F.Sc. Part 1 Chemistry.Ch.10.Test (Malik Xufyan)

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Chapter # Topic Page #
Basic concepts – Unsolved paper1
2
3
4
5
6
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8
9
10
11
5
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16
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36
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45
46
54
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64
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73
74
83
84
93
94
103
104
Experimental Techniques – Solved Paper
Gases – Unsolved Paper
Gases – Solved Paper
Liquid – Unsolved Paper
Liquid – Solved Paper
Atomic Structure – Unsolved Paper
Atomic Structure – Solved Paper
Chemical Bonding –Unsolved Paper
Chemical Bonding – Solved Paper
Thermochemistry – Unsolved Paper
Thermochemistry – Solved Paper
Chemical Equilibrium – Unsolved Paper
Chemical Equilibrium – Solved Paper
Solu on – Unsolved Paper
Solu on – Solved Paper
Electrochemistry – Unsolved Paper
Electrochemistry – Solved Paper
Chemical Kine cs – Unsolved Paper
Chemical Kine cs – Solved Paper
Basic concepts – Solved Paper
Experimental techniques – Unsolved Paper
INDEX

Chapter#10:Electrochemistry Malik Chemistry
Jhang Institute for Advanced94
Name : CH # Electrochemistry Class 11th
Chemistry Test # 10 , CH # 10 (Complete) Marks : 85
Time : 2 & Half Hour Objective & Subjective JIAS Test System
Section-I= Objective
1. Choose Correct Answer 17x1=17
Sr # Statement A B C D
1. Oxidation state of carbon atoms in diamond and
graphite are
+2,+4 -4,+4 +4,+2 Zero
2. Which of the following agents is the most oxidizing O3
H2
O2
KMnO4
K2
Cr2
O7
3. Dissociation of an electrolyte in water into
negative and positive ions is called
Ionization Decomposition Electrolysis Hydrolysis
4. The process in which chemical change occur on
passing electricity is called
Ionization Electrolysis Neutralization Hydrolysis
5. Molten sodium chloride conducts electricity due
to presence of
Free electrons Free molecules Free ions Free atoms of Na
and Cl
6 In electroplating ,the article to be electroplated
serve as
Cathode Anode Electrolyte Conductor
7. In electrolysis oxidation takes place at Both the electrodes Anode Cathode In the solution
8. Strongest reducing agent is K Mg Al I
9. In a spoon of copper metals placed in a solution of
ferrous sulphate then
Cu will precipitate Cu and Fe will
precipitate
Iron will precipitate No reaction will
take place
10. Which of the following metal is most readily
corroded in moist air
Copper Silver Iron Nickel
11. Which is not true for a standard hydrogen
electrode
The hydrogen ion
concentration is
1M
Temperature is 25 o
C Pressure of hydrogen
is 1 atm
It contains a
metallic conductor
which does not
absorb hydrogen
12. The reaction is spontaneous if the cell potential is Positive Zero Negative Infinite
13. Which of the following gains electrons more easily Na+
Al+3
Zn +2
H+
14. When a lead storage battery is charged ,then PbO2
Dissolves Sulphuric acid is
regenerated
The lead electrode
becomes coated with
lead sulphate
The amount of acid
decreases
15. An example of a simple fuel cell is Lead storage
battery
Daniel cell H2
–O2
Cell Silver oxide cell
16. A catalyst is a substance which Increase the
equilibrium
concentration of
the product
Changes the
equilibrium constant
of the reaction
Shortens the time to
reach equilibrium
Supplies energy to
the reaction
17. More electronegative elements have Negative reduction
potential
Positive reduction
potential
Tendancy to lose
electrons
Positive oxidation
Potential

