Electrochemistry: Chemical Change and Electrical Work

The overall cell reaction occurring in an alkaline battery is 

${\mathbf{\text{Zn(s) + MnO}}}_{\mathbf{\text{2}}}{\mathbf{\text{(s) + H}}}_{\mathbf{\text{2}}}\mathbf{\text{O(l)}}\mathbf{\to }{\mathbf{\text{ZnO(s) + Mn(OH)}}}_{\mathbf{\text{2}}}\mathbf{\text{(s)}}$

(a) How many moles of electrons flow per mole of reaction? 

(b) If $\mathbf{4}\mathbf{.}\mathbf{50}\mathbf{g}$ of zinc is oxidized, how many grams of manganese dioxide and of water are consumed? 

(c) What is the total mass of reactants consumed in part (b)? 

(d) How many coulombs are produced in part (b)? 

(e) In practice, voltaic cells of a given capacity (coulombs) are heavier than the calculation in part (c) indicates. Explain.

Identify those elements that can be prepared by electrolysis of their aqueous salts: fluorine, manganese, iron, cadmium.

Identify those elements that can be prepared by electrolysis of their aqueous salts: lithium, iodine, zinc, silver.

Identify those elements that can be prepared by electrolysis of their aqueous salts: strontium, gold, tin, chlorine.

Identify those elements that can be prepared by electrolysis of their aqueous salts: copper, barium, aluminum, bromine.

Compare and contrast a voltaic cell and an electrolytic cell with respect to each of the following: 

(a) Sign of the free energy change 

(b) Nature of the half-reaction at the anode 

(c) Nature of the half-reaction at the cathode 

(d) Charge on the electrode labelled “anode” 

(e) Electrode from which electrons leave the cell

In the electrolysis of a molten mixture of RbF and $\mathit{C}\mathit{a}\mathit{C}{\mathit{l}}_{\mathbf{2}}$, identify the product that forms at the negative electrode and at the positive electrode.

In the electrolysis of a molten mixture of NaCl and , identify the product that forms at the anode and at the cathode.

In the electrolysis of a molten mixture of $\mathit{C}\mathit{s}\mathit{B}\mathit{r}$ and $\mathit{S}\mathit{r}\mathit{C}{\mathit{l}}_{\mathbf{2}}$, identify the product that forms at the negative electrode and at the positive electrode.

In the electrolysis of a molten mixture of KI and , identify the product that forms at the anode and at the cathode.

Many common electrical devices require the use of more than one battery. 

(a) How many alkaline batteries must be placed in series to light a flash light with a 6.0-V bulb? 

(b) What is the voltage requirement of a camera that uses six silver batteries?

 (c) How many volts can a car battery deliver if two of its anode/cathode cells are shorted?

What is the direction of electron flow with respect to the anode and the cathode in a battery? Explain.

A concentration cell consists of two $\mathbf{Sn}\mathbf{/}{\mathbf{Sn}}^{\mathbf{2}\mathbf{+}}$ half-cells. The electrolyte in compartment A is 0.13 M $\mathbf{Sn}{\left({\mathbf{NO}}_{\mathbf{3}}\right)}_{\mathbf{2}}$. The electrolyte in B is 0.87M $\mathbf{Sn}{\left({\mathbf{NO}}_{\mathbf{3}}\right)}_{\mathbf{2}}$. Which half-cell houses the cathode? What is the voltage of the cell?

Balance each skeleton reaction, calculate $\mathbf{E}{\mathbf{°}}_{\mathbf{cell}}$, and state whether the reaction is spontaneous:

(a)  ${\mathbf{\text{Cl}}}_{\mathbf{\text{2}}}{\mathbf{\text{(g) + Fe}}}^{\mathbf{\text{2 + }}}{\mathbf{\text{(aq) Cl}}}^{\mathbf{\text{ - }}}{\mathbf{\text{(aq) + Fe}}}^{\mathbf{\text{3 + }}}\mathbf{\text{(aq)}}$

