Solved Example: s-Block Element | Chemistry for JEE Main & Advanced PDF Download

 Page 1


JEE Solved Example on S Block Element 
JEE Mains 
Q1:  Calgon (a water softener) is: 
(A) ????
?? [????
?? (????
?? )
?? ] 
(B) ????
?? [???? (????
?? )]
?? 
(C) ????
?? [????
?? (????
?? )]
?? 
(D) ????
?? [????
?? (????
?? )
?? ] 
Ans: (A) Calgon: Na
2
[Na
4
(PO
3
)
6
] 
It is a water softer because it removes Ca and Mg ions from hard water by forming a soluble 
complex. 
2Ca
2+
+ Na
2
[Na
4
(PO
3
)
6
? Na
2
[Ca
2
(PO
3
)
6
] + 2Na 
hard water Calgon Soluble complex 
 
Q2: Which gas in cold, liquid form expands when it is further cooled: 
(A) Liquid ???? 
(B) Liquid ????
?? 
(C) Liquid ?? ?? 
(D) Liquid ?? ?? 
Ans: (C) In liquid H
2
, the intermolecular weak attractive forces are dominate then repulsive forces. 
? Liquid H
2
 expands while cooling. 
 
Q3:  Hydrogen has a tendency to gain one electron in order to acquire helium configuration. It thus 
resembles: 
(A) Alkali metals 
(B) Noble gases 
(C) Halogens 
(D) Alkaline earth metals 
Ans:  (C) Hydrogen electronic configuration is 1?? 1
 
? By gaining 1 electron it can acquire helium 1?? 2
 configuration. Hydrogen has a tendency which 
resembles it to halogen because halogens are also only 1 electron has to stable noble gas 
configuration. 
 
Q4:  When a molten metal hydride is electrolysed? 
(A) ?? +
ions produced move towards the cathode 
(B) ?? -
ions produced move towards the anode 
(C) ?? ?? is liberated at anode 
(D) ?? ?? is liberated at cathode 
Page 2


JEE Solved Example on S Block Element 
JEE Mains 
Q1:  Calgon (a water softener) is: 
(A) ????
?? [????
?? (????
?? )
?? ] 
(B) ????
?? [???? (????
?? )]
?? 
(C) ????
?? [????
?? (????
?? )]
?? 
(D) ????
?? [????
?? (????
?? )
?? ] 
Ans: (A) Calgon: Na
2
[Na
4
(PO
3
)
6
] 
It is a water softer because it removes Ca and Mg ions from hard water by forming a soluble 
complex. 
2Ca
2+
+ Na
2
[Na
4
(PO
3
)
6
? Na
2
[Ca
2
(PO
3
)
6
] + 2Na 
hard water Calgon Soluble complex 
 
Q2: Which gas in cold, liquid form expands when it is further cooled: 
(A) Liquid ???? 
(B) Liquid ????
?? 
(C) Liquid ?? ?? 
(D) Liquid ?? ?? 
Ans: (C) In liquid H
2
, the intermolecular weak attractive forces are dominate then repulsive forces. 
? Liquid H
2
 expands while cooling. 
 
Q3:  Hydrogen has a tendency to gain one electron in order to acquire helium configuration. It thus 
resembles: 
(A) Alkali metals 
(B) Noble gases 
(C) Halogens 
(D) Alkaline earth metals 
Ans:  (C) Hydrogen electronic configuration is 1?? 1
 
? By gaining 1 electron it can acquire helium 1?? 2
 configuration. Hydrogen has a tendency which 
resembles it to halogen because halogens are also only 1 electron has to stable noble gas 
configuration. 
 
Q4:  When a molten metal hydride is electrolysed? 
(A) ?? +
ions produced move towards the cathode 
(B) ?? -
ions produced move towards the anode 
(C) ?? ?? is liberated at anode 
(D) ?? ?? is liberated at cathode 
Ans: (C) H
-
is oxidised at anode to H
2
 
 
Q5:  Which is true statement? 
(A) The layer of ice on the surface of river in the winter acts as a thermal insulator between the 
water below and the air above 
(B) The fish and other marine organism are enabled to survive long periods of freezing water due 
to the fact that ice is lighter than water 
(C) Both is correct 
(D) None is correct 
Ans: (C) Ice is lighter than water because ice has less density than water for this hydrogen bonding is 
responsible. 
 
