F.Sc.2.Chemistry.Ch.2.Test Solved-Malik Xufyan Cell # 03137355727

1. F.Sc.2.Chemistry.Ch.2.Test Solved Malik Xufyan
Cell # 0313-7355727
Name: Class: 12 Portion Inorganic
Paper: Chemistry Subjective Part Marks: 68
Time: 2:40 Test: 12 Chapter no: 2
SECTON –I
Q 2. Give the short answers of the following EIGHT questions.
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i. Give the occurrence of alkali metals.
Alkali metals are highly reactive. Therefore, they do not occur free in nature. They are found
in combined state. Most of earth crust is made up of insoluble alumino silicates of alkali
metals.
 Na and K are more abundant and constitute to about 2.4% of earth crust.
 Li is found as complex mineral which are widely distributed. An important
commercial source of Li is the mineral spodumene i.e. Li Al (SiO3)2.
 Small amounts of Rb and Cs are found in K salts deposits.
 Fr is not occurring in nature. It is radioactive element. It is produced in laboratory by
nuclear reaction. It is very unstable, therefore, its chemistry is not well known.
ii. Define alkaline earth metals.
Elements of group IIA elements are called alkaline earth metals. They form ionic compounds.
They show +2 oxidation states. They have two electrons in ‘s’ orbital of their valance shell.
iii. What is meant by the peculiar behavior of lithium?
First member of each main group of periodic table does not follow the regular trends of the
group. Similarly Li shows difference from its family members. This behavior is due to the
following reasons.
 Both Li and Li+
ions have very small size.
 Li+
has high charge density.
 Li has less electropositivity than sodium.
iv. What is meant by solubilities and lattice energies of alkali metals?
Cations of alkali metals have low charge and large radii than the radius of any cations from
the same period. Thus lattice energies of their salts are low. Hence, most of the simple salts
of alkali metals are water-soluble. Most of the salts are ionized completely in aqueous
solution.
v. Give some reaction of oxygen with alkali metals.
Some reactions of oxygen with alkali metals are:
4Li + O2 2Li2O
Li2O + CO2 Li2CO3
4Na + O2 2Na2O
Rb + O2 RbO2
vi. How alkali metals react with water? Give some reactions.

2. F.Sc.2.Chemistry.Ch.2.Test Solved Malik Xufyan
Cell # 0313-7355727
Alkali metals react with water rapidly. A small piece of sodium or potassium or lithium floats
on water and it reacts vigorously with water to liberate hydrogen and form metal hydroxide.
The reaction is highly exothermic. The heat is released may ignite the hydrogen.
2Na + 2H2O 2NaOH + H2
vii. How hydrogen and sulpher react with alkaline earth metals?
Reaction with Hydrogen:
Mg + H2
Pressure
MgI
Mg H2
Ca + H2 CaH2
Reaction with sulpher:
Mg + S MgS
viii. Why the aqueous solution of Na2 CO3 is alkaline in nature?
Na2CO3 is hydrolyzed by water to give alkaline solution. In water, Na2CO3 ionized to give
carbonate anions. Na2CO3 2Na⁺ + CO3
2ˉ
Hydrolysis of carbonate anion gives strong alkaline NaOH, which is greatly ionized. While
carbonic acid produced, is a weak acid and is not greatly ionized. Thus, solution of Na2CO3
shows alkaline nature.
CO3
2ˉ
+ 2H2O H2CO3 + 2OHˉ
Overall reaction is
Na2CO3 +2H2O 2NaOH + H2CO3
Strong alkali weaker acid
ix. Give some differences of alkali metals with alkaline earth metals.
Sr # Alkali metals Alkaline earth metals
1. They have one electron in their outermost
s-orbital.
They have two electrons in their
outermost s-orbital.
2. They are lighter than water. They are heavier than water.
3. They have relatively low values of heat of
hydration and ionization energies.
They have relatively high values of
hydration and ionization energies.
4. They have low melting and boiling points
than alkaline earth metals.
They have high melting and boiling
points than alkali metals.
5. They decompose water vigorously at room
temperature.
2Na + 2H2O 2NaOH + H2
They decompose water less vigorously.
Mg + H2O MgO + H2
6. They are highly electropositive. They are less electropositive.
x. Compare some physical and chemical properties of alkali metals with those of
alkaline earth metals.
i) Elements of both groups react with water to give hydroxides and hydrogen.

