CBSE Chemistry Past year paper (Solutions) - 2017, Class 12 Class 12 Notes | EduRev

Chemistry Class 12

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Class 12 : CBSE Chemistry Past year paper (Solutions) - 2017, Class 12 Class 12 Notes | EduRev

 Page 1


  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
CBSE 
Class XII Chemistry 
Board Paper 2017 (Solution) 
 
 
1. The formula of an oxo-anion of manganese (Mn) in which it shows the 
oxidation state equal to its group number is 
2
4
MnO
?
.  
In
2
4
MnO
?
, the oxidation state of Mn is 
Mn + (-2 × 4) = -1 
Mn – 8 = -1   
Mn = +7 
The group number of manganese is 7. 
 
2. The IUPAC name of the given compound is N-ethyl-N-methylethanamine. 
   
3. The order of the given reaction is first order. The rate of reaction for the first 
order reaction is independent of the initial concentration of the reaction. 
 
4. Structure of 1-bromo-4-chlorobut-2-ene: 
 
 
 
5. One similarity between physisorption and chemisorption is that the rate of 
adsorption increases with an increase in the surface area of the adsorbent. 
 
6. Completed reactions are   
(i) 
3 2 3
NH 3Cl (excess) NCl 3HCl ? ? ?? ? ? 
(ii) 
6 2 2 2
XeF 2H O XeO F 4HF ? ? ?? ? ? 
 
OR 
(i) When (NH4)2Cr2O7 is heated, it decomposes to produce Cr2O3, H2O and 
N2. 
4 2 2 7 2 3 2 2
(NH ) Cr O Cr O 4H O N
?
? ? ? ? ? ? 
(ii) H2PO3 or orthophosphorous acid (or phosphorous acid) on heating 
dissociates to give orthophosphoric acid or phosphoric acid and 
phosphine. 
3 3 3 4 3
4H PO 3H PO PH
?
? ? ? ? ? 
  
Page 2


  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
CBSE 
Class XII Chemistry 
Board Paper 2017 (Solution) 
 
 
1. The formula of an oxo-anion of manganese (Mn) in which it shows the 
oxidation state equal to its group number is 
2
4
MnO
?
.  
In
2
4
MnO
?
, the oxidation state of Mn is 
Mn + (-2 × 4) = -1 
Mn – 8 = -1   
Mn = +7 
The group number of manganese is 7. 
 
2. The IUPAC name of the given compound is N-ethyl-N-methylethanamine. 
   
3. The order of the given reaction is first order. The rate of reaction for the first 
order reaction is independent of the initial concentration of the reaction. 
 
4. Structure of 1-bromo-4-chlorobut-2-ene: 
 
 
 
5. One similarity between physisorption and chemisorption is that the rate of 
adsorption increases with an increase in the surface area of the adsorbent. 
 
6. Completed reactions are   
(i) 
3 2 3
NH 3Cl (excess) NCl 3HCl ? ? ?? ? ? 
(ii) 
6 2 2 2
XeF 2H O XeO F 4HF ? ? ?? ? ? 
 
OR 
(i) When (NH4)2Cr2O7 is heated, it decomposes to produce Cr2O3, H2O and 
N2. 
4 2 2 7 2 3 2 2
(NH ) Cr O Cr O 4H O N
?
? ? ? ? ? ? 
(ii) H2PO3 or orthophosphorous acid (or phosphorous acid) on heating 
dissociates to give orthophosphoric acid or phosphoric acid and 
phosphine. 
3 3 3 4 3
4H PO 3H PO PH
?
? ? ? ? ? 
  
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
7.   
(i) Colligative properties: Properties of solutions which depend on the 
number of solute particles and are independent of their chemical identity 
or their nature relative to the total number of particles present in the 
solution are called colligative properties.  
Examples: Lowering of vapour pressure, elevation of boiling point, 
depression of freezing point, osmotic pressure 
 
(ii) Molality: Molality (m) is the number of moles of the solute per kilogram 
(kg) of the solvent. It is expressed as  
 
   
Molesof soluteinkg
Molality(m)
Molesof solventinkg
?
 
 
  Example: 1.00 mol kg
-1
 (or 1.00 m) solution of KCl means that 1 mol 
(74.5 g) of KCl is dissolved in 1 kg of water. 
 
8.    
(i) Structure of H2S2O7: 
 
 
(ii) Structure of XeF6: 
 
 
 
9. Degree of dissociation of a weak electrolyte is given by the relation: 
m m
m
m
Where,
degreeof dissociationof theelectrolyte
molar conducivity
molar conductivity atinf inf initedilution
? ? ? ??
??
??
? ? ?
 
