactions.

Predicting Redox Reactions

List all reactants
Dissociate soluble ionic compounds and acids
Do not dissociate molecular compounds
Include H⁺ ions if acidic
Always include water (H₂O)

Short-Hand Notation

A shorthand notation is used to represent a voltaic or electrolytic cell.
A line (/) separates items in different phases (solid, liquid, gas, or aqueous solution).
A double line (//) represents a salt bridge or porous cup.
Commas separate items in the same phase.

Drawing Electrochemical Cells

When drawing a cell, label the cathode, anode, positive terminal, negative terminal, electrolytes, and the directions of cation and anion flow.
Show and label reduction half-reaction, oxidation half-reaction, net reaction, Eº values, Eº net, and spontaneity.

Commercial Cells (Batteries)

Batteries are made of multiple voltaic cells connected in series.

Dry Cells

1.5V and 9V batteries in clocks, remote controls, etc.

Nickel-Cadmium Batteries

Rechargeable.

Lead Storage Batteries

Typical car batteries.

Fuel Cells

Continuous supply of reactants.
Example: Hydrogen-oxygen fuel cells.

Electrolytic Cells (Basics)

Use electrical energy to force a nonspontaneous chemical reaction to occur.
Typically used to electroplate metals, recharge batteries, and split compounds into useful gases.

Quantitative Study of Electrolysis

Stoichiometry is applied to electrolytic reactions.
Charge (q) is in Coulombs(C).
One mole of electrons carries 9.65 x 10⁴ C (Faraday Constant, F).
Moles of electrons (nₑ) = (current(I) x time(t)) ÷ (Faraday constant(F)).

Titrations

A titration is a procedure to determine the volume of one substance needed to completely react with another.
Common oxidizing agents in redox titrations are permanganate and dichromate ions (because of their color change).
The equivalence point is reached when the titrant (oxidizing agent) has completely reacted with the sample (reducing agent).
The concentration of the titrant must be accurately known and standardized against a primary standard.

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Description

Test your knowledge on battery types, their components, and fuel cells with this quiz. Questions cover dry cell batteries, lead storage batteries, and hydrogen-oxygen fuel cells. Perfect for students and enthusiasts in the field of electrochemistry.