3. F.Sc.2.Chemistry.Ch.2.Test Solved Malik Xufyan
Cell # 0313-7355727
ii) Elements of both groups do not occur free in nature.
iii) All the elements of both groups can conduct heat and electricity.
iv) All the elements of both groups are soft and silvery white metal.
v) Elements of both groups are electropositive.
vi) Melting points, boiling points, hardness, ionization energy decreases down the group.
vii)Atomic volume, electropositivity and atomic radii increase down the group.
xi. How diaphragm cell worked? Explain.
Working of diaphragm cell is following;
 Brine is introduced into the cell and its constant level is maintained during the
process.
 When electricity is passed Cl2 rises into the dome at the top of the anode while H2 .s
liberated at cathode and escapes through a pipe, where they are collected.
 NaOH solution slowly moves downward through the diaphragm and is collected in a
catch basin below diaphragm.
xii. What is meant by hard finish Plasters?
Hard finish plasters are produced by calcinations of anhydrous sulphate with alum or borax.
These plasters set very slowly but give hard finish.
When plaster of paris is mixed with wood pulp and allowed to set in the form of boards, then
a material is obtained which is used in the construction of buildings as wall boards and
partitions.
Q 2. Give the short answers of the following EIGHT questions.
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i. What happened when lithium hydroxide is treated with water?
Lithium hydroxide produced hydrogen when it is treated with water.
LiH + H2O LiOH + H2
ii. Why lime water turns milky with CO2 but become clear with excess CO2?
Lime water is solution of lime CaO in water. When CaO is dissolved in water, it reacts with
water to produced Ca (OH)2. When CO2 is passed through lime water it reacts with Ca (OH)2
and produced CaCO3.
Ca(OH)2 + CO2 CaCO3 + H2O
The milkyness disappears when excess CO2 is passed through it due to the formation of
Ca(HCO3)2, which is soluble in water.
Ca(OH)2 + CO2 CaCO3 + H2O
CaCO3 + CO2 + H2O Ca(HCO3)2
iii. How gypsum is converted into plaster of Paris?
When gypsum is heated at 100˚C it loses 3/4th
of its water and changes to plaster of Paris.
2CaSO4.2H2O CaSO4)2.H2O + 3H2O
Or
CaSO4 .H2O CaSO4.⅟2H2O + H2O
iv. How lime mortar is prepared?

4. F.Sc.2.Chemistry.Ch.2.Test Solved Malik Xufyan
Cell # 0313-7355727
Ordinary mortar is also called lime mortar, is prepared by mixing freshly slaked lime with
sand and water to form a thick paste. Mortar is made by mixing freshly slaked lime (one
volume), sand (three or four volumes) and water to make thick paste. This material is
hardened or sets when placed b/w stones and bricks. Thus, it binds the blocks firmly together.
The reactions for this process are
CaO + H2O Ca(OH)2
Ca(OH)2 + CO2 CaCO3 + H2O
Ca(OH)2 + SiO2 CaSiO3 + H2O
v. How lime and sand are used to make glass?
Lime and sand react at high temperature to form calcium silicate (CaSiO3). Calcium silicate
is further used in the formation of glass.
vi. Give formulas of following ores:
i) Dolomite ii) Asbestos iii) sylvite iv) Natron
The formula of dolomite is MgCO3.CaCO3.
The formula of asbestos is CaMg3(SiO3)4.
The formula of sylvite is KCl.
The formula of natron is Na2CO3.H2O.
vii. Describe the role of lime in agriculture.
The roles of lime in agriculture are:
i) CaO is used for neutralizing acidic soils.
ii) Application of lime to acidic soil increases the amount of readily soluble
phosphorous.
iii) CaO is used for making lime sulpher sprays which have a strong fungicidal action.
viii. What is meant by slacked lime?
When lime is mixed with water it form calcium hydroxide called slaked lime. This process is
called slaking of lime. It is an exothermic process.
CaO + H2O Ca(OH)2
ix. What type of problems we face during the commercial preparation of NaOH
through diaphragm cell?
Two problems we face. These are;
i) Cl-
produced can react with OH-
ions to give OCl-
ion.
Cl2(g) + 2OH-
(aq) OCl-
(aq) + Cl-
(aq) + H2O
This problem can be removed by using asbestos diaphragm which keeps the two solutions
separate and allow sodium ions to move to cathode. The movement of ions keeps the current
flowing through the external circuit.
ii) OH-
may be attracted to anode where it can discharge to give O2 gas which makes the
liberated Cl2 impure.
It is removed by keeping the level of brine in anode compartment slightly higher. This keeps
the direction of flow of liquid toward the cathode. Thus it prevents the movement of OH-
towards anode.

