Deck 15: Fundamentals of Electrochemistry

Question 1

For the line notation below,which is NOT true? Fe(s)| Fe²⁺ (aq,A = 1)|| Cu²⁺ (aq,A = 1)| Cu (s)

A)Fe is the anode.
B)|| represents the salt bridge.
C)Cu is the anode.
D)1 M Cu²⁺ is the electrolyte concentration and species for the copper electrode.
E)1 M Fe²⁺ is the electrolyte concentration and species for the iron electrode.

Answer 1

Cu is the anode.

Question 2

Calculate the equilibrium constant for the reaction between Sn metal and Zn²⁺ solution. Sn + Zn²⁺ ⇋ Sn²⁺ + Zn
Sn²⁺ + 2 e⁻ → Sn (s)E° = −0.141 V
Zn²⁺ + 2 e⁻ → Zn (s)E° = −0.762 V

A)9)86 × 10²⁰
B)1)21 × 10⁻²¹
C)3)37 × 10³⁰
D)3)18 × 10⁻¹¹
E)1)84 × 10¹⁵

Answer 2

1)21 × 10⁻²¹

Question 3

Calculate E^°' for the half-cell below. O₂ + 4 H⁺ + 4 e⁻ ⇋ 2 H₂O E° = 1.229 V

A)1.643 V
B)0.815 V
C)0.307 V
D)1.229 V
E)0.711 V

Answer 3

0.815 V

Question 4

For the silver half-reaction,Ag⁺ + 1 e^- → Ag (s),when the concentration of silver cation is increased,the reduction potential:

A)becomes more positive.
B)becomes more negative.
C)remains constant.
D)increases or decreases depending on the voltage of the other half-reaction.
E)increases or decreases depending on the temperature.

Question 5

Calculate E^o and K for the cell composed of a bromate/bromide half-cell and a chlorate/chlorine dioxide half-cell. + 2 H⁺ + e⁻ ⇋ ClO₂ + H₂O E° = 1.130 V + 3 H₂O + 6 e⁻ ⇋ Br⁻ + 6 OH⁻ E° = 0.613 V

Question 6

For the cell diagram below write out and balance the reaction that occurs in the cell.
Pt|HOCl (aq,1 M),HClO₂ (aq,1 M),H⁺ (aq,1 M)|| (aq,1 M),H⁺ (aq,1 M)| MnO₂ (s)|Pt

Question 7

All of the following are true for the measurement of standard reduction potentials,except:
I standard conditions for reduction potentials is 25 ^oC and A = 1 for all aqueous and gaseous species.
II reduction potentials are measured relative to the standard hydrogen electrode (S.H.E. ).
III standard reduction potentials are measured while connected to the negative electrode of the potentiometer.
IV the E^° for the S.H.E.is defined as 0 volts.

A)I and IV
B)I and III
C)I only
D)III only
E)II and IV

Question 8

Calculate the standard potential when the two half-cells below are connected via a salt bridge and potentiometer.Which species are the reducing agent and oxidizing agent? + 2 H⁺ + 2 e^- ⇋ + H₂O E° = 1.589 V
Mg(OH)₂ (s)+ 2 e^- ⇋ Mg (s)+ 2 OH^- E° = -2.690 V

Question 9

A bromide probe is constructed from a saturated silver bromide half-cell and a Ni²⁺/Ni half-cell.If the measured potential is 0.952 V and [Ni²⁺] = 1 M,what is the bromide concentration?
AgBr (s)+ e⁻ ⇋ Ag(s)+ Br⁻ E^° = 0.071 V
Ni²⁺ + 2 e⁻ ⇋ Ni (s)E^° = −0.714 V

Question 10

For the reaction below,the oxidizing agent is____________________ and it____________________ electrons,and the reducing agent is____________________ and it____________________ electrons. 8 H⁺ + + 5 Cu⁺ ⇋ Mn²⁺ + 5 Cu²⁺ + 4 H₂O

