ICSE Chemistry Sample Paper with Solution - 2025 | ICSE Class 12 Science Sample Papers PDF Download

 Page 1


 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
1 
 
CHEMISTRY 
PAPER 1  
(THEORY) 
 
Maximum Marks: 70 
Time Allotted: Three Hours 
Reading Time: Additional Fifteen minutes 
 
Instructions to Candidates 
? You are allowed additional 15 minutes for only reading the question 
paper. 
? You must NOT start writing during the reading time. 
? This question paper has 11 printed pages.   
? It is divided into four sections and has 21 questions in all. 
? All questions are compulsory. Answer all questions. 
? Section A has fourteen subparts. Each question carries 1 mark. 
? While attempting Multiple Choice Questions in Section A, you are 
required to write only ONE option as the answer. 
? Section B has ten questions. Each question carries 2 marks. 
? Section C has seven questions. Each question carries 3 marks. 
? Section D has three questions. Each question carries 5 marks. 
? Internal choices have been provided in one question each in Sections B, 
C and D. 
? The intended marks for questions are given in brackets [ ]. 
? All working, including rough work, should be done on the same sheet as, 
and adjacent to the rest of the answer. 
? Balanced equations must be given wherever possible and diagrams where 
they are helpful. 
? When solving numerical problems, all essential workings must be shown. 
? In working out problems, use the following data:  
Gas constant R=1·987cal deg
-1
mol
-1
=8·314JK
-1
mol
-1                          
=0·0821dm
3
atmK
-1
mol
-1
, 1 l atm =1dm
3
atm=101·3 J.                                          
1 Faraday=96500 coulombs. Avogadro’s number= 6·023×10
23
. 
 
Instruction to Supervising Examiner 
? Kindly read aloud the Instructions given above to all the candidates present 
in the examination hall. 
Page 2


 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
1 
 
CHEMISTRY 
PAPER 1  
(THEORY) 
 
Maximum Marks: 70 
Time Allotted: Three Hours 
Reading Time: Additional Fifteen minutes 
 
Instructions to Candidates 
? You are allowed additional 15 minutes for only reading the question 
paper. 
? You must NOT start writing during the reading time. 
? This question paper has 11 printed pages.   
? It is divided into four sections and has 21 questions in all. 
? All questions are compulsory. Answer all questions. 
? Section A has fourteen subparts. Each question carries 1 mark. 
? While attempting Multiple Choice Questions in Section A, you are 
required to write only ONE option as the answer. 
? Section B has ten questions. Each question carries 2 marks. 
? Section C has seven questions. Each question carries 3 marks. 
? Section D has three questions. Each question carries 5 marks. 
? Internal choices have been provided in one question each in Sections B, 
C and D. 
? The intended marks for questions are given in brackets [ ]. 
? All working, including rough work, should be done on the same sheet as, 
and adjacent to the rest of the answer. 
? Balanced equations must be given wherever possible and diagrams where 
they are helpful. 
? When solving numerical problems, all essential workings must be shown. 
? In working out problems, use the following data:  
Gas constant R=1·987cal deg
-1
mol
-1
=8·314JK
-1
mol
-1                          
=0·0821dm
3
atmK
-1
mol
-1
, 1 l atm =1dm
3
atm=101·3 J.                                          
1 Faraday=96500 coulombs. Avogadro’s number= 6·023×10
23
. 
 