 
 
Page 3


  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
CBSE 
Class XII Chemistry 
Board Paper 2017 (Solution) 
 
 
1. The formula of an oxo-anion of manganese (Mn) in which it shows the 
oxidation state equal to its group number is 
2
4
MnO
?
.  
In
2
4
MnO
?
, the oxidation state of Mn is 
Mn + (-2 × 4) = -1 
Mn – 8 = -1   
Mn = +7 
The group number of manganese is 7. 
 
2. The IUPAC name of the given compound is N-ethyl-N-methylethanamine. 
   
3. The order of the given reaction is first order. The rate of reaction for the first 
order reaction is independent of the initial concentration of the reaction. 
 
4. Structure of 1-bromo-4-chlorobut-2-ene: 
 
 
 
5. One similarity between physisorption and chemisorption is that the rate of 
adsorption increases with an increase in the surface area of the adsorbent. 
 
6. Completed reactions are   
(i) 
3 2 3
NH 3Cl (excess) NCl 3HCl ? ? ?? ? ? 
(ii) 
6 2 2 2
XeF 2H O XeO F 4HF ? ? ?? ? ? 
 
OR 
(i) When (NH4)2Cr2O7 is heated, it decomposes to produce Cr2O3, H2O and 
N2. 
4 2 2 7 2 3 2 2
(NH ) Cr O Cr O 4H O N
?
? ? ? ? ? ? 
(ii) H2PO3 or orthophosphorous acid (or phosphorous acid) on heating 
dissociates to give orthophosphoric acid or phosphoric acid and 
phosphine. 
3 3 3 4 3
4H PO 3H PO PH
?
? ? ? ? ? 
  
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
7.   
(i) Colligative properties: Properties of solutions which depend on the 
number of solute particles and are independent of their chemical identity 
or their nature relative to the total number of particles present in the 
solution are called colligative properties.  
Examples: Lowering of vapour pressure, elevation of boiling point, 
depression of freezing point, osmotic pressure 
 
(ii) Molality: Molality (m) is the number of moles of the solute per kilogram 
(kg) of the solvent. It is expressed as  
 
   
Molesof soluteinkg
Molality(m)
Molesof solventinkg
?
 
 
  Example: 1.00 mol kg
-1
 (or 1.00 m) solution of KCl means that 1 mol 
(74.5 g) of KCl is dissolved in 1 kg of water. 
 
8.    
(i) Structure of H2S2O7: 
 
 
(ii) Structure of XeF6: 
 
 
 
9. Degree of dissociation of a weak electrolyte is given by the relation: 
m m
m
m
Where,
degreeof dissociationof theelectrolyte
molar conducivity
molar conductivity atinf inf initedilution
? ? ? ??
??
??
? ? ?
 
 
 
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
 
Given  
21
21
3
21
m
(H ) 349.6Scm mol
(CH COO ) 40.9Scm mol
Molar conducvtivity( ) 39.05Scm mol
??
??
?
? ? ?
? ? ?
??
 
 
Hence, limiting molar conductivity of acetic acid is 
 
m3
21
acetic acid (H ) (CH COO )
40.9 349.8
390.7cm mol
??
?
? ? ? ? ? ? ? ?
??
?
 
Degree of dissociation of acetic acid, 
   
m m
39.05
390.7
0.0999
0.1
? ? ? ??
?
?
?
 
Degree of dissociation of acetic acid is 0.1. 
 
10.  
(i) Wolff–Kishner reduction 
 
 
 
(ii) Etard reaction 
 
 
  
Page 4


  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
CBSE 
Class XII Chemistry 
Board Paper 2017 (Solution) 
 
 
1. The formula of an oxo-anion of manganese (Mn) in which it shows the 
oxidation state equal to its group number is 
2
4
MnO
?
.  
In
2
4
MnO
?
, the oxidation state of Mn is 
Mn + (-2 × 4) = -1 
Mn – 8 = -1   
Mn = +7 
The group number of manganese is 7. 
 
2. The IUPAC name of the given compound is N-ethyl-N-methylethanamine. 
   
3. The order of the given reaction is first order. The rate of reaction for the first 
order reaction is independent of the initial concentration of the reaction. 
 
4. Structure of 1-bromo-4-chlorobut-2-ene: 
 
 
 
5. One similarity between physisorption and chemisorption is that the rate of 
adsorption increases with an increase in the surface area of the adsorbent. 
 
6. Completed reactions are   
(i) 
3 2 3
NH 3Cl (excess) NCl 3HCl ? ? ?? ? ? 
(ii) 
6 2 2 2
XeF 2H O XeO F 4HF ? ? ?? ? ? 
 