A)
;gains 5;Cu⁺;loses 1
B)H⁺;loses 1;Cu⁺;gains 1
C)H⁺;gains 1;

;loses 5
D)Cu⁺;loses 1;

;gains 1
E)Cu⁺;loses 1;H⁺;gains 1

Question 11

A galvanic cell is at equilibrium when:

A)E_cell is a constant value.
B)cell resistance is very low.
C)E_cell = 0 V.
D)E_cell fluctuates between $\pm$ E°_cell.
E)cell resistance is infinitely large.

Question 12

Which is true when electrochemical cells are used as chemical probes?
I.All concentrations in the half-cells must be known except for the analyte of interest.
II. The analyte concentration is calculated from the equilibrium cell potential.
III. Equilibrium between the half-cells is established.
IV. Equilibrium within each half-cell is established and is assumed to remain at equilibrium.
V. Half-cells other than the S.H.E.can be used to determine pH.

A)II,III,and IV
B)I,IV,and V
C)I and II
D)III,IV,and V
E)I,II,and V

Question 13

Which is NOT correct for when the silver and vanadium half-cells are connected via a salt bridge and a potentiometer?
Ag⁺ + 1 e^- → Ag (s)E° = 0.7993 V
V²⁺ + 2 e^- → V (s)E° = −1.125 V
I Ag⁺ is reduced.
II V is oxidized.
III E^o_cell = 1.924 V
IV V²⁺ is reduced.
V Ag is oxidized.

A)I and II
B)III,IV,and V
C)I,II,and III
D)III only
E)IV and V

Question 14

E^o' is defined as:

A)the formal half-cell potential for compounds that are neither acids nor bases.
B)the formal half-cell potential at 20 $\degree$ C.
C)the formal half-cell potential at pH 7.
D)the inverse of E°.
E)None of these answers is the definition of E°'.

Question 15

The half-cells below are connected via a salt-bridge and potentiometer.What is the voltage read by the potentiometer when A_Ag⁺ = 2.00 and A_V²⁺ = 1.50? Ag⁺ + 1 e⁻ → Ag (s)E^o = 0.7993 V
V²⁺ + 2 e⁻ → V (s)E^o = −1.125 V

A)1)912 V
B)−0.326 V
C)−0.313 V
D)1)937 V
E)1)924 V

Question 16

Which of the following is NOT true for galvanic cells?

A)Galvanic cells are spontaneous.
B)Oxidation occurs at the anode and reduction occurs at the cathode.
C)Electrons move toward more negative electrical potential.
D)Galvanic cells are composed of two half-cells connected by salt bridge.
E)The salt bridge maintains electroneutrality throughout the cell.

Question 17

A cell is constructed according to the cell diagram below.If the measured potential is 1.00 V,what is the pH of the dichromate cell? Fe|Fe²⁺ (aq,1M)|| (aq 1 M),Cr²⁺ (aq,1 M),H⁺ (aq,x M)|Pt + 14 H⁺ + 6 e⁻ ⇋ 2 Cr³⁺ + 7 H₂O E° = 1.36 V
Fe²⁺ + 2 e⁻ ⇋ Fe (s)____________________ E° = −0.44 V

A)1)931
B)5)797
C)12.162
D)6)081
E)4)054

Question 18

Which relationship is NOT correctly defined?

A)Work = E. q
B)( $\Delta$ G = -n · F · E)
C)
D)P = E . I
E)q = n .N .F

Question 19

Calculate the potential for the half-cell below for [ ] = 0.100 M,[ ] = 0.500 M and the pH = 10.50.
2 + 3 H₂O + 4 e⁻ ⇋ + 6 OH^- E° = −0.566 V

Question 20

A galvanic cell with a large equilibrium constant has a____________________ cell potential.

A)negative
B)constant
C)zero voltage
D)positive
E)variable