(b)  ${\mathbf{\text{Mn}}}^{\mathbf{\text{2 + }}}{\mathbf{\text{(aq) + Co}}}^{\mathbf{\text{3 + }}}{\mathbf{\text{(aq) MnO}}}_{\mathbf{\text{2}}}{\mathbf{\text{(s) + Co}}}^{\mathbf{\text{2 + }}}\mathbf{\text{(aq)[acidic]}}$

(c) ${\mathbf{\text{AgCl(s) + NO(g) Ag(s) + Cl}}}^{\mathbf{\text{ - }}}{\mathbf{\text{(aq) + NO}}}_{\mathbf{\text{3}}}^{\mathbf{\text{ - }}}\mathbf{\text{(aq)[acidic]}}$

A voltaic cell with Ni/${\text{Ni}}^{\text{2}}$ and Co/C half-cells has the following initial concentrations $\left[{\text{Ni}}^{\text{2 + }}\right]\mathbf{\text{ = 0.80M;}}\left[{\text{Co}}^{\text{2 + }}\right]\mathbf{\text{ = 0.20M}}$.

(a) What is the initial ${\mathbf{\text{E}}}_{\mathbf{\text{cell }}}$?

 (b) What is $\left[{\text{Ni}}^{\text{ + 2}}\right]$ when ${\mathit{E}}_{\mathbf{c}\mathbf{e}\mathbf{l}\mathbf{l}}$ reaches 0.03V? 

(c) What are the equilibrium concentrations of the ions?

What are ${{\mathbf{E}}^{\mathbf{\circ }}}_{\mathbf{c}\mathbf{e}\mathbf{l}\mathbf{l}}$ and $\mathbf{△}{\mathit{G}}^{\mathbf{\circ }}$ of a redox reaction at ${\mathbf{25}}^{\mathbf{0}}\mathit{C}$ for which $\mathit{n}\mathbf{=}\mathbf{1}$ and $\mathit{K}\mathbf{=}\mathbf{5}\mathbf{.}\mathbf{0}\mathbf{\times }{\mathbf{10}}^{\mathbf{6}}$?

A voltaic cell consists of an ${\mathbf{\text{Mn/Mn}}}^{\mathbf{\text{2 + }}}$ half-cell and a ${\mathbf{\text{Pb/Pb}}}^{\mathbf{\text{2 + }}}$ half-cell. Calculate $\left[{\text{Pb}}^{\text{2 + }}\right]$ when $\left[{\text{Mn}}^{\text{2 + }}\right]$ is 1.44M and ${{\mathit{E}}^{\mathbf{\circ }}}_{\mathbf{c}\mathbf{e}\mathbf{l}\mathbf{l}}$ is 0.44V.

What are ${{\mathit{E}}^{\mathbf{\circ }}}_{\mathbf{c}\mathbf{e}\mathbf{l}\mathbf{l}}$ and $\mathbf{△}{\mathit{G}}^{\mathbf{\circ }}$ of a redox reaction at ${\mathbf{25}}^{\mathbf{0}}\mathit{C}$ for which $\mathit{n}\mathbf{=}\mathbf{2}$ and $\mathbf{\text{K = 0.065}}$?

What are ${{\mathbf{E}}^{\mathbf{\circ }}}_{\mathbf{c}\mathbf{e}\mathbf{l}\mathbf{l}}$ and $\mathbf{△}{\mathit{G}}^{\mathbf{\circ }}$ of a redox reaction at ${\mathbf{25}}^{\mathbf{\circ }}\mathit{C}$ for which $\mathit{n}\mathbf{=}\mathbf{2}$ and $\mathit{K}\mathbf{=}\mathbf{65}$?

What are ${{\mathit{E}}^{\mathbf{\circ }}}_{\mathbf{c}\mathbf{e}\mathbf{l}\mathbf{l}}$ and $\mathbf{△}{\mathit{G}}^{\mathbf{\circ }}$ of a redox reaction at ${\mathbf{25}}^{\mathbf{0}}\mathit{C}$ for which $\mathit{n}\mathbf{=}\mathbf{1}$ and $\mathit{K}\mathbf{=}\mathbf{5}\mathbf{.}\mathbf{0}\mathbf{\times }{\mathbf{10}}^{\mathbf{4}}$.

