CHM112 chapter 21
Calculate Ecell for the concentration cell represented by: Zn (s)|Zn2+ (aq, 0.100 M)||Zn2+ (aq, 1.00 M)|Zn (s).
+0.030 V
Anode Cathode Overall
2H2 (g) → 4H+ (aq) + 4e- O2 (g) + 4H+ (aq) + 4e- → 2H2O (g) 2H2 (g) + O2 (g) → 2H2O (g)
Anode Cathode Overall
2H2O (l) → O2 (g) + 4H+ (aq) + 4e- 2H2O (l) + 2e- → 2OH- (aq) + H2 (g) 2H2O (l) → O2 (g) + 2H2 (g)
When the two half-reactions below are added together (ensuring that the electrons cancel), which of the following is the net reaction? Reaction 1: Cu2+ + 2e- → Cu Reaction 2: Fe → Fe3+ + 3e-
3Cu2+ + 2Fe → 3Cu + 2Fe3+
By definition, if one coulomb of charge passes between two electrodes that differ in potential by one volt, one of energy is released. This relationship is correctly expressed as V = /. (Fill in units only, without values.)
Blank 1: joule or J Blank 2: joule or J Blank 3: C or coulomb
The Nernst equation is used to calculate the cell potential under conditions. The cell potential is found to differ from the standard cell potential by a factor proportional to the natural log of the reaction (Q).
Blank 1: nonstandard, non-standard, non standard, or nonstandard-state Blank 2: quotient
Which of the following options currently express the relationship between the charge passing through an electrochemical cell and the current flowing? Select all that apply.
C = A x s current (A) = charge/time
Fe2+ Al Reducing agent is Oxidizing agent is NO3-
Species reduced Species oxidized Al Fe2+ Spectator ion
Select the statements that correctly describe a concentration cell. Select all that apply.
The electrode and the electrolyte are the same materials in both half-cells. The cell emf is generated because of a difference in concentration. A concentration cell spontaneously generates electricity.
Ni2+ (aq) Ni (s)
Oxidizing agent Reducing agent
Which of the following factors increase the rate of corrosion of iron? Select all that apply.
Increasing the temperature Increasing electrolyte concentration
In a lithium-ion battery, lithium ions migrate from the _____ to the _____ in order to balance the total charge as electrons pass through the external circuit.
anode; cathode
In a voltaic cell, electrons are generated due to the oxidation reaction at the _____ and flow through the external circuit toward the _____.
anode; cathode
Alkaline batteries adopted their name from the _____ that is present in the reactions at both the zinc anode and the MnO2 cathode.
hydroxide ion
A(n) ______ electrode is composed of a material that does not directly take part in an electrochemical reaction (other than transmitting electrons) while a(n) ______ electrode does participate in a half-reaction.
inactive; active
The Faraday constant is the charge (in coulombs) of ______.
one mole of electrons
The difference between the calculated voltage (based on standard potentials) and the actual voltage required to cause electrolysis is called ______.
overvoltage
When predicting the spontaneous reaction between two different half-cells, the reaction with the most negative cell potential will be the _____ reaction, while the reaction with the most positive cell potential will be the _____ reaction.
oxidation; reduction
A disc of platinum used for: Pt2+ (aq) + 2e- → Pt (s) Platinum wire used for: 2Cl- (aq) → Cl2 (g) + 2e-
Active platinum electrode Inactive platinum electrode
Ag+ (aq) + e- → Ag (s); Eo = +0.799 V Co2+ (aq) + 2e- → Co (s); Eo = -0.277 V Fe2+ (aq) + 2e- → Fe (s); Eo = -0.440 V Rank the species in order of increasing strength to act as an reducing agent from weakest at the top of the list to strongest at the bottom of the list.
Ag Co Fe
Consider the following oxidation reactions: Cu (s) → Cu2+ (aq) + 2e-; Eo = -0.337 V Cd (s) → Cd2+ (aq) + 2e-; Eo = 0.403 V Ag (s) → Ag+ (aq) + e-; Eo = -0.799 V Which is the most active metal?
