Galvanic and Electrolytic Cells

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Questions and Answers

In a galvanic cell, if the individual electrode reactions are not written in the correct direction, what is the most likely consequence?

  • The overall cell reaction will be thermodynamically unfavorable. (correct)
  • The measured cell voltage will be higher than expected.
  • The overall cell reaction will proceed spontaneously, but at a slower rate.
  • There will be no impact on the cell reaction or voltage.

Which of the following describes the primary function of a salt bridge in a galvanic cell?

  • To provide a surface for the oxidation and reduction reactions to occur.
  • To maintain electrical neutrality in the half-cells, allowing the reaction to proceed. (correct)
  • To physically separate the two half-cells, preventing mixing of the electrolytes.
  • To facilitate direct electron transfer between the two half-cells.

In standard cell notation, what does a double vertical line (||) represent?

  • Direct contact between two solutions.
  • A salt bridge connecting two half-cells. (correct)
  • Phase boundary between solid electrode and aqueous solution.
  • The flow of electrons in the external circuit.

Given the cell notation $Zn(s) | ZnSO_4(aq) || CuSO_4(aq) | Cu(s)$, which half-cell reaction occurs at the anode?

<p>$Zn(s) \rightarrow Zn^{2+}(aq) + 2e^-$ (B)</p> Signup and view all the answers

Consider a galvanic cell constructed with a zinc electrode in zinc sulfate solution and a copper electrode in copper sulfate solution. If the concentration of $Cu^{2+}$ ions is increased, what effect will this have on the cell potential?

<p>The cell potential will increase. (D)</p> Signup and view all the answers

A galvanic cell is represented as $Fe | Fe^{2+} || Pb^{2+} | Pb$. Which of the following statements accurately describes the electron flow in this cell?

<p>Electrons flow from the iron electrode to the lead electrode. (A)</p> Signup and view all the answers

Which equation is used to calculate the standard cell potential ($E_{cell}$) in a galvanic cell, given the standard reduction potentials of the cathode ($E_{cathode}$) and anode ($E_{anode}$)?

<p>$E_{cell} = E_{cathode} - E_{anode}$ (B)</p> Signup and view all the answers

Consider a galvanic cell with a standard cell potential of 1.10 V. If the reaction at the anode is $Zn(s) \rightarrow Zn^{2+}(aq) + 2e^-$ and the standard reduction potential for $Zn^{2+}$ is -0.76 V, what is the standard reduction potential for the cathode reaction, assuming it involves copper?

<p>0.34 V (C)</p> Signup and view all the answers

What is the standard reference point for measuring electrode potentials, to which all other electrode potentials are compared?

<p>Standard Hydrogen Electrode (C)</p> Signup and view all the answers

If the standard potential of a $Zn | Zn^{2+}$ electrode is given as 0.76 V, and a galvanic cell is set up as $Zn | Zn^{2+}(a=1) || H^+(a=1) | H_2(P=1 atm) (pt)$, what does this potential signify?

<p>The electromotive force (e.m.f) of the cell is 0.76 V. (D)</p> Signup and view all the answers

In the context of electrolytic cells, which of the following best describes a nonspontaneous reaction?

<p>A reaction that requires energy input to proceed and does not occur naturally. (D)</p> Signup and view all the answers

What distinguishes an electrolytic cell from a galvanic cell in terms of energy conversion?

<p>Electrolytic cells convert electrical energy into chemical energy, while galvanic cells convert chemical energy into electrical energy. (A)</p> Signup and view all the answers

In an electrolytic cell, to which pole of an external direct current (d.c) power supply is the cathode connected, and what type of reaction occurs there?

<p>Negative pole; reduction reaction (A)</p> Signup and view all the answers

During the electrolysis of an aqueous solution, what determines the movement of ions within the solution?

<p>Positive ions (cations) migrate toward the cathode, while negative ions (anions) migrate toward the anode. (C)</p> Signup and view all the answers

During electrolysis, if the solution temperature increases due to the electrical energy converting to heat, what is the primary cause of this heat generation?

<p>The internal cell resistance opposes the flow of current. (A)</p> Signup and view all the answers

Compared to galvanic cells, what is a key difference in how ions are discharged on the electrodes in electrolytic cells?

<p>In electrolytic cells, ions are discharged at both electrodes, whereas in galvanic cells, ions are consumed at one electrode and discharged at the other. (B)</p> Signup and view all the answers

If a metal X has a higher tendency to lose electrons compared to metal Y, how will their positions typically appear in the electromotive series (EMS)?

<p>Metal X will be above metal Y in the EMS. (A)</p> Signup and view all the answers

Why is the hydrogen electrode assigned an arbitrary zero voltage in electrochemistry?

<p>The absolute value of a single electrode potential cannot be measured without a reference. (B)</p> Signup and view all the answers

What is the significance of the electromotive series (EMS) in predicting the feasibility of a redox reaction?

<p>The EMS helps determine if a reaction will occur spontaneously. (C)</p> Signup and view all the answers

How is the 'difference in potential' useful when single electrode potentials cannot be measured directly?

<p>It makes it possible to compare the relative tendencies of different electrodes to undergo reduction or oxidation. (B)</p> Signup and view all the answers

Which of the following is a practical application of electrolytic cells?

<p>Electroplating a metal object with a thin layer of another metal. (B)</p> Signup and view all the answers

Which of the following is a practical application of galvanic cells?