Jhang Institute for Advanced Studeies 95
Section-Il: Short Questions
2. Attempt any eight questions 8 x 2= 16
i. Explain the term oxidation number with examples.
ii. Calculate the oxidation number of Cr in the following
compounds 1)CrCl3
2)k2
CrO4
3)CrO 3
iii. Explain the differences between ionization and electroly-
sis?
iv. Explain the differences between conduction through
metals and molten electrolytes?
v. Impure Cu can be purified by an electrolytic process?
vi. Describe galvanic cell.
vii. Write function of salt bridge?
viii. How salt bridge maintains the electrical neutrality?
ix. Differentiate between single electrode potential and stan-
dard electrode potential?
x. Standard oxidation potential of Zn is 0.76 volts and re-
duction potential -0.76 volts?
xi. Write some applications of electrochemical series?
xii. How do u justify that lead accumulator is chargeable bat-
tery?
3. Attempt only eight questions 8 X 2 = 16
i. Write construction of SHE?
ii. Differentiate between oxidizing agent and reducing
agent?
iii. Differentiate between primary and secondary cells?
iv. What is emf and how we calculate the emf of a galvanic
cell?
v. Why alkali metals react vigorously with water while coin-
age metals do not react?
vi. How ionized aluminium is prepared?
vii. What is the difference between a cell and a battery?
viii. What is emf of a cell?
ix. Give conditions of electric conduction through electro-
lytes?
x. Define electrochemistry and describe electrolytic cell?
xi. Difference between down’s and nelson cell?
xii. What is electroplating?
4. Attempt any 6 questions 6 x 2 = 12
i. How electrode potential is measured?
ii. Define electrochemical series?
iii. Na and K can disperse hydrogen from acids but pt, pd, Cu
cannot?
iv. Lead accumulator has desirable characteristics?
v. What is alkaline battery ?write reactions
vi. Define nickel cadmium cell?
vii. Draw a diagram of hydrogen –oxygen fuel cell?
viii. What are uses of fuel cell?
Section-lIl: Long Questions.
Attempt any three questions.8 x 3 = 24
5) a) Write note on application of electrochemi-
cal series?
b) Write a detailed note on fuel cell?
6) a)Describe the construction and working of
standard hydrogen potential?
b) Describe general rules for balancing a redox
equation by ion-electron method also balance
the following equation.
MnO4
- +C2
O4
-2
→ Mn+2
+CO2
7) a)Describe the general rules for balancing a
redox equation by oxidation number method
,also balance following equation .
FeSO4
+K2
Cr2
O7
+H2
SO4
→K2
SO4
+H2
O +Cr2
(-
SO4
)3
+ Fe2
(SO4
)3
b) Write a note on voltaic or galvanic cell.
8) a) Explain lead accumulator battery with the help of
discharging and recharging.
b) Write note on Nikel Cadmium battery and Al-
kaline battery?
9) a) Write working, construction and diagram of electro-
lytic cell
b) Describe electrolysis process of industrial im-
portance.

Section-l: Short Questions
2. Attempt any EIGHT short Questions. 8 x 2= 16
i. Explain the term oxidation number with examples
It is the apparent charge on an atom of an element in a molecule or ion.
It may be positive or negative or zero.
For example: oxidation number of Mn in KMnO4
is.
Oxidation number of K = +1
Oxidation number of O = -2
Let oxidation number of Mn = x
Thus for KMnO4
+1 + x +4(-2) = 0
x – 7 = 0
x = +7
ii. Calculate the oxidation number of Cr in the following compounds 1)CrCl3
2)K2
CrO4
3)CrO 3
CrCl3
Oxidation number of Cl = -1
Oxidation number of Cr = x
Oxidation number of Cr can be
Calculated as
For CrCl3
x + 3(-1) = 0
x – 3 = 0
or x = 3
K2
CrO4
Oxidation number of K = +1
Thus
For K2
CrO4
2(+1) + x + 4 (-2) = 0
x – 6 = 0
or x = +6
CrO3
Thus
For CrO3
x + 3(-2) = 0
x – 6 = 0
or x = +6
iii. Explain the differences between ionization and electrolysis?
Ionization Electrolysis
1 The process in which ionic compounds
when fused or dissolved in water split up
into charged particles called ions
1 It is the decomposition of ionic compounds
by the passage of electric current.
2 Electrodes and electricity are not needed. 2 Electrodes and electricity are required.