Cd
In which of the following reactions is chlorine reduced? Select all that apply.
Cl2 + 2Na → 2NaCl 2NaClO + F2 → NaF + Cl2 + O2
Co3+ (aq) + Cu (s) → Co2+ (aq) + Cu+ (aq) Calculate the standard cell potential for the reaction above given the following information: Co3+ (aq) + e- → Co2+ (aq); Eo = 1.842 V Cu+ (aq) + e- → Cu (s); Eo = 0.521 V
+1.321 V
When hydrogen atoms are balanced in the following (unbalanced) half-reaction, identify the amount of the substance that must be introduced, and where it will appear in the equation. Assume the reaction occurs in acidic medium. 2ClO3- → Cl2 + 6H2O
12 H+ must be added as a reactant.
Identify the number of water molecules needed to balance the following half-reaction. Also indicate whether the water will appear as a reactant or a product. MnO4- → MnO2
2 H2O; product
What is the spontaneous reaction that occurs when the following half-cells are combined? Zn2+ (aq) + 2e- → Zn (s); Eo = -0.76 V Na+ (aq) + e- → Na (s); Eo = -2.71 V
2Na (s) + Zn2+ (aq) → 2Na+ (aq) + Zn (s)
The Faraday constant allows one to convert between moles of and the equivalent amount of charge in units of . Listen to the complete question
Blank 1: electrons Blank 2: coulombs, C, or coulomb
To which of the following half-reactions must 2 electrons appear as products in order to balance the equation?
H2 + 2OH- → 2H2O H2O + PbO → PbO2 + 2H+
Which of the following correctly describe the electrolysis of water? Select all that apply.
Hydrogen gas is generated at the cathode. An electrolyte such as Na2SO4 is required for this reaction.
In which of the following (unbalanced) half-reactions will 1 mole of water appear as a reactant when oxygen atoms are balanced? Select all that apply.
Na → NaOH N2O5 → 2NO3
1.00 moles of Zn and 0.500 moles of Zn2+ ions in 1.00 L of solution are used to form one half-reaction cell, while 2.00 moles of Cu and 3.00 moles of Cu+ in 1.00 L of solution are used to form a second half-reaction cell. The equation for the overall cell reaction is given by Zn (s) + 2Cu+ (aq) → Zn2+ (aq) + 2Cu (s). Which of the following values are correct based on the information provided if the temperature is 298 K and Eo = 0.91 V? Select all that apply.
Q = 0.0556 E = 0.95 V
Ca (s) Ca2+ (aq) Pb (s) Pb2+ (aq)
Reactant in anode compartment Product in anode compartment Product in cathode compartment Reactant in cathode compartment
Ecell > 0 Ecell < 0 Ecell = 0
Reaction is spontaneous. Reaction is nonspontaneous. Reaction is at equilibrium.
A sacrificial anode can be used to protect a metal like iron from corrosion. In order for this to work, the anode must be _____ than the metal that it is protecting.
more active
If a change in reaction conditions causes the standard cell potential (Eo) of an electrochemical reaction become more negative, the standard free energy change (ΔGo) will become _____ and the equilibrium constant (Keq) will become _____.
more positive; smaller
A lead-acid car battery requires an ______ to recharge. These batteries are typically charged at 12.9 V to 14.1 V, whereas the discharging voltage is 12 V.
overvoltage
Highly active metals are easily _____. Therefore, they are generally found as products in half-reactions with _____ standard reduction potentials.
oxidized; negative
A species acts as a(n) _____ agent if it gains electrons in a half-reaction. Conversely, it could potentially act as a(n) _____ agent if it loses electrons in a half-reaction.
oxidizing; reducing
If a substance acts as a strong oxidizing agent, it will appear on a table of standard reduction potentials as the _____ in a half-reaction with a _____ standard reduction potential.
reactant; positive
Common forms of ______ are: E = Eo - 0.0592Vn0.0592Vn log Q (at 298 K) E = Eo - RTnFRTnF ln Q
the Nernst equation
Identify general features of an alkaline battery. Select all that apply.
