CBSE Chemistry Past year paper - 2018, Class 12 Class 12 Notes | EduRev

Chemistry Class 12

Class 12 : CBSE Chemistry Past year paper - 2018, Class 12 Class 12 Notes | EduRev

 Page 1


  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
CBSE 
Class XII Chemistry 
Board Paper – 2018 
 
Time: 3 Hours  Total Marks: 70                                                                           
  
General Instructions:    
? Please check this question paper contains 26 questions. 
15 min time has been allotted to read this question paper. 
? The question paper has been distributed at 10.15 am. 
From 10.15 am to 10.30 am, the students will read the question paper only and 
will not write any answer on answer book during this period.                                                                                                                 
 
 
1. Write the coordination number and oxidation state of Platinum in the 
complex [Pt (en)2Cl2]. [1] 
 
2. Analysis shows that FeO has a non-stoichiometric composition with formula 
Fe0-95O. Give reason. [1] 
 
3. Out of chlorobenzene and benzyl chloride, which one gets easily hydrolysed 
by aqueous NaOH and why? [1] 
 
4. Write the IUPAC name of the following: [1] 
3
33
25
          CH
           |
CH  C  CH CH
           |      |
           C H OH
? ? ?  
 
5. CO (g) and H2 (g) react to give different products in the presence of different 
catalysts. Which ability of the catalyst is shown by these reactions? [1] 
 
6. Among the hydrides of Group-15 elements, which have the [2] 
(a) Lowest boiling point? 
(b) Maximum basic character? 
(c) Highest bond angle? 
(d) Maximum reducing character? 
 
7. Calculate the freezing point of a solution containing 60 g of glucose (Molar 
mass = 180g mol
-1
) in 250 g of water. (Kf of water = 1.86 K kg mol
-1
) [2] 
 
 
 
Page 2


  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
CBSE 
Class XII Chemistry 
Board Paper – 2018 
 
Time: 3 Hours  Total Marks: 70                                                                           
  
General Instructions:    
? Please check this question paper contains 26 questions. 
15 min time has been allotted to read this question paper. 
? The question paper has been distributed at 10.15 am. 
From 10.15 am to 10.30 am, the students will read the question paper only and 
will not write any answer on answer book during this period.                                                                                                                 
 
 
1. Write the coordination number and oxidation state of Platinum in the 
complex [Pt (en)2Cl2]. [1] 
 
2. Analysis shows that FeO has a non-stoichiometric composition with formula 
Fe0-95O. Give reason. [1] 
 
3. Out of chlorobenzene and benzyl chloride, which one gets easily hydrolysed 
by aqueous NaOH and why? [1] 
 
4. Write the IUPAC name of the following: [1] 
3
33
25
          CH
           |
CH  C  CH CH
           |      |
           C H OH
? ? ?  
 
5. CO (g) and H2 (g) react to give different products in the presence of different 
catalysts. Which ability of the catalyst is shown by these reactions? [1] 
 
6. Among the hydrides of Group-15 elements, which have the [2] 
(a) Lowest boiling point? 
(b) Maximum basic character? 
(c) Highest bond angle? 
(d) Maximum reducing character? 
 
7. Calculate the freezing point of a solution containing 60 g of glucose (Molar 
mass = 180g mol
-1
) in 250 g of water. (Kf of water = 1.86 K kg mol
-1
) [2] 
 
 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
8. How do you convert the following? [2] 
(a) Ethanal to Propanone 
(b) Toluene to Benzoic acid 
 
OR 
Account for the following: 
(a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction. 
(b) pka value of 4-nitrobenzoic acid is lower than that of benzoic acid. 
 
9. Complete and balance the following chemical equations: [2] 
(a) 
2
4
Fe MnO H
? ? ?
? ? ? 
(b) 
42
MnO H O I
??
? ? ? 
 
10. For the reaction [2] 
2N2O5(g) ? 4NO2(g) + O2 (g) 
The rate of formation of NO2(g) is 2.8 x 10
-3
 M s
-1
.  
Calculate the rate of disappearance of N2O5(g). 
 