Q6:  A sample of water contains sodium chloride. It is 
(A) Hard water 
(B) Soft water 
(C) Moderately hard 
(D) None of these 
Ans: (B) NaCl is soluble salt 
? It is soft water 
 
Q7:  The bleaching properties of ?? ?? ?? ?? are due to its 
(A) Reducing properties 
(B) Oxidising properties 
(C) Unstable nature 
(D) Acidic nature 
Ans: (B) H
2
O
2
 show oxidising as well as reducing properties 
? H
2
O
2
 bleaching properties is due to its oxidising nature. 
 
Q8:  When ???? % solution of ?? ?? ????
?? is electrolysed by passing a current of high density at low 
temperature the main products of electrolysis are 
(A) Oxygen and hydrogen 
(B) ?? ?? and peroxy disulphuric acid 
(C) ?? ?? and ????
?? 
(D) ?? ?? and peroxy disulphuric acid 
Ans: (B) 
Page 3


JEE Solved Example on S Block Element 
JEE Mains 
Q1:  Calgon (a water softener) is: 
(A) ????
?? [????
?? (????
?? )
?? ] 
(B) ????
?? [???? (????
?? )]
?? 
(C) ????
?? [????
?? (????
?? )]
?? 
(D) ????
?? [????
?? (????
?? )
?? ] 
Ans: (A) Calgon: Na
2
[Na
4
(PO
3
)
6
] 
It is a water softer because it removes Ca and Mg ions from hard water by forming a soluble 
complex. 
2Ca
2+
+ Na
2
[Na
4
(PO
3
)
6
? Na
2
[Ca
2
(PO
3
)
6
] + 2Na 
hard water Calgon Soluble complex 
 
Q2: Which gas in cold, liquid form expands when it is further cooled: 
(A) Liquid ???? 
(B) Liquid ????
?? 
(C) Liquid ?? ?? 
(D) Liquid ?? ?? 
Ans: (C) In liquid H
2
, the intermolecular weak attractive forces are dominate then repulsive forces. 
? Liquid H
2
 expands while cooling. 
 
Q3:  Hydrogen has a tendency to gain one electron in order to acquire helium configuration. It thus 
resembles: 
(A) Alkali metals 
(B) Noble gases 
(C) Halogens 
(D) Alkaline earth metals 
Ans:  (C) Hydrogen electronic configuration is 1?? 1
 
? By gaining 1 electron it can acquire helium 1?? 2
 configuration. Hydrogen has a tendency which 
resembles it to halogen because halogens are also only 1 electron has to stable noble gas 
configuration. 
 
Q4:  When a molten metal hydride is electrolysed? 
(A) ?? +
ions produced move towards the cathode 
(B) ?? -
ions produced move towards the anode 
(C) ?? ?? is liberated at anode 
(D) ?? ?? is liberated at cathode 
Ans: (C) H
-
is oxidised at anode to H
2
 
 
Q5:  Which is true statement? 
(A) The layer of ice on the surface of river in the winter acts as a thermal insulator between the 
water below and the air above 
(B) The fish and other marine organism are enabled to survive long periods of freezing water due 
to the fact that ice is lighter than water 
(C) Both is correct 
(D) None is correct 
Ans: (C) Ice is lighter than water because ice has less density than water for this hydrogen bonding is 
responsible. 
 
Q6:  A sample of water contains sodium chloride. It is 
(A) Hard water 
(B) Soft water 
(C) Moderately hard 
(D) None of these 
Ans: (B) NaCl is soluble salt 
? It is soft water 
 
Q7:  The bleaching properties of ?? ?? ?? ?? are due to its 
(A) Reducing properties 
(B) Oxidising properties 
(C) Unstable nature 
(D) Acidic nature 
Ans: (B) H
2
O
2
 show oxidising as well as reducing properties 
? H
2
O
2
 bleaching properties is due to its oxidising nature. 
 
Q8:  When ???? % solution of ?? ?? ????
?? is electrolysed by passing a current of high density at low 
temperature the main products of electrolysis are 
(A) Oxygen and hydrogen 
(B) ?? ?? and peroxy disulphuric acid 
(C) ?? ?? and ????
?? 
(D) ?? ?? and peroxy disulphuric acid 
Ans: (B) 
 
Q9:  Hardness producing salt, whose solubility in water decreases with rise of temperature is- 
(A) ???????? ?? 
(B) ???????? ?? 
(C) ???? (?????? ?? )
?? 
(D) ???????? ?? 
Ans: (B) CaSO
4
 is a hardness producing salt and its solubility changes with rise in temperature. Its 
solubility increases till and then decreases when increases temperature beyond that 
 