The anode is Zn powder. The anode and cathode are separated by a porous barrier.
Identify general features of a lead-acid battery. Select all that apply.
The solid reaction products adhere to the electrodes, making the electrode reactions reversable. The acid is typically sulfuric acid in these types of batteries. The negative electrode is made of spongy lead.
When water is hydrolyzed in the presence of NaCl, the possible half-cell equations are given in the accompanying table. Experimentally, it is found that H2 (g) and Cl2 (g) are formed, while O2 (g) and Na (s) are not. What is the best explanation for this?
There is a significant overvoltage associated with the oxidation of water to form oxygen.
Calcium is plated onto an electrode through the reduction reaction Ca2+ (aq) + 2e- → Ca (s). Which equation would be used to calculate the mass of calcium that is deposited in 30.0 seconds at using a current of 2.0 A?
(2.0A)(30.0s)(40.1g Camol Ca)(96,500C1mol e−)(2mol e−1mol Ca)
A standard electrochemical cell is constructed from an anode that has a standard reduction potential of -2.0 V and a cathode that has a standard reduction potential of +0.5 V. Which of the following is the correct expression to calculate the standard cell potential?
+0.5 + 2.0
Given that the standard potential for the half-reaction Ag+ (aq) + e- → Ag (s) is +0.80 V, calculate the standard reduction potential for the half-reaction 2Ag+ (aq) + 2e- → 2Ag (s).
+0.80 V
Fe (s) + Hg22+ (aq) → Fe2+ (aq) + 2Hg (l); Eo = 1.229 V Hg22+ (aq) + 2e- → 2Hg (l); Eo = +0.789 V Using the standard cell potential given above and the standard reduction potential listed above, calculate the standard reduction potential for the half-reaction Fe2+ (aq) + 2e- → Fe (s).
-0.440 V
As the name implies, nickel-metal hydride batteries involve metal hydrides. Hydrides are found in compounds such as NaH, CaH2, etc. What is the oxidation state of hydrogen in this type of compound? (Hint: consider the suffix of the name.)
-1
Ca (s) + Mg2+ (aq) → Ca2+ (aq) + Mg (s); Eocell = 0.50 V Mg2+ (aq) + 2e- → Mg (s); Eomagnesium = -2.37 V Using the standard cell potential given above and the standard reduction potential listed above, calculate the reduction potential of the half-reaction Ca2+ (aq) + 2e- → Ca (s).
-2.87 V
Given that the standard potential for the half-reaction Ca2+ (aq) + 2e- → Ca (s) is -2.87 V, what is the standard potential for the half-reaction 2Ca2+ (aq) + 4e- → 2 Ca (s)?
-2.87 V
Ag (s) + Li+ (aq) → Ag+ (aq) + Li (s) Calculate the standard cell potential for the above reaction given the following information: Li+ (aq) + e- → Li (s); Eo = -3.05 V Ag+ (aq) + e- → Ag (s); Eo = 0.799 V
-3.849 V
The cell potential for the standard hydrogen electrode (SHE) is by definition equal to ______ and is used as the reference for other half-cells.
0.00 V
Identify the number of electrons required to balance the following half-reaction. Also indicate whether these electrons must appear as reactants or products. 2H+ + NO3- → NO2 + H2O
1 e-, reactant
The following redox reaction has been balanced in an acidic solution: 2H+ + 3TeO32- + 4Sb → 3Te + 4SbO2- + H2O Select the correct option that correctly describes the balanced equation in a basic solution after all resulting species are combined and/or canceled correctly.
1 mole of H2O appears on the left side of the equation. 2 moles of OH- appear on the right side of the equation.