11.   [3] 
(a) Identify the chiral molecule in the following pair:  
 
 
 
(b) Write the structure of the product when chlorobenzene is treated with 
methyl chloride in the presence of sodium metal and dry ether. 
 
(c) Write the structure of the alkene formed by dehydrohalogenation of 1-
bromo-1-methylcyclohexane with alcoholic KOH. 
 
12. A first order reaction is 50% completed in 40 minutes at 300 K and in 20 
minutes at 320 K. Calculate the activation energy of the reaction.  
(Given: log 2 = 0.3010, log 4 = 0.6021, R = 8.314 JK
-1
 mol
-1
) [3] 
 
13. An element X' (At. mass a 40 g mol
-1
) having f.c.c. structure, has unit cell 
edge length of 400 pm. Calculate the density of ‘X’ and the number of unit 
cells in 4 g of ‘X’. (NA = 6.022 x 10
23
 mol
-1
) [3] 
 
 
 
Page 3


  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
CBSE 
Class XII Chemistry 
Board Paper – 2018 
 
Time: 3 Hours  Total Marks: 70                                                                           
  
General Instructions:    
? Please check this question paper contains 26 questions. 
15 min time has been allotted to read this question paper. 
? The question paper has been distributed at 10.15 am. 
From 10.15 am to 10.30 am, the students will read the question paper only and 
will not write any answer on answer book during this period.                                                                                                                 
 
 
1. Write the coordination number and oxidation state of Platinum in the 
complex [Pt (en)2Cl2]. [1] 
 
2. Analysis shows that FeO has a non-stoichiometric composition with formula 
Fe0-95O. Give reason. [1] 
 
3. Out of chlorobenzene and benzyl chloride, which one gets easily hydrolysed 
by aqueous NaOH and why? [1] 
 
4. Write the IUPAC name of the following: [1] 
3
33
25
          CH
           |
CH  C  CH CH
           |      |
           C H OH
? ? ?  
 
5. CO (g) and H2 (g) react to give different products in the presence of different 
catalysts. Which ability of the catalyst is shown by these reactions? [1] 
 
6. Among the hydrides of Group-15 elements, which have the [2] 
(a) Lowest boiling point? 
(b) Maximum basic character? 
(c) Highest bond angle? 
(d) Maximum reducing character? 
 
7. Calculate the freezing point of a solution containing 60 g of glucose (Molar 
mass = 180g mol
-1
) in 250 g of water. (Kf of water = 1.86 K kg mol
-1
) [2] 
 
 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
8. How do you convert the following? [2] 
(a) Ethanal to Propanone 
(b) Toluene to Benzoic acid 
 
OR 
Account for the following: 
(a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction. 
(b) pka value of 4-nitrobenzoic acid is lower than that of benzoic acid. 
 
9. Complete and balance the following chemical equations: [2] 
(a) 
2
4
Fe MnO H
? ? ?
? ? ? 
(b) 
42
MnO H O I
??
? ? ? 
 
10. For the reaction [2] 
2N2O5(g) ? 4NO2(g) + O2 (g) 
The rate of formation of NO2(g) is 2.8 x 10
-3
 M s
-1
.  
Calculate the rate of disappearance of N2O5(g). 
 
11.   [3] 
(a) Identify the chiral molecule in the following pair:  
 
 
 
(b) Write the structure of the product when chlorobenzene is treated with 
methyl chloride in the presence of sodium metal and dry ether. 
 
(c) Write the structure of the alkene formed by dehydrohalogenation of 1-
bromo-1-methylcyclohexane with alcoholic KOH. 
 
12. A first order reaction is 50% completed in 40 minutes at 300 K and in 20 
minutes at 320 K. Calculate the activation energy of the reaction.  
(Given: log 2 = 0.3010, log 4 = 0.6021, R = 8.314 JK
-1
 mol
-1
) [3] 
 
13. An element X' (At. mass a 40 g mol
-1
) having f.c.c. structure, has unit cell 
edge length of 400 pm. Calculate the density of ‘X’ and the number of unit 
cells in 4 g of ‘X’. (NA = 6.022 x 10
23
 mol
-1
) [3] 
 
 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
14. Give reasons for the following: [3] 
(a) Measurement of osmotic pressure method is preferred for the 
determination of molar masses of macromolecules such as proteins and 
polymers. 
(b) Aquatic animals are more comfortable in cold water than in warm water. 
(c) Elevation of boiling point of 1 M KCl solution is nearly double than that 
of 1 M sugar solution. 
 