3 Its spontaneous process 3 Its non spontaneous process
Examples:
NaCl (s)
H2O
Na+
(aq)
+ Cl-
(aq)
Examples:
Nelson’s cell and Down’s cell
iv. Explain the differences between conduction through metals and molten electrolytes ?
Conduction through metals Conduction through molten electrolyte
1 Electrical conduction takes place due to
free electrons.
1 Electrical conduction takes place due to ions.
3 In this case, conductance decreases with
the increase in temperature.
3 In this case, conductance increases with the
increase in temperature.
4 No chemical reaction occurs during
conduction.
4 Chemical reaction occurs takes place during
conduction.
5 Example: all metals are conductors e.g.
Fe, Pb etc.
5 Example: molten state e.g. NaCl (l)
or their
aqueous solution.
v. Impure Cu can be purified by an electrolytic process?
Impure Cu can be made pure in an electrolytic cell. Thick sheets of impure Cu are made anode, while
thin sheets of pure Cu are made cathode in the cell. These sheets are placed in an electrolytic solution
of CuSO4
.
When current is passed through the cell, Cu from anode is oxidized to Cu2+
ions, which go into the
solution. From the solution, Cu2+
ions are reduced to metallic Cu and deposits as pure Cu on cathode.
In this way, impure sheets of Cu(anode) become thin, while pure sheets of pure Cu (cathode) become
thick. The reactions in the cell are:
At cathode (oxidation):
Cu Cu2+
+ 2e-
At anode (reduction):
Cu2+
+ 2e-
Cu
Thus, there is no net reaction in the cell. However, the net result is the purification of Cu.
vi. Describe galvanic cell.
Galvanic cell:The cell in which a spontaneous redox reaction is used to produce electric current is
called galvanic cell.
Example: Daniel’s cell, Ni-Cd cell, Fuel cell.
vii. Write function of salt bridge?
Functions of salt bridge:
A salt bridge performs following functions:
(a) It connects the solutions of two half - cells and completes the cell circuit.
(b) It prevents transference or diffusion of the solutions from one half cell to the other.
(c) It keeps the solution of two half - cells electrically neutral.
viii. How salt bridge maintains the electrical neutrality?
Two half cells are electrically connected by a salt bridge.
Consider a Zn-Cu cell.
During reaction of this cell, Zn half cell continuously lose their electrons. Thus, in this positive charge
increasing.
Zn Zn2+
+ 2e-
While Cu half cells continuously receive electrons, thus it goes on collecting negative charge.
Cu2+
+ 2e-
Cu

Collection of positive charge in Zn electrode half cell and collection of negative charge in Cu half cell
would stop the reaction.
Salt bridge prevents the net accumulation of charges in either beaker. Thus, from negative Cu half cell.
Negative ions diffuse through the salt bridge into the positive Zn half cell. In this way, salt bridge main-
tains the two solutions, electrically neutral.
ix. Define standard electrode potential. Also differentiate between standard oxidation potential and
standard reduction potential?
Standard electrode potential:
The potential set up when an electrode is in contact with one molar solution of its own ion at 298K is
called standard electrode potential. It is denoted by Eo
.
Sr # Standard oxidation potential Standard reduction potential
1. The potential of an electrode at which
oxidation takes place under standard
conditions is called standard oxidation
potential.
The potential of an electrode at which reduction
takes place under standard conditions is called
standard reduction potential.
2. It is represented as Eo
ox
. It is represented as Eo
red
.
3. Example: Zn Zn2+
+ 2e-
Eo
ox
= 0.76 volts
Example: Cu2+
+ 2e-
Cu
Eo
red
= 0.34 volts
x. Write some applications of electrochemical series?
Applications of electrochemical series:
The emf series has many applications.
1. Prediction of the feasibility of a chemical reaction.
2. Calculation of cell voltage (emf).
3. Comparison of relative tendency of metals and non-metals to get oxidized or reduced.
4. Relative chemical reactivity of metals.
5. Reaction of metals with dilute acid.
6. Displacement f one metal by another from its solution.
xi. The standard oxidation potential of Zn is 0.67V and its reduction potential is -0.67V.
According to the law of conservation of energy, energy can neither be created nor destroyed. Therefore,
if standard oxidation potential of Zn is 0.67V, then its potential for reverse process, i.e. standard reduc-
tion potential will also be same but with positive sign. Thus,
Zn Zn2+
+ 2e-
Eo
ox
= + 0.76V
Zn2+
+ 2e-
Zn Eo
red
= - 0.76V
xii. How do you justify that lead accumulator is chargeable battery ?
It is a re-chargeable car battery.A fully charged battery consists of a cathode of lead oxide (PbO2
) and
anode of metallic lead.The electrolyte is 30% H2
SO4
with density 1.25 g/cm3
.
Two electrodes are connected through an external circuit. It produces electrical current by discharging.
During charging (electrode signs as in charging circuit)
(+) electrode: PbSO4(s)
+ 2H2
O(l)
PbO2(s)
+ 4H+
(aq)
+ SO4
2-
(aq)
+ 2e-
(-) electrode: PbSO4(s)
+ 2e-
Pb(s)
+ SO4
2-
(aq)
Discharging (electrode signs as for cell)
(+) electrode: PbO2(s)
+ 4H+
(aq)
+ SO4
2-
(aq)
+ 2e-
PbSO4(s)
+ 2H2
O(l)
(-) electrode: Pb(s)
+ SO4
2-
(aq)
PbSO4(s)
+ 2e-
The overall, reversible cell reaction is therefore:

