ISC (Science)
Academic Year: 2025-2026
Date & Time: 23rd February 2026, 2:00 pm
Duration: 3h
Advertisements
Instructions to Candidates
- You are allowed an additional fifteen minutes for only reading the question paper.
- You must NOT start writing during the reading time.
- This question paper has 11 printed pages and one blank page.
- It is divided into four sections and has twenty-one questions in all.
- 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 = 1.987 cal deg−1 mol−1 = 8.314 J K−1 mol−1 = 0.0821 dm3
1 atm = 1 dm3 atm = 101.3 J
1 faraday = 96,500 coulombs
Avogadro’s number = 6.023 × 1023
Fill in the blank by choosing the appropriate word from the bracket:
[first, alc. AgCN, primary, decrease, third, increase, zero, Lucas, alc. KCN, KOH, no change, two, Tollen’s, AgOH, tertiary]
A mixture of anhydrous ZnCl2 and conc. HCl is called ______ reagent which shows maximum reactivity with ______ alcohol.
Chapter:
Fill in the blank by choosing the appropriate word from the bracket:
[first, alc. AgCN, primary, decrease, third, increase, zero, Lucas, alc. KCN, KOH, no change, two, Tollen’s, AgOH, tertiary]
Methyl chloride on treatment with ______ forms methyl cyanide, whereas on treatment with ______ it forms methyl isocyanide.
Chapter:
Fill in the blank by choosing the appropriate word from the bracket:
[first, alc. AgCN, primary, decrease, third, increase, zero, Lucas, alc. KCN, KOH, no change, two, Tollen’s, AgOH, tertiary]
The hydrolysis of ethyl acetate in acidic medium is a pseudo ______ order reaction. However, the molecularity of the reaction is ______.
Chapter:
Fill in the blank by choosing the appropriate word from the bracket:
[first, alc. AgCN, primary, decrease, third, increase, zero, Lucas, alc. KCN, KOH, no change, two, Tollen’s, AgOH, tertiary]
Dissociation of solute particles leads to a/an ______ in the magnitude of a colligative property and a/an ______ in the value of the observed molecular mass.
Chapter:
Which one of the following is a tetrahedral complex as well as diamagnetic in nature?
[Ni(CN)4]2−
[NiCl4]2−
[Cu(NH3)4]2−
[Ni(CO)4]
Chapter:
When H2S gas is passed through acidified K2Cr2O7 solution, the colour of the solution changes to ______
green.
orange.
black.
red.
Chapter:
Identify the end product [C] in the following sequence of chemical reaction:
\[\ce{CH ≡ CH ->[dil{.} H2SO4/HgSO4][][A]->[{[O]}][][B]->[PCl5][][C]}\]
Acetic anhydride
Acetic acid
Acetyl chloride
Ethyl chloride
Chapter:
Rohit is studying the iodoform reaction by using the following compounds:
(P) CH3OH
(Q) CH3CHO
(R) CH3COCH3
(S) CH3CH2−CO−CH2−CH3
Which of the following combinations will give an iodoform test when the compounds are heated separately with iodine and aqueous NaOH?
Only (P) and (Q)
Only (Q) and (R)
Only (P) and (S)
Only (Q) and (S)
Chapter:
Which one of the following nitrogen bases is absent in RNA?
Adenine
Guanine
Uracil
Thymine
Chapter:
Assertion: Phenols are more acidic than aliphatic alcohols.
Reason: Phenoxide ion is stabilised by resonance but alkoxide ion is not stabilised by resonance.
Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.
Assertion is true and Reason is false.
Both Assertion and Reason are false.
Chapter:
Assertion: The depression of freezing point of 0.1 molal aqueous solution of MgCl2 is less than that of 0.1 molal aqueous solution of NaCl.
Reason: The number of particles furnished by 0.1 molal MgCl2 is less than that of 0.1 molal NaCl.
Both Assertion and Reason are true, and Reason is the correct explanation for Assertion.
Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion.
Assertion is true and Reason is false.
Both Assertion and Reason are false.
Chapter:
Read the information given below and answer the questions that follow.
|
Kohlrausch observed an interesting pattern between the values of molar conductance at infinite dilution (`Λ_m^∞`) for strong electrolytes. It was observed that different pairs of electrolytes having a common cation or anion had almost same difference of `Λ_m^∞`. On the basis of his observation, he postulated a law known as Kohlrausch’s Law of Independent Migration of ions. The values of molar conductivities at infinite dilution for some cations and anions are as follows:
|
- State the Kohlrausch’s Law of Independent Migration of ions.
- Calculate the molar conductance at infinite dilution `Λ_m^∞` for BaCl2.
- Arrange the values of `Λ_m^∞`, for CaSO4 and BaCl2 in increasing order.
Chapter:
A reaction is first order in A and second order in B. How is the rate affected on increasing the concentration of B three times?
Chapter:
A reaction is first order in A and second order in B. How is the rate affected when the concentrations of both A and B are doubled?
Chapter:
0.680 g of a compound is dissolved in 15.0 g of benzene, and the freezing point of the solution is lowered by 1.44°C.