Instruction to Supervising Examiner 
? Kindly read aloud the Instructions given above to all the candidates present 
in the examination hall. 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
2 
SECTION A - 14 MARKS 
Question 1   
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the 
brackets: 
[four, three, remains same, propane, ns
1-2
, increases, six, propan-2-ol,                                 
(n-1)d
1-10
, two, decreases, Clemmensen’s, Wolff-Kishner] 
[4×1] 
 (i) The molar conductance of a solution _________ on dilution but the 
specific conductance of a solution  _________ on dilution.                        
(Understanding) 
 
 (ii) In the complex ion [CoCl(en)2ONO]
+
, the coordination number and 
the oxidation number of the central metal ion are ______ and 
________.                                                                  (Understanding) 
 
 (iii) Propanone on reaction with zinc amalgam in the presence of 
concentrated HCl gives ______ and the reaction is called _______ 
reduction.                                                                                 (Recall) 
 
 (iv) The variation and magnitude of oxidation state in coordination 
complexes is due to the participation of inner ________ electrons in 
addition to outer __________ electrons.                   (Understanding) 
 
(B) Select and write the correct alternative from the choices given below. [7×1] 
 (i) The correct order of the increasing basic nature of Ammonia, 
Methylamine and Aniline is:                                                  (Analysis) 
 
  (a) Methylamine < Aniline < Ammonia 
 
  (b) Aniline < Methylamine < Ammonia 
 
  (c) Ammonia < Aniline < Methylamine  
 
  (d) Aniline < Ammonia < Methylamine                                   
 
 (ii) Colligative properties of a solution are:                    (Understanding) 
 
  (P) Independent of the nature of solute 
 
  (Q) Proportional to molecular mass of solute 
 
  (R) Proportional to concentration of solute 
 
  (S) Independent of the amount of solvent 
 
   (a) Only P and Q are correct  
 
   (b) Only P and R are correct 
 
   (c) Only P and S are correct 
 
 
 
 (d) Only Q and S are correct        
 
 
Page 3


 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
1 
 
CHEMISTRY 
PAPER 1  
(THEORY) 
 
Maximum Marks: 70 
Time Allotted: Three Hours 
Reading Time: Additional Fifteen minutes 
 
Instructions to Candidates 
? You are allowed additional 15 minutes for only reading the question 
paper. 
? You must NOT start writing during the reading time. 
? This question paper has 11 printed pages.   
? It is divided into four sections and has 21 questions in all. 
? All questions are compulsory. Answer all questions. 
? Section A has fourteen subparts. Each question carries 1 mark. 
? While attempting Multiple Choice Questions in Section A, you are 
required to write only ONE option as the answer. 
? Section B has ten questions. Each question carries 2 marks. 
? Section C has seven questions. Each question carries 3 marks. 
? Section D has three questions. Each question carries 5 marks. 
? Internal choices have been provided in one question each in Sections B, 
C and D. 
? The intended marks for questions are given in brackets [ ]. 
? All working, including rough work, should be done on the same sheet as, 
and adjacent to the rest of the answer. 
? Balanced equations must be given wherever possible and diagrams where 
they are helpful. 
? When solving numerical problems, all essential workings must be shown. 
? In working out problems, use the following data:  
Gas constant R=1·987cal deg
-1
mol
-1
=8·314JK
-1
mol
-1                          
=0·0821dm
3
atmK
-1
mol
-1
, 1 l atm =1dm
3
atm=101·3 J.                                          
1 Faraday=96500 coulombs. Avogadro’s number= 6·023×10
23
. 
 
Instruction to Supervising Examiner 
? Kindly read aloud the Instructions given above to all the candidates present 
in the examination hall. 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
2 
SECTION A - 14 MARKS 
Question 1   
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the 
brackets: 
[four, three, remains same, propane, ns
1-2
, increases, six, propan-2-ol,                                 
(n-1)d
1-10
, two, decreases, Clemmensen’s, Wolff-Kishner] 
[4×1] 
 (i) The molar conductance of a solution _________ on dilution but the 
specific conductance of a solution  _________ on dilution.                        
(Understanding) 
 
 (ii) In the complex ion [CoCl(en)2ONO]
+
, the coordination number and 
the oxidation number of the central metal ion are ______ and 
________.                                                                  (Understanding) 
 
 (iii) Propanone on reaction with zinc amalgam in the presence of 
concentrated HCl gives ______ and the reaction is called _______ 
reduction.                                                                                 (Recall) 
 