Q10:  Hydrolysis of one mole of peroxy disulphuric acid produces: 
(A) Two moles of sulphuric acid 
(B) Two moles of peroxymono sulphuric acid 
(C) One mole of sulphuric acid and one mole of peroxy mono sulphuric acid 
(D) One mole of sulphuric acid, one mole of peroxy monosulphuric acid and one mole of hydrogen 
peroxide. 
Ans: (C) 
Page 4


JEE Solved Example on S Block Element 
JEE Mains 
Q1:  Calgon (a water softener) is: 
(A) ????
?? [????
?? (????
?? )
?? ] 
(B) ????
?? [???? (????
?? )]
?? 
(C) ????
?? [????
?? (????
?? )]
?? 
(D) ????
?? [????
?? (????
?? )
?? ] 
Ans: (A) Calgon: Na
2
[Na
4
(PO
3
)
6
] 
It is a water softer because it removes Ca and Mg ions from hard water by forming a soluble 
complex. 
2Ca
2+
+ Na
2
[Na
4
(PO
3
)
6
? Na
2
[Ca
2
(PO
3
)
6
] + 2Na 
hard water Calgon Soluble complex 
 
Q2: Which gas in cold, liquid form expands when it is further cooled: 
(A) Liquid ???? 
(B) Liquid ????
?? 
(C) Liquid ?? ?? 
(D) Liquid ?? ?? 
Ans: (C) In liquid H
2
, the intermolecular weak attractive forces are dominate then repulsive forces. 
? Liquid H
2
 expands while cooling. 
 
Q3:  Hydrogen has a tendency to gain one electron in order to acquire helium configuration. It thus 
resembles: 
(A) Alkali metals 
(B) Noble gases 
(C) Halogens 
(D) Alkaline earth metals 
Ans:  (C) Hydrogen electronic configuration is 1?? 1
 
? By gaining 1 electron it can acquire helium 1?? 2
 configuration. Hydrogen has a tendency which 
resembles it to halogen because halogens are also only 1 electron has to stable noble gas 
configuration. 
 
Q4:  When a molten metal hydride is electrolysed? 
(A) ?? +
ions produced move towards the cathode 
(B) ?? -
ions produced move towards the anode 
(C) ?? ?? is liberated at anode 
(D) ?? ?? is liberated at cathode 
Ans: (C) H
-
is oxidised at anode to H
2
 
 
Q5:  Which is true statement? 
(A) The layer of ice on the surface of river in the winter acts as a thermal insulator between the 
water below and the air above 
(B) The fish and other marine organism are enabled to survive long periods of freezing water due 
to the fact that ice is lighter than water 
(C) Both is correct 
(D) None is correct 
Ans: (C) Ice is lighter than water because ice has less density than water for this hydrogen bonding is 
responsible. 
 
Q6:  A sample of water contains sodium chloride. It is 
(A) Hard water 
(B) Soft water 
(C) Moderately hard 
(D) None of these 
Ans: (B) NaCl is soluble salt 
? It is soft water 
 
Q7:  The bleaching properties of ?? ?? ?? ?? are due to its 
(A) Reducing properties 
(B) Oxidising properties 
(C) Unstable nature 
(D) Acidic nature 
Ans: (B) H
2
O
2
 show oxidising as well as reducing properties 
? H
2
O
2
 bleaching properties is due to its oxidising nature. 
 
Q8:  When ???? % solution of ?? ?? ????
?? is electrolysed by passing a current of high density at low 
temperature the main products of electrolysis are 
(A) Oxygen and hydrogen 
(B) ?? ?? and peroxy disulphuric acid 
(C) ?? ?? and ????
?? 
(D) ?? ?? and peroxy disulphuric acid 
Ans: (B) 
 
Q9:  Hardness producing salt, whose solubility in water decreases with rise of temperature is- 
(A) ???????? ?? 
(B) ???????? ?? 
(C) ???? (?????? ?? )
?? 
(D) ???????? ?? 
Ans: (B) CaSO
4
 is a hardness producing salt and its solubility changes with rise in temperature. Its 
solubility increases till and then decreases when increases temperature beyond that 
 
Q10:  Hydrolysis of one mole of peroxy disulphuric acid produces: 
(A) Two moles of sulphuric acid 
(B) Two moles of peroxymono sulphuric acid 
(C) One mole of sulphuric acid and one mole of peroxy mono sulphuric acid 
(D) One mole of sulphuric acid, one mole of peroxy monosulphuric acid and one mole of hydrogen 
peroxide. 
Ans: (C) 
 