Calculate the experimental molecular mass of the compound.
(Kf for benzene = 5.12 K kg mol−1)
Chapter:
If the theoretical molecular mass of the compound referred to above is 80.5 g/mol−1, suggest whether it is undergoing association or dissociation.
Chapter:
Write the IUPAC name of the following complex compound:
[Pt(NH3)4Cl2]SO4
Chapter:
Write the IUPAC name of the following complex:
K2[Ni(CN4)]
Chapter:
Write chemical equations to convert the following:
Methyl magnesium bromide to propan-2-ol.
Chapter:
How is phenol converted into the following?
Benzene
Chapter:
Calculate the value of ΔG° for the following cell at 25°C.
\[\ce{Zn_{(s)}/Zn^2+(1M) || Sn^2+(1M)/Sn_{(s)}}\]
Given: \[\ce{E^{\circ}_{({Zn^{2+}/{Zn}})}}\] = −0.76 V, \[\ce{E^{\circ}_{({Sn^{2+}/{Sn}})}}\] = −0.14 V
1 faraday = 96,500 coulombs.
Chapter:
Advertisements
Write chemical reactions for the following named organic reaction:
Diazotisation reaction
Chapter:
Explain the following reaction with a suitable example.
Sandmeyer reaction
Chapter:
A first order reaction is 40% complete in 20 minutes. Calculate the time required for 90% completion of the same reaction.
Chapter:
Write a reaction to distinguish acetaldehyde from acetone.
Chapter:
Write a chemical test to distinguish between the following pair of compounds:
Acetic acid and benzaldehyde
Chapter:
An organic compound [A] having molecular formula C3H8O gives turbidity with Lucas reagent within five minutes of mixing. On heating compound [A] with Cu at 573K, compound [B] is formed. Compound [B] does not reduce Fehling’s solution but when heated with iodine and sodium hydroxide, it gives a yellow precipitate of compound [C]. Identify the compounds [A], [B] and [C].
Write the chemical reaction for the conversion of compound [B] to compound [C].
Chapter:
Why first ionization enthalpy of chromium is lower than that of zinc?
Chapter:
Explain why does colour of KMnO4 disappear when oxalic acid is added to its solution in acidic medium.
Chapter:
How is the following conversion carried out?
Chlorobenzene to aniline.
Chapter:
How will you bring the following conversion?
Iodoform to acetylene
Chapter:
Write a chemical equation to convert the following:
Methanol to ethanol.
Chapter:
How will the following be converted? (Give chemical equation)
Benzene diazonium chloride to phenol.
Chapter:
How will the following be obtained? (Give chemical equation):
Diethyl ether from sodium ethoxide.
Chapter:
Complete and balance the chemical equation:
\[\ce{K2Cr2O7 + H2SO4 + KI →}\] ______ + ______ + ______ + ______
Chapter:
Complete and balance the following reaction:
\[\ce{KMnO4 + H2SO4 + FeSO4 ->}\] ______ + ______ + ______ + ______
Chapter:
Which ion, Co2+ or Zn2+, is attracted to a magnetic field? Give reasons.
(Atomic Number of Co = 27 and Zn = 30)
Chapter:
Give one example each of fibrous protein and globular protein.
Chapter:
The structures of glycine and alanine are given below. Show the peptide bond linkage in glycylalanine.
\[\ce{\underset{Glycine}{H2N - CH2 - COOH}}\];
\[\begin{array}{cc}
\ce{CH3}\phantom{..}\\
|\phantom{.....}\\
\ce{\underset{Alanine}{H2N - CH - COOH}}\
\end{array}\]
Chapter:
Justify that glucose is an aldose form of sugar, with the help of a chemical reaction.
Chapter:
Write the chemical reaction when chlorobenzene is heated with conc. HNO3 in the presence of conc. H2SO4.
Chapter:
Write the chemical reaction when ethyl alcohol is treated with SOCl2 the presence of pyridine.
Chapter:
Write the chemical reaction when chloroform is slowly oxidized with oxygen in the presence of sunlight.
Chapter:
Advertisements
The rate constant of a first order reaction increases five times when the temperature is raised from 350 K to 500 K. Calculate the activation energy of the reaction. (R = 8.314 JK−1 mol−1)
Chapter:
The unit of the rate constant of a reaction is the same as that of its rate of reaction. Find the order of this reaction.
Chapter:
The molar conductivity at infinite dilution for `λ_(H^+)^∞ = 348.65 S cm^2 mol^(−1)` and for `λ_(CH_3COO^-)^∞ = 41.4 S cm^2 mol^(−1)` respectively.
Calculate the degree of dissociation (α) of acetic acid if its molar conductivity `∧_m^c is 40.65 S cm^2 mol^(−1)`.
Chapter:
Compounds [A] and [B] are two electrolytes. Upon dilution, the molar conductivity of compound [A] increases 3 times while that of [B] increases 30 times. Which one of the two is a weak electrolyte? Why?
Chapter:
Can copper sulphate solution be stored in a zinc pot? Give a reason for your answer by referring to the values given below.