 (iv) The variation and magnitude of oxidation state in coordination 
complexes is due to the participation of inner ________ electrons in 
addition to outer __________ electrons.                   (Understanding) 
 
(B) Select and write the correct alternative from the choices given below. [7×1] 
 (i) The correct order of the increasing basic nature of Ammonia, 
Methylamine and Aniline is:                                                  (Analysis) 
 
  (a) Methylamine < Aniline < Ammonia 
 
  (b) Aniline < Methylamine < Ammonia 
 
  (c) Ammonia < Aniline < Methylamine  
 
  (d) Aniline < Ammonia < Methylamine                                   
 
 (ii) Colligative properties of a solution are:                    (Understanding) 
 
  (P) Independent of the nature of solute 
 
  (Q) Proportional to molecular mass of solute 
 
  (R) Proportional to concentration of solute 
 
  (S) Independent of the amount of solvent 
 
   (a) Only P and Q are correct  
 
   (b) Only P and R are correct 
 
   (c) Only P and S are correct 
 
 
 
 (d) Only Q and S are correct        
 
 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
3 
(iii) According to Markownikoff’s rule, “The negative part of the halogen acid 
attaches itself with that C atom of an unsymmetrical alkene which has least 
number of H-atom.”  
Anti-Markownikoff’s addition of HBr is NOT observed in:          (Analysis) 
 
 (a) Propene   
 (b) But-2-ene   
 (c) But-1-ene  
 (d) Pent-2-ene                                                           
(iv) 
Most of the naturally occurring a-amino acids are optically active and have                     
L-configuration. Which of the following amino acids is NOT asymmetric? 
(Recall) 
 
 (a) Valine  
 (b) Alanine  
 (c) Glycine  
 (d) Leucine   
(v) Which one of the following complex ions has geometrical isomers?  
(Understanding) 
 
 (a) [Ni(NH3)5Br]
+
  
 (b) [Cr(NH3)4en]
3+
  
 (c) [Co(NH3)2(en)2]
3+
  
 (d) [Co(NH3)6]
3+                                                                                               
  
(vi) Given below are two statements marked Assertion and Reason. Read the two 
statements carefully and select the correct option. 
Assertion: Tertiary butyl bromide undergoes Wurtz reaction to give 2,2,3,3 
tetramethyl butane.  
Reason: In Wurtz reaction, when same alkyl halides react with sodium in dry 
ether to give hydrocarbon; the hydrocarbon formed contains double 
the number of carbon atoms present in the alkyl halide.             
(Analysis) 
 
 (a) Both Assertion and Reason are true and Reason is the correct 
explanation of assertion. 
 
 (b) Both Assertion and Reason are true but Reason is not the correct 
explanation for Assertion. 
 
 (c) Assertion is true but Reason is false.  
 (d) Both Assertion and Reason are false.    
 
 
Page 4


 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
1 
 
CHEMISTRY 
PAPER 1  
(THEORY) 
 
Maximum Marks: 70 
Time Allotted: Three Hours 
Reading Time: Additional Fifteen minutes 
 
Instructions to Candidates 
? You are allowed additional 15 minutes for only reading the question 
paper. 
? You must NOT start writing during the reading time. 
? This question paper has 11 printed pages.   
? It is divided into four sections and has 21 questions in all. 
? All questions are compulsory. Answer all questions. 
? Section A has fourteen subparts. Each question carries 1 mark. 
? While attempting Multiple Choice Questions in Section A, you are 
required to write only ONE option as the answer. 
? Section B has ten questions. Each question carries 2 marks. 
? Section C has seven questions. Each question carries 3 marks. 
? Section D has three questions. Each question carries 5 marks. 
? Internal choices have been provided in one question each in Sections B, 
C and D. 
? The intended marks for questions are given in brackets [ ]. 
? All working, including rough work, should be done on the same sheet as, 
and adjacent to the rest of the answer. 
? Balanced equations must be given wherever possible and diagrams where 
they are helpful. 
? When solving numerical problems, all essential workings must be shown. 
? In working out problems, use the following data:  
Gas constant R=1·987cal deg
-1
mol
-1
=8·314JK
-1
mol
-1                          
=0·0821dm
3
atmK
-1
mol
-1
, 1 l atm =1dm
3
atm=101·3 J.                                          
1 Faraday=96500 coulombs. Avogadro’s number= 6·023×10
23
. 
 