Which compounds or solutions are in an appropriate state for the measurement of Ecello for the reaction given below? Select all that apply. Cu2+ (aq) + H2 (g) → Cu (s) + 2H+ (aq)
1.0 M Cu2+ H2 gas at 1 atm
When hydrogen atoms are balanced in the following (unbalanced) half-reaction, identify the amount of the substance that must be introduced, and where it will appear in the equation. Assume the reaction occurs in acidic medium. 2ClO3- → Cl2 + 6H2O Multiple choice question.
12 H+ must be added as a reactant.
Prior to balancing oxygen and hydrogen atoms, identify the missing coefficients in the half-reaction _____ NO2- → _____ NH4+.
1; 1
When the half-reactions below are balanced to each other, the first reaction should be multiplied by ____ and the second reaction should be multiplied by ____. Equation 1: 2H2O → O2 + 4H+ + 4e- Equation 2: Ni2+ + 2e- → Ni
1; 2
Identify the missing coefficient to balance Mn in the following half-reaction (do not worry about balancing the oxygen atoms). Mn2O3 → _____ MnO2
2
When calcium ions (Ca2+) are electrolytically reduced to calcium metal, what is the relationship between the moles of electrons transferred and the moles of Ca (s) produced?
2 mol of e- will be transferred for every 1 mol Ca (s) produced.
It is easy to forget to consider the number of electrons that take part in an electrochemical reaction when solving for the product of electrolysis. If 6 moles of electrons are consumed during the reduction of Fe3+ to form Fe (s), how many moles of iron are formed?
2 moles Fe
The reaction shown below occurs in a basic solution. Select all the options that correctly describe the balanced equation obtained after all resulting species are combined and/or canceled correctly. MnO2 + 4H+ + Zn → Mn2+ + 2H2O + Zn2+
2 moles of H2O appear among the reactants. 4 moles of OH- appear among the products.
When the half-reactions below are balanced to each other, the first reaction should be multiplied by ____ and the second reaction should be multiplied by _____. Reaction 1: Cr2O72- + 14H+ + 6e- → 2Cr3+ + 7H2O Reaction 2: S + 3H2O → H2SO3 + 4H+ + 4e-
2; 3
Which of the following electrochemical reactions are spontaneous under standard conditions? Select all that apply.
2Co (s) + 3Cl2 (g) → 2CoCl3 (aq); Ecello = 1.6 V 2Cr (s) + 3Sn4+ (aq) → 2Cr3+ (aq) + 3Sn2+ (aq); Ecello = 0.89 V
An aqueous solution of CuBr2 is placed in an electrolytic cell. Which of the following reactions may occur at the cathode? Select all that apply.
2H2O (l) + 2e- → H2 (g) + 2OH- (aq) Cu2+ (aq) + 2e- → Cu (s)
When hydrogen and oxygen atoms are balanced in the following half-reaction under acidic conditions, which of the following statements are correct? Select all that apply. TiO2 (s) → Ti (s)
4 moles of H+ appear as a reactant. 2 moles of H2O appear as a product.
Which of the following are true when the reactions below are added together? Make sure you eliminate species that appear on both sides of the equation. Reaction 1: 2BiO+ + 4H+ + 6e- → 2Bi + 2H2O Reaction 2: 6H2O → 3H2O2 + 6H+ + 6e-
4 moles of H2O appear as a reactant 2 moles of H+ appear as a product
Select the active electrodes among the following choices.