15. What happens when [3] 
(a) a freshly prepared precipitate of Fe(OH)3 is shaken with a small amount 
of FeCl3 solution? 
(b) persistent dialysis of a colloidal solution is carried out? 
(c) an emulsion is centrifuged? 
 
16. Write the chemical reactions involved in the process of extraction of Gold. 
Explain the role of dilute NaCN and Zn in this process. [3] 
 
17. (A), (B) and (C) are three non-cyclic functional isomers of a carbonyl 
compound with molecular formula C4H8O. Isomers (A) and (C) give positive 
Tollens' test whereas isomer (B) does not give Tollens test but gives 
positive Iodoform test. Isomers (A) and (B) on reduction with Zn(Hg)/conc. 
HCl give the same product (D). 
(a) Write the structures of (A), (B), (C) and (C). 
(b) Out of (A), (B) and (C) isomers, which one is least reactive towards 
addition of HCN? [3] 
 
18.   [3] 
(a) Why is bithional added to soap? 
(b) What is tincture of iodine? Write its one use. 
(c) Among the following, which one acts as a food preservative? Aspartame, 
Aspirin, Sodium Benzoate, Paracetamol 
 
19.   [3] 
(a) Write the formula of the following coordination compound : iron(III) 
hexacyanoferrate(II) 
(b) What type of isomerism is exhibited by the complex (Co (NH3)5Cl)SO4? 
(c) Write the hybridisation and number of unpaired electrons in the complex 
[CoF6]
3-
. (Atomic No. of Co = 27) 
 
20. Define the following with an example of each: [3] 
(a) Polysaccharides 
(b) Denatured protein 
(c) Essential amino acids  
 
OR 
Page 4


  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
CBSE 
Class XII Chemistry 
Board Paper – 2018 
 
Time: 3 Hours  Total Marks: 70                                                                           
  
General Instructions:    
? Please check this question paper contains 26 questions. 
15 min time has been allotted to read this question paper. 
? The question paper has been distributed at 10.15 am. 
From 10.15 am to 10.30 am, the students will read the question paper only and 
will not write any answer on answer book during this period.                                                                                                                 
 
 
1. Write the coordination number and oxidation state of Platinum in the 
complex [Pt (en)2Cl2]. [1] 
 
2. Analysis shows that FeO has a non-stoichiometric composition with formula 
Fe0-95O. Give reason. [1] 
 
3. Out of chlorobenzene and benzyl chloride, which one gets easily hydrolysed 
by aqueous NaOH and why? [1] 
 
4. Write the IUPAC name of the following: [1] 
3
33
25
          CH
           |
CH  C  CH CH
           |      |
           C H OH
? ? ?  
 
5. CO (g) and H2 (g) react to give different products in the presence of different 
catalysts. Which ability of the catalyst is shown by these reactions? [1] 
 
6. Among the hydrides of Group-15 elements, which have the [2] 
(a) Lowest boiling point? 
(b) Maximum basic character? 
(c) Highest bond angle? 
(d) Maximum reducing character? 
 
7. Calculate the freezing point of a solution containing 60 g of glucose (Molar 
mass = 180g mol
-1
) in 250 g of water. (Kf of water = 1.86 K kg mol
-1
) [2] 
 
 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
8. How do you convert the following? [2] 
(a) Ethanal to Propanone 
(b) Toluene to Benzoic acid 
 
OR 
Account for the following: 
(a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction. 
(b) pka value of 4-nitrobenzoic acid is lower than that of benzoic acid. 
 
9. Complete and balance the following chemical equations: [2] 
(a) 
2
4
Fe MnO H
? ? ?
? ? ? 
(b) 
42
MnO H O I
??
? ? ? 
 
10. For the reaction [2] 
2N2O5(g) ? 4NO2(g) + O2 (g) 
The rate of formation of NO2(g) is 2.8 x 10
-3
 M s
-1
.  
Calculate the rate of disappearance of N2O5(g). 
 