Q11:  Which of the following is not a redox reaction 
 (A) ?????? + ?? ?? ????
?? ?? ?? + con. ?? ?? ????
?? ? ?????? ?? ????
?? + ?? ?? ????
?? +?? ?? ?? 
 (B) ?? ?? ????
?? ?? ?? + ?? ?? ?? ?? + con. ?? ?? ????
?? ? ?? ?? ????
?? + ?????? ?? +?? ?? ?? 
(C) ?? ?? ????
?? ?? ?? + ?? ?? ?? ?? + dil. ?? ?? ????
?? ? ?? ?? ????
?? + ????
?? (????
?? )
?? +?? ?? ?? ?? + ?? ?? ?? 
(D) ?? ?? ????
?? ?? ?? + ???????? ? ?? ?? ?? ?????? ?? + ?? ?? ?? 
Ans: (D) K
2
 
-6
Cr
2
O
7
+ 2KOH ? 2 K
2
 
-6
CrO
4
+ H
2
O 
No change in oxidation state and no loss/gain of electron. 
? Not a redox reaction 
 
 
Q12:  A sample of water containing some dissolved table sugar and common salt is passed through 
organic ion exchange resins. The resulting water will be - 
(A) Tasteless 
(B) Sweet 
(C) Salty 
(D) None of these 
Ans: (B) Water + sugar + salt ?
?
?
 organic resins are generally used to soften the water. 
When water is passed through it since Na
+
, Ca
2+
, Mg
2-
 can be more attracted. So, resins attract 
them more and release H
+
in the water. 
? NaCl can be removed from water and water turns sweet. 
 
 
Page 5


JEE Solved Example on S Block Element 
JEE Mains 
Q1:  Calgon (a water softener) is: 
(A) ????
?? [????
?? (????
?? )
?? ] 
(B) ????
?? [???? (????
?? )]
?? 
(C) ????
?? [????
?? (????
?? )]
?? 
(D) ????
?? [????
?? (????
?? )
?? ] 
Ans: (A) Calgon: Na
2
[Na
4
(PO
3
)
6
] 
It is a water softer because it removes Ca and Mg ions from hard water by forming a soluble 
complex. 
2Ca
2+
+ Na
2
[Na
4
(PO
3
)
6
? Na
2
[Ca
2
(PO
3
)
6
] + 2Na 
hard water Calgon Soluble complex 
 
Q2: Which gas in cold, liquid form expands when it is further cooled: 
(A) Liquid ???? 
(B) Liquid ????
?? 
(C) Liquid ?? ?? 
(D) Liquid ?? ?? 
Ans: (C) In liquid H
2
, the intermolecular weak attractive forces are dominate then repulsive forces. 
? Liquid H
2
 expands while cooling. 
 
Q3:  Hydrogen has a tendency to gain one electron in order to acquire helium configuration. It thus 
resembles: 
(A) Alkali metals 
(B) Noble gases 
(C) Halogens 
(D) Alkaline earth metals 
Ans:  (C) Hydrogen electronic configuration is 1?? 1
 
? By gaining 1 electron it can acquire helium 1?? 2
 configuration. Hydrogen has a tendency which 
resembles it to halogen because halogens are also only 1 electron has to stable noble gas 
configuration. 
 
Q4:  When a molten metal hydride is electrolysed? 
(A) ?? +
ions produced move towards the cathode 
(B) ?? -
ions produced move towards the anode 
(C) ?? ?? is liberated at anode 
(D) ?? ?? is liberated at cathode 
Ans: (C) H
-
is oxidised at anode to H
2
 
 
Q5:  Which is true statement? 
(A) The layer of ice on the surface of river in the winter acts as a thermal insulator between the 
water below and the air above 
(B) The fish and other marine organism are enabled to survive long periods of freezing water due 
to the fact that ice is lighter than water 
(C) Both is correct 
(D) None is correct 
Ans: (C) Ice is lighter than water because ice has less density than water for this hydrogen bonding is 
responsible. 
 
Q6:  A sample of water contains sodium chloride. It is 
(A) Hard water 
(B) Soft water 
(C) Moderately hard 
(D) None of these 
Ans: (B) NaCl is soluble salt 
? It is soft water 
 
Q7:  The bleaching properties of ?? ?? ?? ?? are due to its 
(A) Reducing properties 
(B) Oxidising properties 
(C) Unstable nature 
(D) Acidic nature 
Ans: (B) H
2
O
2
 show oxidising as well as reducing properties 
? H
2
O
2
 bleaching properties is due to its oxidising nature. 
 