Instruction to Supervising Examiner 
? Kindly read aloud the Instructions given above to all the candidates present 
in the examination hall. 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
2 
SECTION A - 14 MARKS 
Question 1   
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the 
brackets: 
[four, three, remains same, propane, ns
1-2
, increases, six, propan-2-ol,                                 
(n-1)d
1-10
, two, decreases, Clemmensen’s, Wolff-Kishner] 
[4×1] 
 (i) The molar conductance of a solution _________ on dilution but the 
specific conductance of a solution  _________ on dilution.                        
(Understanding) 
 
 (ii) In the complex ion [CoCl(en)2ONO]
+
, the coordination number and 
the oxidation number of the central metal ion are ______ and 
________.                                                                  (Understanding) 
 
 (iii) Propanone on reaction with zinc amalgam in the presence of 
concentrated HCl gives ______ and the reaction is called _______ 
reduction.                                                                                 (Recall) 
 
 (iv) The variation and magnitude of oxidation state in coordination 
complexes is due to the participation of inner ________ electrons in 
addition to outer __________ electrons.                   (Understanding) 
 
(B) Select and write the correct alternative from the choices given below. [7×1] 
 (i) The correct order of the increasing basic nature of Ammonia, 
Methylamine and Aniline is:                                                  (Analysis) 
 
  (a) Methylamine < Aniline < Ammonia 
 
  (b) Aniline < Methylamine < Ammonia 
 
  (c) Ammonia < Aniline < Methylamine  
 
  (d) Aniline < Ammonia < Methylamine                                   
 
 (ii) Colligative properties of a solution are:                    (Understanding) 
 
  (P) Independent of the nature of solute 
 
  (Q) Proportional to molecular mass of solute 
 
  (R) Proportional to concentration of solute 
 
  (S) Independent of the amount of solvent 
 
   (a) Only P and Q are correct  
 
   (b) Only P and R are correct 
 
   (c) Only P and S are correct 
 
 
 
 (d) Only Q and S are correct        
 
 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
3 
(iii) According to Markownikoff’s rule, “The negative part of the halogen acid 
attaches itself with that C atom of an unsymmetrical alkene which has least 
number of H-atom.”  
Anti-Markownikoff’s addition of HBr is NOT observed in:          (Analysis) 
 
 (a) Propene   
 (b) But-2-ene   
 (c) But-1-ene  
 (d) Pent-2-ene                                                           
(iv) 
Most of the naturally occurring a-amino acids are optically active and have                     
L-configuration. Which of the following amino acids is NOT asymmetric? 
(Recall) 
 
 (a) Valine  
 (b) Alanine  
 (c) Glycine  
 (d) Leucine   
(v) Which one of the following complex ions has geometrical isomers?  
(Understanding) 
 
 (a) [Ni(NH3)5Br]
+
  
 (b) [Cr(NH3)4en]
3+
  
 (c) [Co(NH3)2(en)2]
3+
  
 (d) [Co(NH3)6]
3+                                                                                               
  
(vi) Given below are two statements marked Assertion and Reason. Read the two 
statements carefully and select the correct option. 
Assertion: Tertiary butyl bromide undergoes Wurtz reaction to give 2,2,3,3 
tetramethyl butane.  
Reason: In Wurtz reaction, when same alkyl halides react with sodium in dry 
ether to give hydrocarbon; the hydrocarbon formed contains double 
the number of carbon atoms present in the alkyl halide.             
(Analysis) 
 
 (a) Both Assertion and Reason are true and Reason is the correct 
explanation of assertion. 
 