<p>Powering portable electronic devices. (B)</p> Signup and view all the answers

How does the spontaneity of a reaction differ between galvanic and electrolytic cells?

<p>Galvanic cells involve spontaneous reactions, whereas electrolytic cells involve non-spontaneous reactions. (B)</p> Signup and view all the answers

Which device is used to measure the amount of electricity produced by a Galvanic cell?

<p>Coulometer (C)</p> Signup and view all the answers

Flashcards

What is a galvanic cell?

A device that converts chemical energy into electrical energy through spontaneous redox reactions.

Electrode Reaction Direction

In a galvanic cell, individual electrode reactions are written in the direction of the overall cell reaction.

What is the Anode?

The electrode where oxidation (loss of electrons) occurs, designated as the negative terminal in a galvanic cell.

What is the Cathode?

The electrode where reduction (gain of electrons) occurs, designated as the positive terminal in a galvanic cell.

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What does a single vertical line (|) mean in cell notation?

Vertical line (|) denotes separation of phases (e.g., electrode and solution).

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What do double vertical lines (||) mean in cell notation?

Double vertical lines (||) represent a salt bridge separating two half-cells.

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What is Ecell?

It is the difference between the reduction potentials of the cathode and anode.

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What is the Electromotive series (e.m.s)?

A list of chemical species organized by their tendency to gain or lose electrons

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What is the standard hydrogen electrode (SHE)?

The reference point (0 volts) for measuring all other electrode potentials.

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What is a Standard electrode potential?

Electrode potential measured under standard conditions (1 M, 1 atm, 25°C) relative to the standard hydrogen electrode.

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What is an Electrolytic cell?

A cell that uses electrical energy to drive non-spontaneous chemical reactions.

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What is the energy conversion in electrolytic cells?

Converts Electrical Energy into Chemical Energy

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What is the Anode in an Electrolytic Cell?

The electrode connected to the positive pole of a DC power supply where oxidation occurs.

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Cathode in an Electrolytic cell

Electrolytic cathode is the -ve electrode, where reduction occurs.

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What happens during electrolysis?

Migration of ions in solution and flow of electrons through connecting wires.

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Ion Movement in Electrolysis

Positive ions migrate to the cathode; negative ions migrate to the anode.

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What is a galvanic cell?

A cell that produces electrical energy using spontaneous chemical reactions.

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What is an electrolytic cell?

A cell that drives a chemical reaction using electrical energy.

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Energy conversion in galvanic cell.

Chemical to electrical energy.

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What is the anode in a galvanic cell?

Electrode where oxidation occurs and it has a negative sign.

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What is the cathode in a galvanic cell.

Electrode where reduction occurs and has a +ve sign.

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Ions on electrodes in galvanic cells

Discharged at the cathode, ions get reduced.

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Electron flow direction in galvanic cell

Anode to cathode.

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Applications of electrolytic cells.

Purification and electroplating processes.

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Applications of galvanic cells.

Batteries, etc.

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Study Notes

  • Galvanic cells and electrolytic cells both involve electrochemical reactions, but differ in their spontaneity and energy conversion

Galvanic Cells

  • Overall cell reactions must have individual electrode reactions written in the correct direction
  • The left-hand electrode is the negative electrode (anode) where oxidation (loss of electrons) occurs
  • The right-hand electrode is the positive electrode (cathode) where reduction (gain of electrons) takes place
  • Vertical lines (|) separate liquids from solids in cell notation
  • Double vertical lines (||) indicate a salt bridge
  • Commas (,) are placed between two electrolytes in the same solution
  • Dotted lines are for two solutions in direct contact at their interface
  • The cell potential (Ecell) is the difference between the cathode and anode potentials: Ecell = Ecathode - Eanode
  • Ecathode is the reduction potential of the cathode half-cell where reduction occurs
  • Eanode is the oxidation potential of the anode half-cell where oxidation occurs
  • The electromotive series (e.m.s) lists chemical species by their tendency to gain or lose electrons (undergo reduction or oxidation)
  • Electromotive series values are measured in volts relative to the hydrogen electrode, which is the standard with an arbitrarily assigned zero voltage
  • Evaluating electrode potentials involves using the hydrogen electrode (H2) in its standard state as the reference, enabling measurement of other electrode potentials against it
  • The potential of the H2 electrode in its standard form is assigned a value of zero
  • Standard potential of Zn | Zn++ electrode is 0.76V, meaning the e.m.f of the galvanic cell Zn | Zn++ (a=1) || H+ (a=1)| H2(P=1atm) (pt) is 0.76V

Electrolytic Cells

  • Electrolytic cells are electrochemical reactors, where thermodynamically nonspontaneous reactions are made to occur by providing energy in the form of electrical energy
  • Electrical energy is converted into chemical energy in a nonspontaneous manner
  • Electrolytic cells consist of two electrodes in a container with an electrolyte
  • One electrode is connected to the negative pole and the other to the positive pole of an external direct current (d.c.) power supply
  • The anode is connected to the positive pole of the power supply
  • The cathode is connected to the negative pole of the power supply
  • Oxidation occurs at the anode
  • Reduction takes place at the cathode
  • During electrolysis, electrical current is carried by ion migration in solution and electron flow through the connecting wires outside the solution
  • Positive ions migrate toward the negative electrode (cathode), and negative ions migrate toward the positive electrode (anode)
  • The solution temperature increases due to the conversion of part of the electrical energy into heat, Q (Q = I2R), owing to internal cell resistance R
  • Heat generation in the solution may adversely affect cell performance

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