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Name:
………………………….
Class:
Grade 9
Subject:
Electrochemistry.
Objective: To identify galvanic cell.
Worksheet (4.2)
1. Consider the Cu – Ag Galvanic cell (Cu is more reactive than Ag)
a. List the materials needed to construct the Cu-Ag Galvanic cell
b. Describe, briefly, the procedure to construct the required Galvanic cell.
c. Sketch and label the Galvanic cell.
d. Write the half-reactions that occur at the electrodes.
e. Write the overall (cell) reaction.
f. Give a written representation of this Galvanic cell.
2. The schematic drawing given below
describes Al-Zn Galvanic cell.
Beaker A contains Al3+
Beaker B contains Zn2+
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
Indicate the anode and cathode.
Write the half reactions taking place at each electrode.
Deduce the over all reaction.
Identify the oxidant and reductant.
Label the drawing.
Describe briefly, the procedure to construct the required Galvanic cell.
Give a written representation for this Galvanic cell.
How can you explain that this Al-Zn is a Galvanic cell?
Give two examples on Galvanic cell from our daily life.
Explain the difference in potential of the following four pairs of metals.
 Zn –Ag Galvanic cell ( potential difference = 1.56 V)
 Cu –Ag Galvanic cell ( potential difference = 0.46 V)
 Cu –Zn Galvanic cell ( potential difference = 1.1 V)
 Mg –Cu Galvanic cell ( potential difference = 2.7 V)
3. Silver-Copper electrochemical cell:
We try to construct a cell as the one indicated in
the set-up.
1. Here are different solutions copper (II) nitrate,
aluminum nitrate, iron (II) nitrate, silver nitrate.
In what solution do we dip each of the electrodes?
2. Identify the electrodes of the cell. Justify.
3. Write the half reactions taking place at each
electrode as well as the overall cell reaction.
4. Identify the oxidizing and reducing agents.
5. Describe the steps in order to construct this cell.
Worksheet in Chemistry / Prepared by: T. Wissam Abdallah
4. Consider the Cu/Mg Galvanic cell.
-Beaker (A): stands for half-cell.
-Magnesium ribbon (Mg)
-( Mg2+ + 2NO3- ) solution
-Beaker (B): stands for half-cell.
-Copper strip (Cu)
-( Cu2+ + 2NO3- ) solution
-Salt bridge, connecting the two half-cells.
a- Explain why the lamp lights when the external circuit is complete.
b- How does the quantity of Mg2+ ions vary in beaker (A)? Justify.
c- The blue color of the solution in beaker (B) gradually fades. Explain
d- Deduce what originates electric energy.
e- What happens if we remove the salt bridge? Deduce the role of salt bridge.
g- Indicate the anode and the cathode? Justify.
5. Required to realize the following cell: Mg/ Mg2+ bridge Cu2+/ Cu
a. Describe briefly how to construct this cell.
b. Sketch and label this cell.
c. Write the half-reactions occurring at electrodes.
d. Deduce the over-all equation.
e. Deduce the origin of electrical energy.
6. Consider the Galvanic cell: Cr / Cr3+ // Ag+ / Ag
a. Identify oxidized and reduced substances
b. Identify oxidant and reductant.
c. Write down half reactions taking place at anode and cathode.
d. Write down the over-all reaction.
e. Describe, briefly, the procedure to construct the above Galvanic cell.
f. Sketch and label the above Galvanic cell.
7.
Consider an electrochemical cell where the reaction of the functioning is translated by
the following unbalanced equation.
Cr + Cu2+ → Cr3+ + Cu
a.
b.
c.
d.
e.
f.
g.
h.
Identify the nature of each of the electrodes. Justify.
Schematize and label the cell.
Write the half-reactions taking place at anode and cathode respectively.
Write the over-all equation of the reaction.
Identify the oxidant and reductant respectively. Justify.
Give a written representation of the above cell.
A deposit is formed on one of the metallic plates. Identify this deposit.
During the function of this cell one electrode increases by mass (m).
i.
Which electrode is this?
ii. How does the mass of the other electrode vary?
i. The charge carriers migrate in solution across the salt bridge, the positive ions
towards the cathode and the negative ions towards the anode. The solutions remain
electrically neutral.
i.
Indicate the direction of the migration of the different charge carriers.
ii. Deduce the role of the salt bridge.