`E_(Zn^(2+)//Zn)^0 = -0.76 V E_(Cu^(2+)//Cu)^0 = + 0.34 V`
Chapter:
When a current of 0.75 ampere is passed through a CuSO4 solution for 25 minutes, 0.370 g of copper is deposited. Calculate the atomic weight of copper by using the given information.
Chapter:
Two metals A and B have standard reduction potential values, −0.76 V and +0.34 V, respectively.
Which of these metals will liberate H2 gas from dil. H2SO4? Why?
Chapter:
Why does the conductivity of a solution decrease on dilution of the solution?
Chapter:
Identify the compounds [A], [B] and [C] in the following reaction:
\[\ce{C2H5Br ->[KCN] [A] ->[LiAlH4][{[4H]}] [B] ->[HNO2][0^\circ-5^\circ C] [C]}\]
Chapter:
Identify the compounds [A], [B] and [C] in the following reaction:
\[\ce{CH3CH2COOH ->[NH3][\Delta] [A] ->[Δ] [B] ->[Br2/KOH] [C]}\]
Chapter:
Calculate the mass of ascorbic acid (molecular mass = 176 g mol−1) to be dissolved in 75 g of acetic acid to lower its freezing point by 1.5°C. Assume that the solute neither associates nor dissociates in solution.
(Kf for acetic acid = 3.9 K kg mol−1)
Chapter:
A solution of an organic compound was prepared by dissolving 6.8 g in 0.1 litre of water. Calculate the osmotic pressure of this solution at 25°C.
(Molecular mass of organic compound = 321.45 g mol−1)
Chapter:
Why are aquatic species more comfortable in cold water in comparison to warm water?
Chapter:
What happens when (write chemical equation) calcium acetate is subjected to dry distillation?
Chapter:
What happens when (write chemical equation) acetaldehyde is reduced with hydrogen in the presence of Zn/Hg and conc. HCl?
Chapter:
What happens when (write chemical equation) acetaldehyde is reduced with hydrogen in the presence of Zn/Hg and conc. HCl?
Chapter:
What happens when (write chemical equation) acetic acid is heated with ethyl alcohol in the presence of conc. H2SO4?
Chapter:
An organic compound [X] with molecular formula C2H4O forms compound [Y] on oxidation. Compound [X] undergoes haloform reaction. On treatment with HCN, compound [X] forms a product [Z] which on hydrolysis gives 2-hydroxy propanoic acid.
- Write down the structures of compounds [X] and [Y].
- Name the product formed when [X] reacts with dil. NaOH.
Chapter:
With reference to Valence Bond Theory (VBT), answer the following questions regarding the complex ion [Cr(NH3)6]3+.
- What is the oxidation number of chromium in the complex?
- State the magnetic behaviour of the complex.
- How many unpaired electrons are there in the complex?
- State the type of hybridisation of the central metal atom.
Chapter:
The coordination complex CoNO2Cl.5NH3 exist in two isomeric forms ‘P’ and ‘Q’. Isomer ‘P’ reacts with AgNO3 solution to give white precipitate whereas ‘Q’ does not give any precipitate with AgNO3 solution.
- Write the structural formula of isomers ‘P’ and ‘Q’.
- Name the type of isomerism involved.
Chapter:
Explain why an aqueous solution of potassium hexacyanidoferrate(II) does not give the test of ferrous ion.
Chapter:
- Write the electronic configuration of the following:
- d4 (high spin octahedral)
- d6 (low spin octahedral)
- Based on the above configuration, calculate the value of Crystal Field Splitting Energy (CFSE). (Ignore pairing energy)
Chapter:
Name the type of isomerism exhibited by the following pair of compounds:
[Co(NH3)5(ONO)]Cl2 and [Co(NH3)5(NO2)]Cl2
Chapter:
What type of isomerism is exhibited by the following pair of compounds?
[PtCl2(NH3)4]Br2 and [PtBr2(NH3)4]Cl2
Chapter:
Which of the following coordination complexes is an outer orbital complex? Explain.
Chapter:
Submit Question Paper
Help us maintain new question papers on Shaalaa.com, so we can continue to help studentsonly jpg, png and pdf files
CISCE previous year question papers ISC Class 12 Chemistry (Theory) with solutions 2025 - 2026
Previous year Question paper for CISCE ISC Class 12 -2026 is solved by experts. Solved question papers gives you the chance to check yourself after your mock test.
By referring the question paper Solutions for Chemistry (Theory), you can scale your preparation level and work on your weak areas. It will also help the candidates in developing the time-management skills. Practice makes perfect, and there is no better way to practice than to attempt previous year question paper solutions of CISCE ISC Class 12.
How CISCE ISC Class 12 Question Paper solutions Help Students ?
• Question paper solutions for Chemistry (Theory) will helps students to prepare for exam.
• Question paper with answer will boost students confidence in exam time and also give you an idea About the important questions and topics to be prepared for the board exam.
• For finding solution of question papers no need to refer so multiple sources like textbook or guides.