A sodium wire used for: Na (s) → Na+ (aq) + e- A disc of platinum used for: Pt2+ (aq) + 2e- → Pt (s) A strip of zinc used for: Zn2+ (aq) + 2e- → Zn (s)
What is the spontaneous reaction that occurs when the two half-cells below are combined? Fe3+ (aq) + e- → Fe2+ (aq); Eo = 0.77 V Ag+ (aq) + e- → Ag (s); Eo = 0.80 V
Ag+ (aq) + Fe2+ (aq) → Ag (s) + Fe3+ (aq)
If we were to solve for the cell potential of the following reaction, which two reactions would we first need to find in a standard reduction table? 2Ag+ (aq) + Zn (s) → 2Ag (s) + Zn2+ (aq)
Ag+ (aq) + e- → Ag (s) Zn2+ (aq) + 2e- → Zn (s)
Pb (s) PbO2 (s)
Anode Cathode
The two electrodes of an electrolytic cell are placed in a sample of molten zinc iodide. After a time, reddish-brown I2 (s) begins to form at one electrode while gray Zn (s) deposits on the other. Which of the following options correctly describe the process occurring? Select all that apply.
At the cathode, Zn2+ ions are reduced to form Zn (s). The half-reaction occurring at the anode is represented by 2I- (l) → I2 (s) + 2e-.
A galvanic cell that is constructed using the same electrode in both half-cells with different concentrations of electrolyte in each is called a(n) cell.
Blank 1: concentration
pH meters, ion selective electrodes, and nerve cells are all examples of the application of cells.
Blank 1: concentration
The deterioration of metals by an electrochemical process is called . The metal is oxidized during this process.
Blank 1: corrosion
The branch of chemistry that deals with the interconversion of electrical and chemical energy is called .
Blank 1: electrochemistry
The process in which electrical energy is used to drive a nonspontaneous electrochemical reaction is called .
Blank 1: electrolysis
An electrode composed of a material that does not directly take part in an electrochemical reaction (other than transmitting electrons) is called a(n) electrode, whereas an electrode that does participate in half-reactions is called a(n) electrode.
Blank 1: inactive, inert, or nonactive Blank 2: active
If the oxidation number of a substance increases (becomes more positive), that substance has been ; if the oxidation number decreases (becomes more negative), that substance has been .
Blank 1: oxidized Blank 2: reduced
If the oxidation number of a substance increases (becomes more positive), that substance has been ; if the oxidation number decreases (becomes more negative), that substance has been . Listen to the complete question
Blank 1: oxidized Blank 2: reduced
If a substance causes another substance to be oxidized, that substance is a(n) agent. Likewise, the substance that is oxidized in an electrochemical reaction is always the agent.
Blank 1: oxidizing Blank 2: reducing
The measure of energy used in electrochemistry is the cell (Ecell), which is the difference in electrical potential between two electrodes. A common term for this difference in electrical potential is force or emf.
Blank 1: potential or voltage Blank 2: electromotive
When a secondary battery is used as a power source, it operates as a(n) cell. When it is being recharged, it operates as a(n) cell.
Blank 1: voltaic or galvanic Blank 2: electrolytic
A(n) cell uses a spontaneous reaction to generate electrical energy. In this type of cell, the system does work on the .
Blank 1: voltaic or galvanic Blank 2: surroundings
The cell potential for the standard hydrogen electrode (SHE) is by definition equal to volts. If this half-cell is used as the anode and all of the substances in the cathode are under standard conditions, then the potential of the cell is equal to the standard potential of the cathode.
Blank 1: zero, 0, 0.0, or 0.00 Blank 2: reduction
Which of the following options correctly describe the processes that occur during electrolysis of an aqueous solution of an electrolyte? Select all that apply.
Both H2O and any negative ions present might be oxidized. Competing reduction and oxidation reactions are possible. The species with the most positive reduction potential will likely be reduced at the cathode.
Which of the following is the proper shorthand notation for the redox reaction 2H+ (aq) + Cu (s) → Cu2+ (aq) + H2 (g)? (The hydrogen half-cell uses a graphite inactive electrode.)
Cu (s) | Cu2+ (aq) || H+ (aq) | H2 (g) | graphite
Which of the following options correctly describe the units used to express electrical potential, charge, and electrical energy? Select all that apply.
Electrical energy can be measured in joules. The volt is the unit for electrical potential.