Calculate $\mathbf{△}{\mathit{G}}^{\mathbf{\circ }}$ for each of the reactions

$$\begin{gathered} {\mathbf{\text{(a)Cr(s) and Cu}}}^{\mathbf{\text{2 + }}}\mathbf{\text{(aq)}} \\ {\mathbf{\text{(b)Sn(s) and Pb}}}^{\mathbf{\text{2 + }}}\mathbf{\text{(aq)}} \end{gathered}$$

Calculate $\mathbf{△}{\mathit{G}}^{\mathbf{\circ }}$for each of the reactions 

$$\begin{gathered} {\mathbf{\text{(a)Ag(s) and Mn}}}^{\mathbf{\text{2 + }}}\mathbf{\text{(aq)}} \\ {\mathbf{\text{(b)Cl}}}_{\mathbf{\text{2}}}{\mathbf{\text{(g) and Br}}}^{\mathbf{\text{ - }}}\mathbf{\text{(aq)}} \end{gathered}$$

Calculate $\mathbf{△}{\mathit{G}}^{\mathbf{\circ }}$ for each of the reactions 

$$\begin{gathered} {\mathbf{\text{(a)Al(s) and Cd}}}^{\mathbf{\text{2 + }}}\mathbf{\text{(aq)}} \\ {\mathbf{\text{(b)I}}}_{\mathbf{\text{2}}}{\mathbf{\text{(s) and Br}}}^{\mathbf{\text{ - }}}\mathbf{\text{(aq)}} \end{gathered}$$

Balance the following skeleton reactions and identify the oxidizing and reducing agents: 

(a) ${\mathit{O}}_{\mathbf{2}}\left(g\right)\mathbf{ }\mathbf{+}\mathit{N}\mathit{O}\left(g\right)\mathbf{\to }\mathit{N}{\mathit{O}}_{\mathbf{3}}\left(aq\right)\mathbf{ }\left[acidic\right]$

(b) $\mathit{C}\mathit{r}{\mathit{O}}_{\mathbf{4}}^{\mathbf{2}\mathbf{-}}\left(aq\right)\mathbf{ }\mathbf{+}\mathit{C}\mathit{u}\left(s\right)\mathbf{\to }\mathit{C}\mathit{r}{\left(OH\right)}_{\mathbf{3}}\left(s\right)\mathbf{+}\mathbf{ }\mathit{C}\mathit{u}{\left(OH\right)}_{\mathbf{2}}\left(s\right)\left[basic\right]$

(c) $\mathit{A}\mathit{s}{\mathit{O}}_{\mathbf{4}}^{\mathbf{3}\mathbf{-}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}\mathbf{ }\mathbf{+}\mathit{N}{\mathit{O}}_{\mathbf{2}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}\mathbf{\to }\mathit{A}\mathit{s}{\mathit{O}}_{\mathbf{2}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}\mathbf{ }\mathbf{+}\mathit{N}{\mathit{O}}_{\mathbf{3}}\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}\mathbf{\left[}\mathbf{b}\mathbf{a}\mathbf{s}\mathbf{i}\mathbf{c}\mathbf{\right]}$

Balance the following skeleton reactions and identify the oxidizing and reducing agents:

(a) $\mathbf{ }\mathit{S}\mathit{b}\left(s\right)\mathbf{ }\mathbf{+}\mathit{N}{\mathit{O}}_{\mathbf{3}}^{\mathbf{-}}\left(aq\right)\mathbf{\to }\mathit{S}{\mathit{b}}_{\mathbf{4}}{\mathit{O}}_{\mathbf{6}}\left(s\right)\mathbf{+}\mathbf{ }\mathit{N}\mathit{O}\left(g\right)\left[acidic\right]$

(b) $\mathit{M}{\mathit{n}}^{\mathbf{2}\mathbf{+}}\left(aq\right)\mathbf{+}\mathbf{ }\mathit{B}\mathit{i}{\mathit{O}}_{\mathbf{3}}^{\mathbf{-}}\left(aq\right)\mathbf{\to }\mathit{M}\mathit{n}{\mathit{O}}_{\mathbf{4}}^{\mathbf{-}}\left(aq\right)\mathbf{+}\mathbf{ }\mathit{B}{\mathit{i}}^{\mathbf{3}\mathbf{+}}\left(aq\right)\left[acidic\right]$