OR 
(i) When (NH4)2Cr2O7 is heated, it decomposes to produce Cr2O3, H2O and 
N2. 
4 2 2 7 2 3 2 2
(NH ) Cr O Cr O 4H O N
?
? ? ? ? ? ? 
(ii) H2PO3 or orthophosphorous acid (or phosphorous acid) on heating 
dissociates to give orthophosphoric acid or phosphoric acid and 
phosphine. 
3 3 3 4 3
4H PO 3H PO PH
?
? ? ? ? ? 
  
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
7.   
(i) Colligative properties: Properties of solutions which depend on the 
number of solute particles and are independent of their chemical identity 
or their nature relative to the total number of particles present in the 
solution are called colligative properties.  
Examples: Lowering of vapour pressure, elevation of boiling point, 
depression of freezing point, osmotic pressure 
 
(ii) Molality: Molality (m) is the number of moles of the solute per kilogram 
(kg) of the solvent. It is expressed as  
 
   
Molesof soluteinkg
Molality(m)
Molesof solventinkg
?
 
 
  Example: 1.00 mol kg
-1
 (or 1.00 m) solution of KCl means that 1 mol 
(74.5 g) of KCl is dissolved in 1 kg of water. 
 
8.    
(i) Structure of H2S2O7: 
 
 
(ii) Structure of XeF6: 
 
 
 
9. Degree of dissociation of a weak electrolyte is given by the relation: 
m m
m
m
Where,
degreeof dissociationof theelectrolyte
molar conducivity
molar conductivity atinf inf initedilution
? ? ? ??
??
??
? ? ?
 
 
 
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
 
Given  
21
21
3
21
m
(H ) 349.6Scm mol
(CH COO ) 40.9Scm mol
Molar conducvtivity( ) 39.05Scm mol
??
??
?
? ? ?
? ? ?
??
 
 
Hence, limiting molar conductivity of acetic acid is 
 
m3
21
acetic acid (H ) (CH COO )
40.9 349.8
390.7cm mol
??
?
? ? ? ? ? ? ? ?
??
?
 
Degree of dissociation of acetic acid, 
   
m m
39.05
390.7
0.0999
0.1
? ? ? ??
?
?
?
 
Degree of dissociation of acetic acid is 0.1. 
 
10.  
(i) Wolff–Kishner reduction 
 
 
 
(ii) Etard reaction 
 
 
  
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
11.    
12 22 11
-1
f
Solution:
Molarmassof sugar(C H O )=12x12+22x1+11x16
=342gmol
?T = 2 7 3 . 1 5 -2 6 9 . 1 5
=4K
10% solutionof sucrosemeans10gof canesugar ispresent
=100-10=90gof water
10
No.of molesof cane sugar=
342
=029mol
molalityof the solu
-1
ff
f
-1
6 12 6
-1
0.029x1000
tion=
90
=0.324molkg
Weknow,
?T = K x m
4
K=
0.324
=12.334Kkgmol
Molarmassof glucose(C H O )=6x12+12x1+6x16
=180gmol
10% solutionof glucose means10gof canesugar ispresent
=100-10
=90gof water
Number of moles
-1
ff
10
of glucose= mol=0.055mol
180
0.055x1000
Molalityof the solution= =0.616molkg
90
Usingthe relation,
?T = K x m
=12.33x0.616
=7.6
Therefore,the freezing pointof10%glucose solution=273.15-7.6
=265.5K
 
  
Page 5


  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
CBSE 
Class XII Chemistry 
Board Paper 2017 (Solution) 
 
 
1. The formula of an oxo-anion of manganese (Mn) in which it shows the 
oxidation state equal to its group number is 
2
4
MnO
?
.  
In
2
4
MnO
?
, the oxidation state of Mn is 
Mn + (-2 × 4) = -1 
Mn – 8 = -1   
Mn = +7 
The group number of manganese is 7. 
 
2. The IUPAC name of the given compound is N-ethyl-N-methylethanamine. 
   
3. The order of the given reaction is first order. The rate of reaction for the first 
order reaction is independent of the initial concentration of the reaction. 
 
4. Structure of 1-bromo-4-chlorobut-2-ene: 
 
 
 
5. One similarity between physisorption and chemisorption is that the rate of 
adsorption increases with an increase in the surface area of the adsorbent. 
 
6. Completed reactions are   
(i) 
3 2 3
NH 3Cl (excess) NCl 3HCl ? ? ?? ? ? 
(ii) 
6 2 2 2
XeF 2H O XeO F 4HF ? ? ?? ? ? 
 