 (b) Both Assertion and Reason are true but Reason is not the correct 
explanation for Assertion. 
 
 (c) Assertion is true but Reason is false.  
 (d) Both Assertion and Reason are false.    
 
 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
4 
(vii) Given below are two statements marked Assertion and Reason. Read the two 
statements carefully and select the correct option. 
Assertion: There is a continuous increase in size among Lanthanoids with an 
increase in atomic number.  
Reason: Lanthanoids do not show Lanthanoid contraction.            (Analysis)  
 
 (a) Both Assertion and Reason are true and Reason is the correct 
explanation of Assertion. 
 
 (b) Both Assertion and Reason are true but Reason is not the correct 
explanation for assertion. 
 
 (c) Assertion is true but Reason is false.  
 (d) Both Assertion and Reason are false.                     
(C) Read the passage carefully and answer the questions that follow. [3×1] 
 
A plant or any other living being maintains a reasonable balance of C-14 
(radioactive carbon) in its tissue during its lifetime. C-14 is used to determine 
the age of fossils. In the upper atmosphere, neutrons present in the cosmic 
rays are captured to produce the following nuclear reaction. 
               7N
14
  +  0n
1                   
6C
14
    +  1H
1
 
C-14 isotope is circulated in the atmosphere and gets absorbed by living 
organism during photosynthesis. The ratio of C-14 to C-12 in living being is 
1:10
12
. Once the living being dies, the level of C-14 in the dead being 
decreases due to the following reaction. 
                                          6C
14                    
7N
14
  +  -1e
0
   +  ? rays 
The death of the plant brings an end to its tendency to take up C-14. The half-
life period of C-14 is 5770 years. By knowing the concentration of C-14 in 
the living plant and the piece of dead material at a particular time, the age of 
the material (fossil) can be determined.  
 
 (i) 
Write the relation between the decay constant and half-life period.         
(Recall) 
 
 (ii) In a piece of dead wood, the activity or concentration of C-14 is found 
to be one third of its initial activity. Calculate the age of the old wood.                                                                           
(Application) 
 
 (iii) The half-life period (t1/2) for a first order reaction is 30 minutes. 
Calculate the time taken to complete 87·5% of the reaction.                                            
(Application) 
 
 
 
 
 
Page 5


 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
1 
 
CHEMISTRY 
PAPER 1  
(THEORY) 
 
Maximum Marks: 70 
Time Allotted: Three Hours 
Reading Time: Additional Fifteen minutes 
 
Instructions to Candidates 
? You are allowed additional 15 minutes for only reading the question 
paper. 
? You must NOT start writing during the reading time. 
? This question paper has 11 printed pages.   
? It is divided into four sections and has 21 questions in all. 
? All questions are compulsory. Answer all questions. 
? Section A has fourteen subparts. Each question carries 1 mark. 
? While attempting Multiple Choice Questions in Section A, you are 
required to write only ONE option as the answer. 
? Section B has ten questions. Each question carries 2 marks. 
? Section C has seven questions. Each question carries 3 marks. 
? Section D has three questions. Each question carries 5 marks. 
? Internal choices have been provided in one question each in Sections B, 
C and D. 
? The intended marks for questions are given in brackets [ ]. 
? All working, including rough work, should be done on the same sheet as, 
and adjacent to the rest of the answer. 
? Balanced equations must be given wherever possible and diagrams where 
they are helpful. 
? When solving numerical problems, all essential workings must be shown. 
? In working out problems, use the following data:  
Gas constant R=1·987cal deg
-1
mol
-1
=8·314JK
-1
mol
-1                          
=0·0821dm
3
atmK
-1
mol
-1
, 1 l atm =1dm
3
atm=101·3 J.                                          
1 Faraday=96500 coulombs. Avogadro’s number= 6·023×10
23
. 
 