(c) $\mathit{F}\mathit{e}{\left(OH\right)}_{\mathbf{2}}\left(s\right)\mathbf{ }\mathbf{+}\mathit{P}\mathit{b}{{\left(OH\right)}_{\mathbf{3}}}^{\mathbf{-}}\left(aq\right)\mathbf{\to }\mathit{F}\mathit{e}{\left(OH\right)}_{\mathbf{3}}\left(s\right)\mathbf{+}\mathbf{ }\mathit{P}\mathit{b}\left(s\right)\left[basic\right]$

Balance the following skeleton reactions and identify the oxidizing and reducing agents:

(a) $\mathit{N}{\mathit{O}}_{\mathbf{2}}\left(g\right)\mathbf{\to }\mathit{N}{{\mathbf{O}}_{\mathbf{3}}}^{\mathbf{-}}\left(aq\right)\mathbf{+}\mathit{N}{\mathit{O}}_{\mathbf{2}}^{\mathbf{-}}\left(aq\right)\left[basic\right]$

(b) $\mathit{Z}\mathit{n}\left(s\right)\mathbf{ }\mathbf{+}\mathit{N}{\mathit{O}}_{\mathbf{3}}^{\mathbf{-}}\left(aq\right)\mathbf{\to }\mathit{Z}\mathit{n}{{\left(OH\right)}_{\mathbf{4}}}^{\mathbf{2}\mathbf{-}}\left(aq\right)\mathbf{ }\mathbf{+}\mathit{N}{\mathit{H}}_{\mathbf{3}}\left(g\right)\left[basic\right]$

(c) ${\mathit{H}}_{\mathbf{2}}\mathit{S}\left(g\right)\mathbf{+}\mathbf{ }\mathit{N}{\mathit{O}}_{\mathbf{3}}^{\mathbf{-}}\left(aq\right)\mathbf{\to }{\mathit{S}}_{\mathbf{8}}\left(s\right)\mathbf{+}\mathbf{ }\mathit{N}\mathit{O}\left(g\right)\left[acidic\right]$

Balance the following skeleton reactions and identify the oxidizing and reducing agents:

(a) $\mathit{A}{\mathit{s}}_{\mathbf{4}}{\mathit{O}}_{\mathbf{6}}\mathbf{(}\mathbf{ }\mathit{s}\mathbf{)}\mathbf{+}\mathit{M}\mathit{n}{\mathit{O}}_{\mathbf{4}}^{\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{\to }\mathit{A}\mathit{s}{\mathit{O}}_{\mathbf{4}}^{\mathbf{3}\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{+}\mathit{M}{\mathit{n}}^{\mathbf{2}\mathbf{+}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{\left[}\mathit{a}\mathit{c}\mathit{i}\mathit{d}\mathit{i}\mathit{c}\mathbf{\right]}$

(b) ${\mathit{P}}_{\mathbf{4}}\mathbf{(}\mathbf{ }\mathit{s}\mathbf{)}\mathbf{\to }\mathit{H}\mathit{P}{\mathit{O}}_{\mathbf{3}}^{\mathbf{2}\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{+}\mathit{P}{\mathit{H}}_{\mathbf{3}}\mathbf{(}\mathbf{ }\mathit{g}\mathbf{)}\mathbf{\left[}\mathit{a}\mathit{c}\mathit{i}\mathit{d}\mathit{i}\mathit{c}\mathbf{\right]}$

(c) $\mathit{M}\mathit{n}{\mathit{O}}_{\mathbf{4}}^{\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{+}\mathit{C}{\mathit{N}}^{\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{\to }\mathit{M}\mathit{n}{\mathit{O}}_{\mathbf{2}}\mathbf{(}\mathbf{ }\mathit{s}\mathbf{)}\mathbf{+}\mathit{C}\mathit{N}{\mathit{O}}^{\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{\left[}\mathit{b}\mathit{a}\mathit{s}\mathit{i}\mathit{c}\mathbf{\right]}$