11.   [3] 
(a) Identify the chiral molecule in the following pair:  
 
 
 
(b) Write the structure of the product when chlorobenzene is treated with 
methyl chloride in the presence of sodium metal and dry ether. 
 
(c) Write the structure of the alkene formed by dehydrohalogenation of 1-
bromo-1-methylcyclohexane with alcoholic KOH. 
 
12. A first order reaction is 50% completed in 40 minutes at 300 K and in 20 
minutes at 320 K. Calculate the activation energy of the reaction.  
(Given: log 2 = 0.3010, log 4 = 0.6021, R = 8.314 JK
-1
 mol
-1
) [3] 
 
13. An element X' (At. mass a 40 g mol
-1
) having f.c.c. structure, has unit cell 
edge length of 400 pm. Calculate the density of ‘X’ and the number of unit 
cells in 4 g of ‘X’. (NA = 6.022 x 10
23
 mol
-1
) [3] 
 
 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
14. Give reasons for the following: [3] 
(a) Measurement of osmotic pressure method is preferred for the 
determination of molar masses of macromolecules such as proteins and 
polymers. 
(b) Aquatic animals are more comfortable in cold water than in warm water. 
(c) Elevation of boiling point of 1 M KCl solution is nearly double than that 
of 1 M sugar solution. 
 
15. What happens when [3] 
(a) a freshly prepared precipitate of Fe(OH)3 is shaken with a small amount 
of FeCl3 solution? 
(b) persistent dialysis of a colloidal solution is carried out? 
(c) an emulsion is centrifuged? 
 
16. Write the chemical reactions involved in the process of extraction of Gold. 
Explain the role of dilute NaCN and Zn in this process. [3] 
 
17. (A), (B) and (C) are three non-cyclic functional isomers of a carbonyl 
compound with molecular formula C4H8O. Isomers (A) and (C) give positive 
Tollens' test whereas isomer (B) does not give Tollens test but gives 
positive Iodoform test. Isomers (A) and (B) on reduction with Zn(Hg)/conc. 
HCl give the same product (D). 
(a) Write the structures of (A), (B), (C) and (C). 
(b) Out of (A), (B) and (C) isomers, which one is least reactive towards 
addition of HCN? [3] 
 
18.   [3] 
(a) Why is bithional added to soap? 
(b) What is tincture of iodine? Write its one use. 
(c) Among the following, which one acts as a food preservative? Aspartame, 
Aspirin, Sodium Benzoate, Paracetamol 
 
19.   [3] 
(a) Write the formula of the following coordination compound : iron(III) 
hexacyanoferrate(II) 
(b) What type of isomerism is exhibited by the complex (Co (NH3)5Cl)SO4? 
(c) Write the hybridisation and number of unpaired electrons in the complex 
[CoF6]
3-
. (Atomic No. of Co = 27) 
 
20. Define the following with an example of each: [3] 
(a) Polysaccharides 
(b) Denatured protein 
(c) Essential amino acids  
 
OR 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
(a) Write the product when 0-glucose reacts with con. HNO3.  
(b) Amino acids show amphoteric behaviour. Why? 
(c) Write one difference between a-helix and 0-pleated structures of 
proteins. 
 
21. Write the structures of the main products in the following reactions: [3] 
(i)  
     
(ii)  
 
(iii)  
 
 
22. Give reasons [3] 
(a) E
0
 value for Mn
3+
/Mn
2+
 couple is much more positive than that for 
Fe
3+
/Fe
2+
. 
(b) Iron has higher enthalpy of atomization than that of copper. 
(c) Sc
3+
 is colourless in aqueous solution whereas Ti
3+
 is coloured. 
 