True or false: For a spontaneous redox reaction, the products are stronger oxidizing and reducing agents than the reactants.
False
After spectator ions are eliminated, which of the listed species should be used when balancing the equation for the following redox reaction? Select all that apply. FeCl2 (aq) + NaOH (aq) + H2 (g) → Fe (s) + NaCl (aq) + H2O (l)
Fe2+ (aq) H2O (l) OH- (aq) H2 (g)
Na+ + e- → Na; Eo = -2.7 V Cl2 + 2e- → 2Cl-; Eo = 1.4 V 2H2O + 2e- → H2 + 2OH-; Eo = -0.4 V O2 + 4H+ + 4e- → 2H2O; Eo = -0.82 V An aqueous NaCl solution is electrolyzed. What are the products at the cathode and anode?
H2 and OH- form at the cathode; Cl2 forms at the anode.
After spectator ions are eliminated, which of the listed species should be used when balancing the equation for the following redox reaction? Select all that apply. KMnO4 (aq) + Na2C2O4 (aq) + H2SO4 (aq) → MnSO4 (aq) + K2SO4 (aq) + Na2SO4 (aq) + CO2 (g)+ H2O (l)
H2O (l) CO2 Mn2+ (aq) MnO4- (aq) C2O42- H+
For the chemical reaction shown below, which of the following (unbalanced) reactions should be used as the starting point for the reduction half-reaction? 2Na + 2H2O → 2NaOH + H2
H2O → H2
q V H E S
Heat Electrochemical potential Enthalpy Internal energy Entropy
Identify general features of a lithium-ion battery. Select all that apply.
Lithium ion batteries produce almost three times the voltage as nickel-metal hydride batteries. The electrodes are separated by an organic electrolyte that allows Li+ to migrate from anode to cathode. These batteries have a very high energy density.
Na+ + e- → Na; Eo = -2.7 V Cl2 + 2e- → 2Cl-; Eo = 1.4 V Consider the reactions occurring in an electrolytic cell at two inactive electrodes immersed in anhydrous molten sodium chloride. Which products form at the cathode and anode?
Na forms at the cathode; Cl2 forms at the anode.
Select applications for concentration cells. Select all that apply.
Nerve cell membranes pH meters Ion-selective electrodes
The reaction below is spontaneous in the forward direction. Which of the statements below provides the best reason for this observation? Ni (s) + 2Ag+ (aq) → Ni2+ (aq) + 2Ag (s)
Ni (s) gives its electrons away more freely than Ag (s).
Given the two half-reactions below, which reaction will be the reduction reaction in the spontaneous reaction that would occur between them? Cr3+ + 3e- → Cr; Eo = -0.74 V Ni2+ + 2e- → Ni; Eo = -0.28 V
Ni2+ + 2e- → Ni
Given the two half-reactions below, which reaction will be the reduction reaction in the spontaneous reaction that would occur between them? Cr3+ + 3e- → Cr; Eo = -0.74 V Ni2+ + 2e- → Ni; Eo = -0.28 V Multiple choice question.
Ni2+ + 2e- → Ni
Which of the following statements correctly describe the reactions occurring in a hydrogen fuel cell? Select all that apply.
O2 (g) is the reactant at the cathode in the fuel cell. H2 (g) is oxidized at the anode.
Which of the following species can be added to balance the H+ ions in a redox reaction occurring in basic medium?
OH-
Which of the following is required to solve for the nonstandard cell potential using the Nernst equation? Select all that apply.
Q, the reaction coefficient E°, the standard cell potential n (the number of electrons in the balanced reaction)
Which of the following reactions result in the oxidation of sulfur? Select all that apply.
SO2 + H2O2 → H2SO4 S8 + 8O2 → 8SO2
Which of the following options correctly describe corrosion? Select all that apply.
Some metals oxidize to form a protective coating, which prevents further corrosion. During corrosion the metal surface supplies both the cathode and the anode. During corrosion, a metal is oxidized.