Balance the following skeleton reactions and identify the oxidizing and reducing agents:

$$\begin{gathered} \mathbf{\text{(a) S}}{{\mathbf{\text{O}}}_{\mathbf{\text{3}}}}^{\mathbf{\text{2 - }}}{\mathbf{\text{(aq) + Cl}}}_{\mathbf{\text{2}}}\mathbf{\text{(g) }}\mathbf{\to }\mathbf{\text{S}}{{\mathbf{\text{O}}}_{\mathbf{\text{4}}}}^{\mathbf{\text{2 - }}}{\mathbf{\text{(aq) + Cl}}}^{\mathbf{\text{ - }}}\mathbf{\text{(aq) [basic]}} \\ \mathbf{\text{(b) Fe(CN}}{{\mathbf{\text{)}}}_{\mathbf{\text{6}}}}^{\mathbf{\text{3 - }}}\mathbf{\text{(aq) + Re(s)}}\mathbf{\to }\mathbf{\text{Fe(CN}}{{\mathbf{\text{)}}}_{\mathbf{\text{6}}}}^{\mathbf{\text{4 - }}}\mathbf{\text{(aq) + Re}}{{\mathbf{\text{O}}}_{\mathbf{\text{4}}}}^{\mathbf{\text{ - }}}\mathbf{\text{(aq) [basic]}} \end{gathered}$$

(C) ${\mathbf{\text{MnO}}}_{\mathbf{\text{4}}}^{\mathbf{\text{ - }}}\mathbf{\text{(aq) + HCOOH(aq)}}\mathbf{\to }{\mathbf{\text{Mn}}}^{\mathbf{\text{2 + }}}{\mathbf{\text{(aq) + CO}}}_{\mathbf{\text{2}}}\mathbf{\text{(g)}}$

Calculate for each of the reactions 

$$\begin{gathered} {\mathbf{\text{(a)Ni(s)andAg}}}^{\mathbf{\text{ + }}}\mathbf{\text{(aq)}} \\ {\mathbf{\text{(b)Fe(s)andCr}}}^{\mathbf{\text{3 + }}}\mathbf{\text{(aq)}} \end{gathered}$$

Define oxidation and reduction in terms of electron transfer and change in oxidation number.

Why must an electrochemical process involve a redox reaction?

Can one half-reaction in a redox process take place independently of the other? Explain

Water is used to balance O  atoms in the half-reaction method. Why can’t ${\mathbf{O}}^{\mathbf{2}\mathbf{-}}$ ions be used instead?

During the redox balancing process, what step is taken to ensure that loss equals gain?

How are protons removed when balancing a redox reaction in a basic solution?

Are spectator ions used to balance the half-reactions of a redox reaction? At what stage might spectator ions enter the balancing process?

Which type of electrochemical cell has  ${\mathbf{\Delta G}}_{\mathbf{sys}\mathbf{ }}\mathbf{<}\mathbf{0}$? Which type shows an increase in free energy?

Which statements are true? Correct any that are false. 

(a) In a voltaic cell, the anode is negative relative to the cathode. 

(b) Oxidation occurs at the anode of a voltaic or electrolytic cell. 

(c) Electrons flow into the cathode of an electrolytic cell. 

(d) In a voltaic cell, the surroundings do work on the system. 

(e) A metal that plates out of an electrolytic cell appears on the cathode. 

(f) The cell electrolyte provides a solution of mobile electrons.

Consider the following balanced redox reaction: 

${\mathbf{\text{16H}}}^{\mathbf{+}}\left(\text{aq}\right)\mathbf{ }\mathbf{+}\mathbf{2}{\mathbf{\text{MnO}}}_{\mathbf{4}}^{\mathbf{-}}\mathbf{+}\left(\text{aq}\right)\mathbf{ }\mathbf{+}\mathbf{10}{\mathbf{\text{Cl}}}^{\mathbf{-}}\left(\text{aq}\right)\mathbf{\to }\mathbf{2}{\mathbf{\text{Mn}}}^{\mathbf{2}\mathbf{+}}\mathbf{+}\left(\text{aq}\right)\mathbf{+}\mathbf{ }\mathbf{5}{\mathbf{\text{Cl}}}_{\mathbf{2}}\left(\text{g}\right)\mathbf{ }\mathbf{+}\mathbf{8}{\mathbf{\text{H}}}_{\mathbf{2}}\mathbf{\text{O}}\left(\text{l}\right)$

(a) Which species is being oxidized? 