PbO2(s)
+ 4H+
(aq)
+ 2SO4
2-
(aq)
+ Pb(s)
2PbSO4(s)
+ 2H2
O(l)
3. Attempt only eight questions 8 X 2 = 16
ii. Differentiate between oxidizing agent and reducing agent?
Sr # Oxidizing agents Reducing agents
1. Oxidizing agent is that substance, which
oxidizes other substances and itself
reduces in a chemical reaction.
Reducing agents are those substances which
reduces the other substances and is oxidized itself
in a redox reaction.
2. Non-metals are oxidizing agents Metals are reducing agents
iii. Differentiate between primary and secondary cells?
Sr # Primary cells Secondary cells
1. These cells cannot be re-charged These cells can be re-charged
2. Example: Alakaline bettery Example: Lead accumulator, Nickle Cadmium etc
iv. What is emf and how we calculate the emf of a galvanic cell?
Emf: Emf (electromotive force) measures the force with which electrons move in th external circuit.
Calculation of emf:
While making galvanic cell, the electrode above in emf series will act as anode, while the electrode
below will act as cathode.
At anode oxidation takes place while at cathode reduction takes place.
Hence cell potential or emf of cell can be determined by using the formula.
Eo
cell
= Eo
(ox)
+ Eo
(red)
e.g. for Zn-Cu cell:
Zn Zn2+
+ 2e-
(oxidation half reaction)
Cu2+
+ 2e-
Cu (reduction half reaction)
________________________________
Zn + Cu2+
Zn2+
+ Cu (complete reaction)
Oxidation potential of Zn is +0.76 volts, while reduction potential of Cu2+
is 0.34 volts, thus
Eo
cell
= Eo
(ox)
+ Eo
(red)
= 0.76+0.34 = 1.10 volts.
Since, Eo
cell
is positive, therefore, this reaction is spontaneous.
v. Why alkali metals react vigorously with water while coinage metals do not react?
Alkali metals are highly reactive due to higher reducing agent power in electrical chemical series while
coinage metals are least reactive because they have high positive reduction potential and low reducing
agent power in electrochemical series.
vi. How anodized aluminium is prepared?
Anodized Al is prepared by making it an anode in an electrolytic cell containing sulphuric acid or chromic

acid. a thin layer of oxide is coated overAl. this layer resists corrosion. The freshly anodizedAl is hydrated
and can absorb dyes.
vii. What is the difference between a cell and a battery?
Battery Cell
In a battery, electrical energy is always generated
from chemical energy .
In cell, electrical energy is converted into
chemical energy.
e.g, lead accumulator E.g. Galvanic cell
viii. What is emf of a cell?
Emf: Emf (electromotive force) measures the force with which electrons move in the external circuit.
Eo
cell
= Eo
(ox)
+ Eo
(red)
ix. Give conditions of electric conduction through electrolytes?
Conditions:
For electrical conduction through electrolysis, following conditions are needed.
• Molten or aqueous solution contains ions is required.
• These ions must conduct electricity.
x. Define electrochemistry and describe electrolytic cell?
Electrochemistry:
Electrochemistry is the branch of chemistry which deals with the conversions of electrical energy into
chemical energy in electrolytic cells as well as conversion of chemical energy into electrical energy in
galvanic or voltaic cell.
Electrochemical cell:
An electrolytic cell in which electric current is used to derive a non-spontaneous redox reaction is
called electrolytic cell.
Example: Down’s cell or Nelson cell.
xi. Difference between down's and nelson cell?
Sr # Down’s Cell Nelson Cell
1. Extraction of sodium by the electrolysis
of fused sodium chloride is carried out in
Down’s cell.
Caustic soda is obtained on industrial scale by
the electrolysis of concentrated aqueous solution
of sodium chloride using titanium mercury or
steel cathode. This electrolysis is carried out in
Nelson Cell.
2. Reaction mechanism is occurred here in
Down’s cell.
NaCl(s)
Na+
(l)
+ Cl-
(l)
At cathode
2Na+
(l)
+ 2e-
2Na(s)
At anode
2Cl-
(l)
2Cl (g)
+ 2e-
Cl (g)
+ Cl (g)
Cl2 (g)
overall reaction
2Na+
(l)
+ 2Cl-
(l)
2Na (s)
+Clo
2(g)
Reaction mechanism is occurred here in Nelson
cell
NaCl(s)
Na+
(l)
+ Cl-
(l)
At Anode
2Cl-
(l)
2Cl (g)
+ 2e-
At Cathode
2H2
O(l)
+ 2e-
H2(g)
+ 20H-
(aq)
Overall reaction
Na+
(aq)
+ 2Cl-
(l)
+2H2
O(l)
H2 (g)
+
2NaOH + Cl2