Instruction to Supervising Examiner 
? Kindly read aloud the Instructions given above to all the candidates present 
in the examination hall. 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
2 
SECTION A - 14 MARKS 
Question 1   
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the 
brackets: 
[four, three, remains same, propane, ns
1-2
, increases, six, propan-2-ol,                                 
(n-1)d
1-10
, two, decreases, Clemmensen’s, Wolff-Kishner] 
[4×1] 
 (i) The molar conductance of a solution _________ on dilution but the 
specific conductance of a solution  _________ on dilution.                        
(Understanding) 
 
 (ii) In the complex ion [CoCl(en)2ONO]
+
, the coordination number and 
the oxidation number of the central metal ion are ______ and 
________.                                                                  (Understanding) 
 
 (iii) Propanone on reaction with zinc amalgam in the presence of 
concentrated HCl gives ______ and the reaction is called _______ 
reduction.                                                                                 (Recall) 
 
 (iv) The variation and magnitude of oxidation state in coordination 
complexes is due to the participation of inner ________ electrons in 
addition to outer __________ electrons.                   (Understanding) 
 
(B) Select and write the correct alternative from the choices given below. [7×1] 
 (i) The correct order of the increasing basic nature of Ammonia, 
Methylamine and Aniline is:                                                  (Analysis) 
 
  (a) Methylamine < Aniline < Ammonia 
 
  (b) Aniline < Methylamine < Ammonia 
 
  (c) Ammonia < Aniline < Methylamine  
 
  (d) Aniline < Ammonia < Methylamine                                   
 
 (ii) Colligative properties of a solution are:                    (Understanding) 
 
  (P) Independent of the nature of solute 
 
  (Q) Proportional to molecular mass of solute 
 
  (R) Proportional to concentration of solute 
 
  (S) Independent of the amount of solvent 
 
   (a) Only P and Q are correct  
 
   (b) Only P and R are correct 
 
   (c) Only P and S are correct 
 
 
 
 (d) Only Q and S are correct        
 
 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
3 
(iii) According to Markownikoff’s rule, “The negative part of the halogen acid 
attaches itself with that C atom of an unsymmetrical alkene which has least 
number of H-atom.”  
Anti-Markownikoff’s addition of HBr is NOT observed in:          (Analysis) 
 
 (a) Propene   
 (b) But-2-ene   
 (c) But-1-ene  
 (d) Pent-2-ene                                                           
(iv) 
Most of the naturally occurring a-amino acids are optically active and have                     
L-configuration. Which of the following amino acids is NOT asymmetric? 
(Recall) 
 
 (a) Valine  
 (b) Alanine  
 (c) Glycine  
 (d) Leucine   
(v) Which one of the following complex ions has geometrical isomers?  
(Understanding) 
 
 (a) [Ni(NH3)5Br]
+
  
 (b) [Cr(NH3)4en]
3+
  
 (c) [Co(NH3)2(en)2]
3+
  
 (d) [Co(NH3)6]
3+                                                                                               
  
(vi) Given below are two statements marked Assertion and Reason. Read the two 
statements carefully and select the correct option. 
Assertion: Tertiary butyl bromide undergoes Wurtz reaction to give 2,2,3,3 
tetramethyl butane.  
Reason: In Wurtz reaction, when same alkyl halides react with sodium in dry 
ether to give hydrocarbon; the hydrocarbon formed contains double 
the number of carbon atoms present in the alkyl halide.             
(Analysis) 
 
 (a) Both Assertion and Reason are true and Reason is the correct 
explanation of assertion. 
 
 (b) Both Assertion and Reason are true but Reason is not the correct 
explanation for Assertion. 
 
 (c) Assertion is true but Reason is false.  
 (d) Both Assertion and Reason are false.    
 
 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
4 
(vii) Given below are two statements marked Assertion and Reason. Read the two 
statements carefully and select the correct option. 
Assertion: There is a continuous increase in size among Lanthanoids with an 
increase in atomic number.  
Reason: Lanthanoids do not show Lanthanoid contraction.            (Analysis)  
 
 (a) Both Assertion and Reason are true and Reason is the correct 
explanation of Assertion. 
 