(b) Which species is being reduced? 

(c) Which species is the oxidizing agent? 

(d) Which species is the reducing agent? 

(e) From which species to which does electron transfer occur? 

(f) Write the balanced molecular equation, with $\mathbf{\text{K}}{\mathbf{ }}^{\mathbf{+}}\mathbf{\text{and}}\mathbf{ }{\mathbf{\text{SO}}}_{\mathbf{4}}^{\mathbf{2}\mathbf{-}}$ as the spectator ions.

Consider the following balanced redox reaction: 

${\mathbf{\text{2CrO}}}_{\mathbf{2}}^{\mathbf{-}}\left(\text{aq}\right)\mathbf{ }\mathbf{+}\mathbf{2}{\mathbf{\text{H}}}_{\mathbf{2}}\mathbf{\text{O}}\left(\text{l}\right)\mathbf{+}\mathbf{ }\mathbf{6}{\mathbf{\text{ClO}}}^{\mathbf{-}}\left(\text{aq}\right)\mathbf{\to }\mathbf{2}{\mathbf{\text{CrO}}}_{\mathbf{4}}^{\mathbf{2}\mathbf{-}}\left(\text{aq}\right)\mathbf{ }\mathbf{+}\mathbf{3}{\mathbf{\text{Cl}}}_{\mathbf{2}}\left(\text{g}\right)\mathbf{ }\mathbf{+}\mathbf{4}{\mathbf{\text{OH}}}^{\mathbf{-}}\left(\text{aq}\right)$

(a) Which species is being oxidized? 

(b) Which species is being reduced? 

(c) Which species is the oxidizing agent?

(d) Which species is the reducing agent? 

(e) From which species to which does electron transfer occur? 

(f) Write the balanced molecular equation, with the spectator ion.

Balance the following skeleton reactions and identify the oxidizing and reducing agents:

(a) ${\mathbf{\text{ClO}}}_{\mathbf{3}}^{\mathbf{-}}\left(\text{aq}\right)\mathbf{ }\mathbf{+}\mathbf{ }{\mathbf{\text{I}}}^{\mathbf{-}}\left(\text{aq}\right)\mathbf{\to }{\mathbf{\text{I}}}_{\mathbf{2}}\left(\text{s}\right)\mathbf{ }\mathbf{+}{\mathbf{\text{Cl}}}^{\mathbf{-}}\left(\text{aq}\right)\left[\text{acidic}\right]$

(b) ${\mathbf{\text{MnO}}}_{\mathbf{4}}^{\mathbf{-}}\left(\text{aq}\right)\mathbf{ }\mathbf{+}{\mathbf{\text{SO}}}_{\mathbf{3}}^{\mathbf{2}\mathbf{-}}\left(\text{aq}\right)\mathbf{\to }{\mathbf{\text{MnO}}}_{\mathbf{2}}\left(\text{s}\right)\mathbf{ }\mathbf{+}{\mathbf{\text{SO}}}_{\mathbf{4}}^{\mathbf{2}\mathbf{-}}\left(\text{aq}\right)\left[\text{basic}\right]$

(c) ${\mathbf{\text{MnO}}}_{\mathbf{4}}^{\mathbf{-}}\left(\text{aq}\right)\mathbf{ }\mathbf{+}\mathbf{ }{\mathbf{\text{H}}}_{\mathbf{2}}{\mathbf{\text{O}}}_{\mathbf{2}}\left(\text{aq}\right)\mathbf{\to }{\mathbf{\text{Mn}}}^{\mathbf{2}\mathbf{+}}\left(\text{aq}\right)\mathbf{ }\mathbf{+}{\mathbf{\text{O}}}_{\mathbf{2}}\left(\text{g}\right)\left[\text{acidic}\right]$

Consider the following general voltaic cell:

Identify the (a) anode, (b) cathode, (c) salt bridge, (d) electrode at which  leave the cell, (e) electrode with a positive charge, and electrode that gains mass as the cell operates (assuming that a metal plates out).