5. F.Sc.2.Chemistry.Ch.2.Test Solved Malik Xufyan
Cell # 0313-7355727
x. Give the advantages of Down’s cell at 600o
C.
Following advantages are formed;
 The metallic fog is not produced.
 Liquid sodium can be easily collected at 600o
C.
 Product form does not react with material of the cell.
xi. Explain the role of lime in industries.
 Lime is used in paper industry.
 Lime is used in ceramic industry for producing different types of sanitary materials.
 Lime is used in the manufacturing of bleaching powder which is used for bleaching of
the fabric and paper pulp.
 Lime is also used in leather industry.
 A suspension of the calcium hydroxide is called milk of lime and is used as a white-
wash.
 It is used in glass making. Lime reacts with sand at high temperature forming calcium
silicate CaSiO3 which is the basis for glass manufacture.
xii. How gypsum is used in cement industry?
Gypsum is also used in cement industry.
Portland cement is obtained by heating mixture of clay and lime stone. The resulting mass
called clinkers. Then clinkers allow to stand and cooled and crushed into fine powder.
During crushing about 2% gypsum is also added. It prevents the cement from hardening
quickly and increases the setting time of cement so that it can be used easily.
Q 4. Give the short answers of the following SIX questions.
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i. What is the function of Ca in plant growth?
The functions of Ca in plant growth are:
i) Ca is essential for the normal growth of plant. Different plants required different
amount of Ca.
ii) Soils containing Ca are alkaline in nature.
iii) Presence of Ca in soil controls the availability of phosphorous in soil.
iv) Ca is also necessary for normal development of leaves. Sufficient Ca accumulates in
leaves and barks.
ii. What is meant by the setting of plaster of Paris?
When plaster of Paris is mixed with half of its weight of water, it forms a plastic type of
viscous mass which then sets to a hard porous mass. This process completes in 10 to 15 mins.
During this process, solid mass expand 1% by volume and fills the mould completely. Thus,
it gives a sharp impression. This is called setting of plaster of Paris.
iii. Give some uses of plaster of Paris.
It is used
 For making plaster walls.
 For casts of statuary, coins etc.

6. F.Sc.2.Chemistry.Ch.2.Test Solved Malik Xufyan
Cell # 0313-7355727
 In surgery. Its bandages are used to keep fractured bone in place after setting.
iv. Describe the role of gypsum in agriculture.
The roles of gypsum in agriculture is
 Gypsum is an important source of Ca and S.
 S is also an important element for plant growth.
 S is also an important constituent of protein.
 In fertilizers, gypsum supplied Ca to the soil for crop production. It is particularly
important where soils are subject to extensive leaching.
v. What is meant by the carbonates of alkaline earth metals?
Alkaline earth metal carbonates are the only slightly soluble in water. The solubility
decreases down the group. They decompose on heating.
CaCO3 CaO + CO2
MgCO3 MgO + CO2
BaCO3 BaO + CO2
vi. What do you know about the reactivity of alkaline earth metals?
 Alkaline earth metals are very reactive due to low ionization energies.
 The reactivity increases down the group.
 However, alkaline earth metals are less reactive than alkali metals.
vii. What is brine? Give the construction of diaphragm cell.
A concentrated solution of NaCl is called brine.
Construction of diaphragm cell:
 It is an oblong steel tank.
 There is a U-shaped diaphragm in it which holds the salt solution.
 Graphite anode project into the salt solution.
 A current of steam is passed through the cell to keep the salt warm and keep
perforation open.
 Cathode is made up of oblong perforated steel internally lined with asbestos
diaphragm.
 There is a special device, which keeps constant level of salt solution in the cell.
viii. Give the working of Down’s cell.
 NaCl is fed into the cell. Some CaCl2 is also added to lower the melting point of NaCl
from 801o
C to 600o
C. The cell is operated at this temperature.
 When electricity is passed, Na rises in a special compartment from where it is
withdraw from time to time.
 Dry Cl2 gas is collected above anode.
 The process is carried out at 600o
C which has following advantages.
 The metallic fog is not produced.
 Liquid sodium can be easily collected at 600o
C.

7. F.Sc.2.Chemistry.Ch.2.Test Solved Malik Xufyan
Cell # 0313-7355727
 Product form does not react with material of the cell.
ix. How sodium carbonate is very important industrial chemical? Explain.
Sodium carbonate is very important industrial due to its different forms.
Below 35.2o
C, Na2CO3 crystallizes out from water as Na2CO3.10H2O which is called
washing soda.
Above this temperature it crystallizes as Na2CO3.H2O.
On standing in air, Na2CO3.10H2O slowly loses water and converted to a white powder
Na2CO3.H2O.
x. What happens when
 Lithium carbonate is heated.
Li2CO3 LiO + CO2
 Lithium hydroxide is heated to red hot.
2LiOH Li2O + H2O
red hot
 Beryllium is treated with NaOH.
Be + 2NaOH Na2BeO2 + H2
SECTION-ll
Give the answers of the following three questions. Each question is of FOUR marks.
24
Q 5. Explain in detail about the peculiar behavior of following:
A) Lithium B) Beryllium
See the topics of peculiar behavior of lithium of beryllium.
Q 6. A) Give the commercial preparation of sodium by Down’s cell in detail.
See the topic of commercial preparation of sodium by Down’s cell.
B) Give commercial preparation of NaOH by the diaphragm cell in detail.
See the topic of commercial preparation of NaOH by the diaphragm cell.
Q 7. A) Describe the role of gypsum in industry.
See the topic of role of gypsum in industry.
B) Describe the role of lime in industry.
See the topic of role of lime in industry.