OR 
(i) When (NH4)2Cr2O7 is heated, it decomposes to produce Cr2O3, H2O and 
N2. 
4 2 2 7 2 3 2 2
(NH ) Cr O Cr O 4H O N
?
? ? ? ? ? ? 
(ii) H2PO3 or orthophosphorous acid (or phosphorous acid) on heating 
dissociates to give orthophosphoric acid or phosphoric acid and 
phosphine. 
3 3 3 4 3
4H PO 3H PO PH
?
? ? ? ? ? 
  
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
7.   
(i) Colligative properties: Properties of solutions which depend on the 
number of solute particles and are independent of their chemical identity 
or their nature relative to the total number of particles present in the 
solution are called colligative properties.  
Examples: Lowering of vapour pressure, elevation of boiling point, 
depression of freezing point, osmotic pressure 
 
(ii) Molality: Molality (m) is the number of moles of the solute per kilogram 
(kg) of the solvent. It is expressed as  
 
   
Molesof soluteinkg
Molality(m)
Molesof solventinkg
?
 
 
  Example: 1.00 mol kg
-1
 (or 1.00 m) solution of KCl means that 1 mol 
(74.5 g) of KCl is dissolved in 1 kg of water. 
 
8.    
(i) Structure of H2S2O7: 
 
 
(ii) Structure of XeF6: 
 
 
 
9. Degree of dissociation of a weak electrolyte is given by the relation: 
m m
m
m
Where,
degreeof dissociationof theelectrolyte
molar conducivity
molar conductivity atinf inf initedilution
? ? ? ??
??
??
? ? ?
 
 
 
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
 
Given  
21
21
3
21
m
(H ) 349.6Scm mol
(CH COO ) 40.9Scm mol
Molar conducvtivity( ) 39.05Scm mol
??
??
?
? ? ?
? ? ?
??
 
 
Hence, limiting molar conductivity of acetic acid is 
 
m3
21
acetic acid (H ) (CH COO )
40.9 349.8
390.7cm mol
??
?
? ? ? ? ? ? ? ?
??
?
 
Degree of dissociation of acetic acid, 
   
m m
39.05
390.7
0.0999
0.1
? ? ? ??
?
?
?
 
Degree of dissociation of acetic acid is 0.1. 
 
10.  
(i) Wolff–Kishner reduction 
 
 
 
(ii) Etard reaction 
 
 
  
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
11.    
12 22 11
-1
f
Solution:
Molarmassof sugar(C H O )=12x12+22x1+11x16
=342gmol
?T = 2 7 3 . 1 5 -2 6 9 . 1 5
=4K
10% solutionof sucrosemeans10gof canesugar ispresent
=100-10=90gof water
10
No.of molesof cane sugar=
342
=029mol
molalityof the solu
-1
ff
f
-1
6 12 6
-1
0.029x1000
tion=
90
=0.324molkg
Weknow,
?T = K x m
4
K=
0.324
=12.334Kkgmol
Molarmassof glucose(C H O )=6x12+12x1+6x16
=180gmol
10% solutionof glucose means10gof canesugar ispresent
=100-10
=90gof water
Number of moles
-1
ff
10
of glucose= mol=0.055mol
180
0.055x1000
Molalityof the solution= =0.616molkg
90
Usingthe relation,
?T = K x m
=12.33x0.616
=7.6
Therefore,the freezing pointof10%glucose solution=273.15-7.6
=265.5K
 
  
  
 
CBSE  XII  CHEMISTRY 
Board Paper – 2017 Solution 
 
     
12.   
(i) Solution: 
t = 15 min  
  = 900 s 
 I= 2A 
Molar mass of Ag = 108 gmol
-1
 
1 F = 96500 C mol
-1 
Q=It
Q=2 900
Q=1800 C
? 
From the reaction, 
Ag
+
 + e
-
 ? Ag 
 
Mass of Ag deposited 
QM
 
nF
108  1800
1  96500
 2.01 g
?
?
?
?
?
 
Mass of Ag deposited is 2.01 g. 
 
(ii) A fuel cell is an electrochemical cell which converts chemical energy of a 
spontaneous redox reaction to electrical energy. 
 
13.  
(i) Coordination isomerism 
(ii) In [Ni(H2O)6]
2+
, Ni
2+
 ion has two unpaired electrons, and hence, it is 
coloured. 
In [Ni(CN)4]
2-
, there is no unpaired electron, and hence, it is colourless. 
(iii) Pentaamminecarbonatocobalt(III) chloride 
 
14.    
(i)    
Lyophilic sol Lyophobic sol 
Relatively stable as strong forces 
of interaction exist between 
colloidal particles and liquid. 
Less stable as weak forces of 
interaction exist between colloidal 
particles and liquid. 
 
    
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