xii. What is electroplating?
Electroplating:
It is process in which one metal deposited at the surface of another metal. Copper, silver, nickel and
chromium plating is done by various types of electrolytic cells.
4. Attempt any 6 questions 6 x 2 = 12
i. How electrode potential is measured?
The potential of a single electrode can be determined by coupling it with a standard electrode of known
potential such as standard hydrogen electrode (SHE) in galvanic cell. The two solutions are separated
by a porous partition or a salt bridge containing conc. solution KCl. Salt bridge provides a highly con-
ducting path between the two electrolytic solutions. The potential difference is measured by a voltme-
ter.
Since standard electrode potential (oxidation and reduction) of SHE are taken as zero.
Therefore, the measured value of cell potential will be the potential of unknown electrode.
In this way, a series of standard reduction potential can be built up for different electrodes.
ii. Define electrochemical series?
An arrangement of electrodes in the order of increasing reduction potentials, on the basis of stan-
dard hydrogen electrode is called electrochemical series.
iii. Na and K can disperse hydrogen from acids but pt, pd, Cu cannot?
Greater the value of standard reduction potential of a metal, lesser is its tendency to lose electrons to
form metal ions and so weaker is its tendency to displace hydrogen. Since metals like Pt, Pd and Cu
have sufficiently high positive value of reduction potential, therefore, they cannot liberate hydrogen
from acids. On the other hand, Na and K are close to top of electrochemical series and have very low
reduction potential can liberate hydrogen.
iv. Lead accumulator, its desirable and undesirable features?
Desirable features: it is commonly used as car battery. It is secondary or storage cell. Passing a direct
current through it must charge it. The charged cell can then produce electric current when required.
The cathode of a fully charged lead accumulator is lead oxide, PbO2 and its anode is metallic lead. The
electrolyte is 30 % sulphuric acid solution. When the two electrodes are connected through an external
circuit, it produces electricity by discharge. A single cell provide around 2 volts. For 12 volts, 6 cells are
connected in series.
v. What is alkaline battery? Write reactions .
It is a dry alkaline cell. It is non-rechargeable battery. It uses Zn and MnO2
as a reactants
Its reactions are:
Zn(s)
+ 2OH-
(aq)
Zn(OH)2(s)
+ 2e-
2MnO2(aq)
+ H2
O(I)
+ 2e-
Mn2
O3(s)
+ 2OH-
(aq)
vi. Define nickel cadmium cell?
It is a strong cell largely used in NICAD or Ni-Cd battery. It is rechargeable bettery.it is used in battery
operated tools and portable computers. It is also used in cordless razors, photoflash units. Following
reactions takes place in it.

Cd(s)
+ 2OH-
(aq)
Cd(OH2(s)
+ 2e-
NiO2(s)
+ 2H2
O(l)
+ 2e-
Ni(OH)2(s)
+ 2OH-
(aq)
vii. Draw a diagram of hydrogen –oxygen fuel cell?
See diagram from text book.
viii. What are uses of fuel cell?
Uses of fuel cells:
1. Fuel cells are used in space vehicles. Many fuel cells do not produce pollution. Therefore these are used.
2. Fuel cells are very efficient. These cells are the source of electricity therefore, these are used for lights.
3. To get several kilowatts of power, many fuel cells are connected.
Section-Ill: Long Questions.
Attempt any THREE questions. 8 x 3 = 24
5) a) Write note on application of electrochemical series?
b) Write a detailed note on fuel cell?
6) a) Describe the construction and working of standard hydrogen potential?
b) Describe general rules for balancing a redox equation by ion-electron method also balance the follow-
ing equation
MnO4
- +C2
O4
-2
Mn+2
+CO2
7) a) Describe the general rules for balancing a redox equation by oxidation number method. Balance
following equation
FeSO4
+K2
Cr2
O7
+ H2
SO4
K2
SO4
+H2
O +Cr2
(SO4
)3
+Fe2
(SO4
)3
b) Write a note on voltaic or galvanic cell.
8) a) Explain lead accumulator battery with the help of discharging and recharging.
b) Write note on Nickel Cadmium battery and Alkaline battery?
9) a) write working, construction and diagram of electrolytic cell
b) Describe electrolysis process of industrial importance.

F.Sc. Part 1 Chemistry.Ch.10.Test (Malik Xufyan)

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