23. Shyam went to a grocery shop to purchase some food items. The 
shopkeeper packed all the items in polythene bags and gave them to 
Shyam. But Shyam refused to accept the polythene bags and asked the 
shopkeeper to pack the items in paper bags. He informed the shopkeeper 
about the heavy penalty imposed by the government for using polythene 
bags. The shopkeeper promised that he would use paper bags in future in 
place of polythene bags. [4] 
Answer the following: 
(a) Write the values (at least two) shown by Shyam. 
(b) Write one structural difference between low-density polythene and high-
density polythene. 
(c) Why did Shyam refuse to accept the items in polythene bags? 
(d) What is a biodegradable polymer? Give an example. 
 
Page 5


  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
CBSE 
Class XII Chemistry 
Board Paper – 2018 
 
Time: 3 Hours  Total Marks: 70                                                                           
  
General Instructions:    
? Please check this question paper contains 26 questions. 
15 min time has been allotted to read this question paper. 
? The question paper has been distributed at 10.15 am. 
From 10.15 am to 10.30 am, the students will read the question paper only and 
will not write any answer on answer book during this period.                                                                                                                 
 
 
1. Write the coordination number and oxidation state of Platinum in the 
complex [Pt (en)2Cl2]. [1] 
 
2. Analysis shows that FeO has a non-stoichiometric composition with formula 
Fe0-95O. Give reason. [1] 
 
3. Out of chlorobenzene and benzyl chloride, which one gets easily hydrolysed 
by aqueous NaOH and why? [1] 
 
4. Write the IUPAC name of the following: [1] 
3
33
25
          CH
           |
CH  C  CH CH
           |      |
           C H OH
? ? ?  
 
5. CO (g) and H2 (g) react to give different products in the presence of different 
catalysts. Which ability of the catalyst is shown by these reactions? [1] 
 
6. Among the hydrides of Group-15 elements, which have the [2] 
(a) Lowest boiling point? 
(b) Maximum basic character? 
(c) Highest bond angle? 
(d) Maximum reducing character? 
 
7. Calculate the freezing point of a solution containing 60 g of glucose (Molar 
mass = 180g mol
-1
) in 250 g of water. (Kf of water = 1.86 K kg mol
-1
) [2] 
 
 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
8. How do you convert the following? [2] 
(a) Ethanal to Propanone 
(b) Toluene to Benzoic acid 
 
OR 
Account for the following: 
(a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction. 
(b) pka value of 4-nitrobenzoic acid is lower than that of benzoic acid. 
 
9. Complete and balance the following chemical equations: [2] 
(a) 
2
4
Fe MnO H
? ? ?
? ? ? 
(b) 
42
MnO H O I
??
? ? ? 
 
10. For the reaction [2] 
2N2O5(g) ? 4NO2(g) + O2 (g) 
The rate of formation of NO2(g) is 2.8 x 10
-3
 M s
-1
.  
Calculate the rate of disappearance of N2O5(g). 
 
11.   [3] 
(a) Identify the chiral molecule in the following pair:  
 
 
 
(b) Write the structure of the product when chlorobenzene is treated with 
methyl chloride in the presence of sodium metal and dry ether. 
 
(c) Write the structure of the alkene formed by dehydrohalogenation of 1-
bromo-1-methylcyclohexane with alcoholic KOH. 
 
12. A first order reaction is 50% completed in 40 minutes at 300 K and in 20 
minutes at 320 K. Calculate the activation energy of the reaction.  
(Given: log 2 = 0.3010, log 4 = 0.6021, R = 8.314 JK
-1
 mol
-1
) [3] 
 
13. An element X' (At. mass a 40 g mol
-1
) having f.c.c. structure, has unit cell 
edge length of 400 pm. Calculate the density of ‘X’ and the number of unit 
cells in 4 g of ‘X’. (NA = 6.022 x 10
23
 mol
-1
) [3] 
 
 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
14. Give reasons for the following: [3] 
(a) Measurement of osmotic pressure method is preferred for the 
determination of molar masses of macromolecules such as proteins and 
polymers. 
(b) Aquatic animals are more comfortable in cold water than in warm water. 
(c) Elevation of boiling point of 1 M KCl solution is nearly double than that 
of 1 M sugar solution. 
 
15. What happens when [3] 
(a) a freshly prepared precipitate of Fe(OH)3 is shaken with a small amount 
of FeCl3 solution? 
(b) persistent dialysis of a colloidal solution is carried out? 
(c) an emulsion is centrifuged? 
 