Worksheet in Chemistry / Prepared by: T. Wissam Abdallah
8. Consider an electrochemical cell where the reaction of the functioning is translated by
the following unbalanced equation.
Zn + Au3+ → Zn2+ + Au
a.
b.
c.
d.
e.
f.
g.
h.
Identify the nature of each of the electrodes. Justify.
Schematize and label the cell.
Write the half-reactions taking place at anode and cathode respectively.
Write the over-all equation of the reaction.
Identify the oxidant and reductant respectively. Justify.
Give a written representation of the above cell.
A deposit is formed on one of the metallic plates. Identify this deposit.
During the function of this cell one electrode increases by mass (m).
 Which electrode is this?
 How does the mass of the other electrode vary?
i. The charge carriers migrate in solution across the salt bridge, the positive ions
towards the cathode and the negative ions towards the anode. The solutions remain
electrically neutral.
 Indicate the direction of the migration of the different charge carriers.
 Deduce the role of the salt bridge.
9. A device capable to convert chemical energy to electric energy is called Galvanic cell.
When a strip of silver is dipped into a beaker containing copper (II) sulfate solution, an
oxidation – reduction reaction occurs. The equation of the reaction is given as :
2Ag + Cu2+ →
2Ag+ + Cu
It is required to construct the Galvanic cell (G), which when set to function its overall
(cell) reaction will be the reaction given above.
Following materials are available :
Zinc, copper, magnesium and silver strips
Solution containing copper (II) (Cu2+ ) ions
Solution containing magnesium (Mg2+) ions
Solution containing zinc (Zn2+) ions
Solution containing silver (Ag+) ions
2 beakers
U – shaped salt bridge KNO3
U- shaped copper wire
connecting wires and alligator clips
a voltmeter, DC power supply.
a. List from the available materials those that are essential components of the Galvanic
cell (G) to be constructed.
b. Describe how to construct the Galvanic cell (G).
c. Sketch and label the constructed Galvanic cell (G), which is set to function and show
the direction of the electron flow.
d. Specify the direction of the movement of the ions in the salt bridge. Justify.
e. Write the half - reactions taking place at each electrode.
f. Identify the reducing and oxidizing agents.
g. What form of energy is obtained due to the above reaction?
h. How does the quantity of silver ions ( Ag+) vary? Justify.
i. The color of blue solution fades gradually with time. Explain.
Worksheet in Chemistry / Prepared by: T. Wissam Abdallah
10. Consider the following setups that are constructed in order to study Galvanic cells.
a. Give the name of each of the 3 numbered components in setup (A)&(B).
b. The voltmeter in the setup (D) indicates zero volt reading. Explain.
c. Referring to setup (C) :
a. Indicate which of the following representations corresponds to the Galvanic
cell of the setup ( C ):
2+
 Mg / Mg
salt bridge Cu2+ / Cu
2+
 Mg / Mg
salt bridge Cu / Cu2+
2+
2+
 Cu / Cu salt bridge Mg / Mg
b. Specify the anode and the cathode for this Galvanic cell.
c. Write the equation of the half-reactions taking place at the anode and
cathode. Deduce the overall (cell ) reaction that takes place while the
Galvanic cell is functioning.
d. Setup ( C) is considered as a Galvanic cell. Justify.
e. Indicate the direction of anions and cations in salt bridge. Justify.
Worksheet in Chemistry / Prepared by: T. Wissam Abdallah
11. Consider the following setups that are constructed in order to study Galvanic cells.
a. Give the name of each of the 3 numbered components in setup (A)&(B).
b. The voltmeter in the setup (D) indicates zero volt reading. Explain.
c. Referring to setup (C) :
d.
f. Indicate which of the following representations corresponds to the Galvanic
cell of the setup ( C ):
2+
 Zn / Zn
salt bridge Ag / Ag+
2+
 Zn / Zn
salt bridge Ag+ / Ag
+
2+
 Ag / Ag salt bridge Zn / Zn
g. Specify the anode and the cathode for this Galvanic cell.
h. Write the equation of the half-reactions taking place at the anode and
cathode. Deduce the overall (cell ) reaction that takes place while the
Galvanic cell is functioning.
i. Setup ( C) is considered as a Galvanic cell. Justify.
j. Indicate the direction of anions and cations in salt bridge. Justify.
Worksheet in Chemistry / Prepared by: T. Wissam Abdallah