 (b) Both Assertion and Reason are true but Reason is not the correct 
explanation for assertion. 
 
 (c) Assertion is true but Reason is false.  
 (d) Both Assertion and Reason are false.                     
(C) Read the passage carefully and answer the questions that follow. [3×1] 
 
A plant or any other living being maintains a reasonable balance of C-14 
(radioactive carbon) in its tissue during its lifetime. C-14 is used to determine 
the age of fossils. In the upper atmosphere, neutrons present in the cosmic 
rays are captured to produce the following nuclear reaction. 
               7N
14
  +  0n
1                   
6C
14
    +  1H
1
 
C-14 isotope is circulated in the atmosphere and gets absorbed by living 
organism during photosynthesis. The ratio of C-14 to C-12 in living being is 
1:10
12
. Once the living being dies, the level of C-14 in the dead being 
decreases due to the following reaction. 
                                          6C
14                    
7N
14
  +  -1e
0
   +  ? rays 
The death of the plant brings an end to its tendency to take up C-14. The half-
life period of C-14 is 5770 years. By knowing the concentration of C-14 in 
the living plant and the piece of dead material at a particular time, the age of 
the material (fossil) can be determined.  
 
 (i) 
Write the relation between the decay constant and half-life period.         
(Recall) 
 
 (ii) In a piece of dead wood, the activity or concentration of C-14 is found 
to be one third of its initial activity. Calculate the age of the old wood.                                                                           
(Application) 
 
 (iii) The half-life period (t1/2) for a first order reaction is 30 minutes. 
Calculate the time taken to complete 87·5% of the reaction.                                            
(Application) 
 
 
 
 
 
 
---------------------------------------------------------------------------------------------------------------- 
ISC SPECIMEN QUESTION PAPER 2025 
5 
SECTION B – 20 MARKS 
Question 2 [2] 
The solution of two electrolytes A and B are diluted. ^
?? of B increases 1·5 times while 
that of A increases 25 times. Which of the two is a strong electrolyte? Give a reason. 
 (Understanding)                                                  
 
 
 
Question 3 [2] 
An organic compound [A] which has characteristic odour, reacts with conc. NaOH to 
give two compounds [B] and [C]. Compound [B] has molecular formula C7H8O which 
upon oxidation gives back compound [A]. Compound [C] is the sodium salt of the acid 
and upon treatment with sodalime yields an aromatic hydrocarbon [D]. Identify the 
compounds [A], [B], [C] and [D].                                                          (Understanding) 
 
 
 
Question 4 [2] 
Devise a scheme for the synthesis of n-butane using CH3I as the only source of carbon. 
Is it possible to obtain propane in pure state by applying this scheme? Give a reason for 
your answer.                                                                                                     (Evaluate) 
 
 
 
Question 5 [2] 
It is generally observed that the rate of a chemical reaction becomes double with every 
10
o
C rise in temperature. If the generalisation holds true for a reaction in the temperature 
range of 298K to 308K, what would be the value of activation energy (Ea) for the 
reaction?                                                                                                       (Application)               
 
 
 
Question 6                                                                                               [2] 
An organic compound [X] of molecular formula C3H5N, in one reaction produced a 
primary amine with LiAlH4. In another case, the organic compound [Y] of same 
molecular formula C3H5N produced a secondary amine with LiAlH4. Identify both the 
compounds [X] and [Y]. Why do these compounds form two different products?                               
(Understanding) 
 
 
 
Question 7 [2] 
During chemistry class, a teacher wrote [Ni(CN)4]
2- 
as a coordination complex ion on 
the board. The students were asked to find out the magnetic behaviour and shape of the 
complex. Pari, a student, wrote the answer paramagnetic and tetrahedral whereas 
another student Suhail wrote diamagnetic and square planer.  
Evaluate Pari’s and Suhail’s responses.                                                           (Evaluate)