Consider the following voltaic cell:

(a) In which direction do electrons flow in the external circuit? 

(b) In which half-cell does reduction occur? 

(c) In which half-cell do electrons leave the cell? 

(d) At which electrode are electrons generated? 

(e) Which electrode is positively charged?

(f) Which electrode increases in mass during cell operation? 

(g) Suggest a solution for the anode electrolyte.

(h) Suggest a pair of ions for the salt bridge. 

(i) For which electrode could you use an inactive material? 

(j) In which direction do cations within the salt bridge move to maintain charge neutrality?

(k) Write balanced half-reactions and an overall cell reaction.

Consider the following voltaic cell

(a) In which direction do electrons flow in the external circuit? 

(b) In which half-cell does oxidation occur?

(c) In which half-cell do electrons enter the cell?

(d) At which electrode are electrons consumed?

(e) Which electrode is negatively charged? 

(f) Which electrode decreases in mass during cell operation?

(g) Suggest a solution for the cathode electrolyte.

(h) Suggest a pair of ions for the salt bridge.

(i) For which electrode could you use an inactive material?

(j) In which direction do anions within the salt bridge move to maintain charge neutrality? 

(k) Write balanced half-reactions and an overall cell reaction.

When a piece of metal A is placed in a solution containing ions of metal , metal plates out on the piece of A. 

(a) Which metal is being oxidized? 

(b) Which metal is being displaced? 

(c) Which metal would you use as the anode in a voltaic cell incorporating these two metals? 

(d) If bubbles of  ${\mathbf{\text{H}}}_{\mathbf{\text{2}}}$form when is placed in acid, will they form if A is placed in acid? Explain

A voltaic cell is constructed with an ${\mathbf{\text{S}}}_{\mathbf{\text{n}}}\mathbf{\text{/}}{{\mathbf{\text{S}}}_{\mathbf{\text{n}}}}^{\mathbf{\text{2 + }}}$half-cell and a ${\mathbf{\text{Z}}}_{\mathbf{\text{n}}}\mathbf{\text{/}}{{\mathbf{\text{Z}}}_{\mathbf{\text{n}}}}^{\mathbf{\text{2 + }}}$ half-cell. The zinc electrode is negative. 

(a) Write balanced half-reactions and the overall reaction. 

(b) Diagram the cell, labelling electrodes with their charges and showing the directions of electron flow in the circuit and of cation and anion flow in the salt bridge.

A voltaic cell is constructed with an ${\text{Ag/Ag}}^{\text{ + }}$half-cell and a ${\text{Pb/Pb}}^{\text{2 + }}$half-cell. The zinc electrode is negative. 

(a) Write balanced half-reactions and the overall reaction. 

(b) Diagram the cell, labeling electrodes with their charges and showing the directions of electron flow in the circuit and of cation and anion flow in the salt bridge.

A voltaic cell is constructed with an  ${\text{Fe/Fe}}^{\text{2 + }}$ half-cell and an  ${\text{Mn/Mn}}^{\text{2 + }}$ half-cell. The iron electrode is positive. 

(a) Write balanced half-reactions and the overall reaction. 

(b) Diagram the cell, labeling electrodes with their charges and showing the directions of electron flow in the circuit and of cation and anion flow in the salt bridge.

What purpose does the salt bridge serve in a voltaic cell, and how does it accomplish this purpose?

When a clean iron nail is placed in an aqueous solution of copper(II) sulfate, the nail becomes coated with a brownish black material. 

(a) What is the material coating the iron? 

(b) What are the oxidizing and reducing agents?

 (c) Can this reaction be made into a voltaic cell? 

(d) Write the balanced equation for the reaction. 

(e) Calculate E°cell for the process.