Which of the following statements correctly describe tabulated standard electrode potentials? Select all that apply.
The best oxidizing agents will be reactants in half-reactions with the most positive cell potentials. If Eo for a given half-reaction is large and positive, the reaction is spontaneous from left to right as written.
Which of the following statements correctly describe standard electrode potentials? In what way must half-reactions and/or electrode potentials be manipulated when writing a balanced equation for a redox reaction?
The half-reaction for the anode must be reversed when writing the balanced equation for the overall reaction. By convention, standard electrode potentials are quoted as reduction potentials.
Which of the following is required in order for an electrochemical reaction to generate an electric current?
The half-reactions must be physically separated.
When zinc metal is immersed in a 1.0 M solution of copper (II) chloride at 25oC, no electrochemical work may be extracted, even though a spontaneous reaction occurs. What is wrong with this cell design?
The oxidation and reduction reactions must be physically separated.
Identify general features of a nickel-metal hydride battery. Select all that apply.
These batteries are commonly found in power tools. The anode reaction is the oxidation of hydrogen atoms absorbed within a metal alloy. The cathode reaction is the reduction of nickel(III) to nickel(II).
True or false: The emf of a concentration cell is derived from a concentration gradient wherein the less concentrated cell acts as the anode and the more concentrated cell acts as the cathode.
True
Based on the following reaction, identify ALL the species that should be included in the oxidation half-reaction equation. Zn (s) + Cu2+ (aq) → Zn2+ (aq) + Cu (s)
Zn (s) Zn2+ (aq)
Oxidation occurs at the Reduction occurs at the
anode. cathode.
The electrode at which the oxidation reaction occurs is called the _____, while the electrode at which the reduction reaction occurs is called the _____.
anode; cathode
An electrochemical is the primary system for the study of electrochemical reactions.
cell
The SI unit of current is the ampere, which is defined as the flow of charge in units of _____ over a period of time measured in _____.
coulombs; seconds
Coating steel with a more active metal is the most effective method to prevent corrosion. The iron remains intact as the cathode while the more active metal oxidizes. When zinc is used as the coating, the process is called ______.
galvanizing
Oxidation involves the _____ of electrons, while reduction involves the _____ of electrons.
loss; gain
Ag+ (aq) + e- → Ag (s); Eosilver = +0.799 V A high, positive reduction potential for a metal cation like Ag+ indicates that silver metal is _____ active.
not very
In practice, a voltage greater than the calculated value is required to perform an electrolytic process. The added voltage is called a(n) ______. It represents additional driving force needed to overcome barriers such as the large activation energy required for a gas to form at the electrode.
overvoltage
As listed in a table of standard electrode potentials, the reactants in the half-reactions are potential _____ agents, while the products of the half-reactions are potential _____ agents.
oxidizing; reducing
If a substance acts as a strong reducing agent, it will appear on a table of standard reduction potentials as the _____ in a half-reaction with a _____ standard reduction potential.
product; negative
An electrochemical cell operates because the electrodes in the two half-cells differ in their electrical potential. A metal electrode composed of ______ reducing agent will have a greater electrical potential to push electrons toward the electrode composed of a ______ reducing agent.
stronger; weaker
In a voltaic cell In an electrolytic cell
the anode is negative and the cathode is positive. the cathode is negative and the anode is positive.
A(n) _____ cell exploits a spontaneous redox reaction to generate electrical energy, whereas a(n) _____ cell requires a continuous input of electrical energy.
voltaic; electrolytic
When a rechargable battery is used as a power source, it operates as a(n) _____ cell. When it is being recharged, it operates as a(n) _____ cell.
voltaic; electrolytic
For a voltaic cell For an electrolytic cell nonspontaneous spontaneous
ΔG < 0 ΔG > 0 electrolytic cell voltaic cell
For a voltaic cell For an electrolytic cell Work is done on the system in a(n) The system does work on the surroundings in a(n)
ΔG < 0. ΔG > 0. electrolytic cell. voltaic cell.
