Electrochemical cells are crucial in understanding redox reactions and energy conversion. This document explores galvanic cells involving zinc and magnesium, detailing the roles of anodes and cathodes. It explains oxidation and reduction processes, electron flow, and ionic movement within the cells. The content is designed for chemistry students studying electrochemistry concepts and preparing for exams. Key topics include half-reactions, balanced ionic equations, and practical applications of galvanic cells.

Key Points

  • Explains the roles of zinc and magnesium in galvanic cells.
  • Details the oxidation and reduction processes in electrochemical reactions.
  • Covers electron flow direction and ionic movement in galvanic cells.
  • Includes balanced ionic equations for reactions involving zinc and magnesium.
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Unit 5 Part B ● MHR 65
Solutions to Practice Problems in
Chapter 10 Electrochemical Cells
Using Half-Reactions to Sketch a Galvanic Cell
(Student textbook page 641)
1. In a galvanic cell involving zinc and magnesium, which electrode will be the anode and
which will be the cathode?
What Is Required?
You are asked to identify the anode and cathode of a galvanic cell.
What Is Given?
You are given that one electrode is zinc and the second electrode is magnesium. You are also
given Relative Strengths of Oxidizing and Reducing Agents, Table 9.2 on page 587 of the
student textbook.
Plan Your Strategy
Act on Your Strategy
Identify the stronger reducing agent from
Table 9.2.
Between zinc and magnesium, magnesium is
the stronger reducing agent.
Since the stronger reducing agent is
always oxidized, and oxidation occurs at
the anode, the anode can be identified.
Since magnesium is the stronger reducing
agent, magnesium is oxidized and thus is the
anode in the galvanic cell.
Once the anode is identified, the other
electrode will be the cathode.
Given that the magnesium electrode is the
anode, the zinc electrode must be the cathode.
Check Your Solution
The stronger reducing agent, according to Table 9.2, is the anode, and the weaker reducing
agent is the cathode. The solution is correct.
66 MHR ● Chemistry 12 Solutions Manual 978-0-07-106042-4
2. Explain where the oxidation and the reduction are occurring in a galvanic cell involving zinc
and magnesium.
What Is Required?
You are to identify where the oxidation and the reduction are occurring in a galvanic cell.
What Is Given?
You are given that one electrode is zinc and the second electrode is magnesium. You are also
given Relative Strengths of Oxidizing and Reducing Agents, Table 9.2 on page 587 of the
student textbook.
Plan Your Strategy
Act on Your Strategy
Identify the stronger reducing agent from
Table 9.2.
Between zinc and magnesium, magnesium
is the stronger reducing agent.
Since the stronger reducing agent is always
oxidized, oxidation occurs at the anode.
Oxidation occurs at the magnesium
electrode.
The weaker reducing agent is always reduced
and reduction occurs at the cathode.
Reduction occurs at the zinc electrode.
Check Your Solution
Oxidation occurs at the electrode that is the stronger reducing agent, and reduction occurs at
the electrode that is the weaker reducing agent. The solution is correct.
Unit 5 Part B ● MHR 67
3. Draw a diagram of a galvanic cell involving zinc and magnesium, and indicate the direction
of electron flow.
What Is Required?
You are to draw a galvanic cell, labelling the anode, the cathode, and the direction of electron
flow.
What Is Given?
You are given the electrodes of magnesium and zinc for this galvanic cell.
Plan Your Strategy
Act on Your Strategy
Identify the pieces of the galvanic
cell.
The magnesium is the anode—the site of oxidation,
where magnesium ions flow into solution and
electrons leave the electrode and flow through the
voltmeter as they move to the zinc cathode. The zinc
is the cathode
—
the site of reduction, where zinc ions
flow onto the electrode as they pick up electrons.
Identify the direction of electron
flow.
In a galvanic cell, electrons flow from the anode to
the cathode, in t
his case, from the magnesium
electrode to the zinc electrode.
Identify the ion flow in the half-
cells.
Ions of magnesium will flow into the oxidation half-
reaction as the atoms of magnesium lose electrons.
Ions of zinc will flow onto the zinc electrode as
they
pick up electrons during the reduction.
Identify the ion flow in the salt
bridge.
Negative ions in the salt bridge will migrate towards
the oxidation half
-
reaction and positive charge builds
up in the cell. Positive ions will migrate towards the
red
uction half-cell as positive charge is removed
from the half
-
cell, leaving a net negative charge in
this half
-
cell that will attract the positive ions in the
salt bridge.
Sketch the apparatus, including the
beakers, electrodes, conducting
wires, voltmeter, salt bridge, and
electron flow.
Check Your Solution
Electrons flow from the site of oxidation at the magnesium anode to the site of reduction at
the zinc cathode. The drawing is correct.
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FAQs

What is the role of zinc in a galvanic cell?
In a galvanic cell, zinc acts as the cathode where reduction occurs. Zinc ions in solution gain electrons to form solid zinc, facilitating the flow of electrons from the anode. This process is crucial for generating electrical energy in the cell. The overall reaction highlights the importance of zinc in energy conversion.

How does oxidation occur in a galvanic cell?
Oxidation in a galvanic cell occurs at the anode, where a stronger reducing agent loses electrons. For example, in a cell with zinc and magnesium, magnesium is oxidized, releasing electrons into the circuit. This electron flow is essential for the functioning of the galvanic cell, driving the reduction process at the cathode.

What is the significance of electron flow in galvanic cells?
Electron flow in galvanic cells is critical for generating electrical energy. Electrons move from the anode, where oxidation occurs, to the cathode, where reduction takes place. This flow not only powers external circuits but also drives the chemical reactions within the cell, making it a fundamental concept in electrochemistry.

What balanced ionic equation represents the reaction in a galvanic cell with zinc and magnesium?
The balanced ionic equation for the reaction in a galvanic cell involving zinc and magnesium is Mg(s) + Zn2+(aq) → Zn(s) + Mg2+(aq). This equation illustrates the transfer of electrons from magnesium to zinc ions, highlighting the oxidation of magnesium and the reduction of zinc. Understanding this equation is key for students studying electrochemical reactions.

What are the main components of a galvanic cell?
A galvanic cell consists of two electrodes, an anode and a cathode, immersed in electrolyte solutions. The anode is where oxidation occurs, while the cathode is where reduction takes place. Additionally, a salt bridge connects the two half-cells, allowing for ionic movement to maintain charge balance. These components work together to facilitate the flow of electrons and generate electrical energy.