16. Write the chemical reactions involved in the process of extraction of Gold. 
Explain the role of dilute NaCN and Zn in this process. [3] 
 
17. (A), (B) and (C) are three non-cyclic functional isomers of a carbonyl 
compound with molecular formula C4H8O. Isomers (A) and (C) give positive 
Tollens' test whereas isomer (B) does not give Tollens test but gives 
positive Iodoform test. Isomers (A) and (B) on reduction with Zn(Hg)/conc. 
HCl give the same product (D). 
(a) Write the structures of (A), (B), (C) and (C). 
(b) Out of (A), (B) and (C) isomers, which one is least reactive towards 
addition of HCN? [3] 
 
18.   [3] 
(a) Why is bithional added to soap? 
(b) What is tincture of iodine? Write its one use. 
(c) Among the following, which one acts as a food preservative? Aspartame, 
Aspirin, Sodium Benzoate, Paracetamol 
 
19.   [3] 
(a) Write the formula of the following coordination compound : iron(III) 
hexacyanoferrate(II) 
(b) What type of isomerism is exhibited by the complex (Co (NH3)5Cl)SO4? 
(c) Write the hybridisation and number of unpaired electrons in the complex 
[CoF6]
3-
. (Atomic No. of Co = 27) 
 
20. Define the following with an example of each: [3] 
(a) Polysaccharides 
(b) Denatured protein 
(c) Essential amino acids  
 
OR 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
(a) Write the product when 0-glucose reacts with con. HNO3.  
(b) Amino acids show amphoteric behaviour. Why? 
(c) Write one difference between a-helix and 0-pleated structures of 
proteins. 
 
21. Write the structures of the main products in the following reactions: [3] 
(i)  
     
(ii)  
 
(iii)  
 
 
22. Give reasons [3] 
(a) E
0
 value for Mn
3+
/Mn
2+
 couple is much more positive than that for 
Fe
3+
/Fe
2+
. 
(b) Iron has higher enthalpy of atomization than that of copper. 
(c) Sc
3+
 is colourless in aqueous solution whereas Ti
3+
 is coloured. 
 
23. Shyam went to a grocery shop to purchase some food items. The 
shopkeeper packed all the items in polythene bags and gave them to 
Shyam. But Shyam refused to accept the polythene bags and asked the 
shopkeeper to pack the items in paper bags. He informed the shopkeeper 
about the heavy penalty imposed by the government for using polythene 
bags. The shopkeeper promised that he would use paper bags in future in 
place of polythene bags. [4] 
Answer the following: 
(a) Write the values (at least two) shown by Shyam. 
(b) Write one structural difference between low-density polythene and high-
density polythene. 
(c) Why did Shyam refuse to accept the items in polythene bags? 
(d) What is a biodegradable polymer? Give an example. 
 
  
 
CBSE XII  | CHEMISTRY 
Board Paper – 2018 
 
     
24.  [5] 
(a) Write the reactions involved in the following:  
(i) Hofmann bromamide degradation reaction 
(ii) Diazotisation 
(iii) Gabriel phthalimide synthesis 
 
(b) Give reasons  
(i) (CH3)2NH is more basic than (CH2)3N in an aqueous solution. 
(ii) Aromatic diazonium Salts are more stable than aliphatic diazonium 
salts. 
OR 
 
(a) Write the annums of the main products of the following reactions: [5] 
(i)  
 
(ii)  
 
 
 
(iii)  
 
 
(b) Give a simple chemical test to distinguish between Aniline and N,N-
dimethylaniline.  
 
(c) Arrange the following in the increasing order of their pkb values: 
C6H5NH2, C2H5NH2, C6H3NHCH3 
25.   [5] 
(a) Give reasons: 
(i) H3PO3 undergoes disproportionation reaction but H3PO4 does not. 
(ii) When Cl2 reacts with excess of F2, ClF3 is formed and not FCl3. 
(iii) Dioxygen is a gas while Sulphur is a solid at room temperature. 
 
(b) Draw the structures of the following: 
(i) XeF4  
(ii) HClO3 
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