Na F O Ca
+1 -1 -2 (or -1) +2
NaClO4 HCl KClO RbClO3
+7 -1 +1 +5
A concentration cell is constructed based on the equation Ag+ (1.0 M) + Ag (s) → Ag (s) + Ag+ (x M). When a silver electrode is immersed into this cell at 25.0oC and it is tested against a 1.0 M AgNO3/Ag electrode, a 0.250-V cell potential develops. Calculate the concentration of the electrolyte in the anode compartment. E = E°cell - 0.0592n0.0592n log Q
6.03 x 10-5 M
In an electrochemical cell, electrochemical reactions occur at the surface of two that are immersed in a(n) solution.
Blank 1: electrodes Blank 2: electrolyte, ionic, or ion
The cell potential (Ecello) is measured with gases at a pressure of 1 atm, solutions at 1 M, and solids or liquids in their pure states.
Blank 1: standard
Rank the following metals in order of decreasing activity based on the information given. Place the MOST active metal at the top of the list. Ag+ + e- → Ag; Eo = 0.799 V Cd+2 + 2e- → Cd; Eo = -0.403 V Sn2+ + 2e- → Sn; Eo = -0.136 V
Cd Sn Ag
Which of the following are valid forms of the Nernst equation, which relates cell potential under nonstandard conditions to the standard cell potential? Select all that apply.
E = Eo - 0.0592V/n log Q (at 298 K) E = Eo - RT/nF ln Q
Q < K Q = K Q > K
Ecell > 0 Ecell = 0 Ecell < 0
In general, when the concentration of the reactants in an electrochemical reaction is large, and the concentration of products is small, which of the following will be true regarding the relationship between Ecell and Ecello?
Ecell > Ecello
Q < 1 Q > 1 Q = 1
Ecell > Ecello Ecell < Ecello Ecell = Ecello
The approach to balance redox reactions occurring in basic solution is to first balance them as if they were in acidic solution, then count the number of ______ and add this same number of ______ to each side of the half-reaction.
H+ ions; OH- ions
K+ (aq) + e- → K (s); Eo = -2.925 V Hg2+ (aq) + 2e- → Hg (l); Eo = +0.854 V I2 (s) + 2e- → 2I- (aq); Eo = +0.536 V Rank the species in order of increasing strength to act as an oxidizing agent from weakest at the top of the list to strongest at the bottom of the list.
K I Hg
If ΔGo for a reaction is equal to 0, what must be true regarding the equilibrium constant?
K = 1
n F E
Moles of electrons exchanged in the overall reaction Faraday constant Cell potential
Which of the following correctly state factors involved in the corrosion of iron? Select all that apply.
Oxygen must be present. Moisture must be present.
Cation Anion
Reduction Oxidation
Fe (s) Ag+ (aq) Fe2+ (aq) Ag (s)
Stronger reducing agent Stronger oxidizing agent Weaker oxidizing agent Weaker reducing agent
A metal object is to be plated with Cr metal by electrolysis of aqueous Cr2(SO4)3. Determine the number of electrons transferred and the total charge per mole of Cr (s) produced.
The total charge is 3 x 96,500 = 2.90 x 105 C. 3 mol e- per mole of Cr (s)
In the diagram, electrons flow from the _____ electrode to the _____ electrode. Cations flow from the _____ cell to the _____ cell.
Zn; Cu; anode; cathode
If one were to construct an electrochemical cell consisting of two Zn2+/Zn electrodes at two different concentrations, the more concentrated cell will be the _____.
cathode
The standard cell potential may be solved using the equation E o ______ - E o _____. Select all the options that will correctly complete the equation given.
reduction; oxidation cathode; anode
If ΔGo < 0, the reaction is _____ as written; if K < 1, the reaction is _____ as written.
spontaneous; nonspontaneous