Q8:  When ???? % solution of ?? ?? ????
?? is electrolysed by passing a current of high density at low 
temperature the main products of electrolysis are 
(A) Oxygen and hydrogen 
(B) ?? ?? and peroxy disulphuric acid 
(C) ?? ?? and ????
?? 
(D) ?? ?? and peroxy disulphuric acid 
Ans: (B) 
 
Q9:  Hardness producing salt, whose solubility in water decreases with rise of temperature is- 
(A) ???????? ?? 
(B) ???????? ?? 
(C) ???? (?????? ?? )
?? 
(D) ???????? ?? 
Ans: (B) CaSO
4
 is a hardness producing salt and its solubility changes with rise in temperature. Its 
solubility increases till and then decreases when increases temperature beyond that 
 
Q10:  Hydrolysis of one mole of peroxy disulphuric acid produces: 
(A) Two moles of sulphuric acid 
(B) Two moles of peroxymono sulphuric acid 
(C) One mole of sulphuric acid and one mole of peroxy mono sulphuric acid 
(D) One mole of sulphuric acid, one mole of peroxy monosulphuric acid and one mole of hydrogen 
peroxide. 
Ans: (C) 
 
Q11:  Which of the following is not a redox reaction 
 (A) ?????? + ?? ?? ????
?? ?? ?? + con. ?? ?? ????
?? ? ?????? ?? ????
?? + ?? ?? ????
?? +?? ?? ?? 
 (B) ?? ?? ????
?? ?? ?? + ?? ?? ?? ?? + con. ?? ?? ????
?? ? ?? ?? ????
?? + ?????? ?? +?? ?? ?? 
(C) ?? ?? ????
?? ?? ?? + ?? ?? ?? ?? + dil. ?? ?? ????
?? ? ?? ?? ????
?? + ????
?? (????
?? )
?? +?? ?? ?? ?? + ?? ?? ?? 
(D) ?? ?? ????
?? ?? ?? + ???????? ? ?? ?? ?? ?????? ?? + ?? ?? ?? 
Ans: (D) K
2
 
-6
Cr
2
O
7
+ 2KOH ? 2 K
2
 
-6
CrO
4
+ H
2
O 
No change in oxidation state and no loss/gain of electron. 
? Not a redox reaction 
 
 
Q12:  A sample of water containing some dissolved table sugar and common salt is passed through 
organic ion exchange resins. The resulting water will be - 
(A) Tasteless 
(B) Sweet 
(C) Salty 
(D) None of these 
Ans: (B) Water + sugar + salt ?
?
?
 organic resins are generally used to soften the water. 
When water is passed through it since Na
+
, Ca
2+
, Mg
2-
 can be more attracted. So, resins attract 
them more and release H
+
in the water. 
? NaCl can be removed from water and water turns sweet. 
 
 
Q13:  Which of the following reaction does not take place 
(A) ???????? ?? + ???? ? ???????? ?? + ???? 
(B) ???????? ?? + ???? ? ????????
?? + ???? 
(C) ?????? + ?? ?? ?? ? ???????? + ?? ?? 
(D) ????
?? ????
?? + ????
?? ? ????
?? ????
?? + ????
?? 
 
Ans: (D) (A) CuSO
4
+ Zn ? Cu + ZnSO
4
 
This reaction takes place in galvanic cell. 
(B) E
°
 of this reaction is positive 
? Reaction is possible. 
(C) Hydrides react violently with water providing dihydrogen gas. 
(D) Na
2
CO
3
 is better base than Na
2
SO
3
 
? Weak base and acid cannot produce strong base and acid. 
 
 
Q14:  If -?? - ?? bond is weaker than -O-D bond, 
(A) The biological growth of a plant which is fed by ?? ?? ?? is fast 
(B) The biological growth of a plant which is fed by ?? ?? ?? is fast 
(C) The biological growth of a plant which fed both by ?? ?? ?? or ?? ?? ?? are same 
(D) Water does not have any role in plant growth. 
 
Ans: (B) Since bonding vibration of -O - H bond is more than -?? - ?? . Energy required to break the 
bond is less in -O - H than -O - D 
? -O - H bond is weaker than -O - D 
? Biological growth of plant which is fed by H
2
O is fast because it requires less energy to break H
2
O. 
 
Q15:  Water obtained by purification with organic ion Exchange resins is - 
(A) Pure water 
(B) Free from only ????
?? +
, ????
?? +
 ions 
(C) Free from ?????? ?? -
, ????
?? ?? -
 and ????
-
ions only 
(D) None of these 
Ans: (D) Conceptual fact. 
 
Q16: When two ice cubes are pressed over each other, they unite to form one cube. Which of the 
following forces is responsible to hold them together? 
(A) Hydrogen bond formation 
(B) Vander Waals' forces 
(C) Covalent attraction 
(D) Ionic interaction