Chemistry Board Sample Paper 2025-2026 Science (English Medium) Class 12 Question Paper Solution

Which of the following reactions will lead to the formation of ethyl methyl ketone?

Heating CH₃CH(CH₃)CH₂OH with acidified Na₂Cr₂O₇.

Passing CH₃C(OH)CH₃ over heated copper.

Ozonolysis of CH₃CH₂C(CH₃) = CHCH₃

Acetylene on reaction with HgSO₄/H₂SO₄.

Consider the reaction and identify B and C:

\[\ce{CH3CH2CH2CH2Cl ->[NaOH + Ethanol] A}\]

\[\ce{A ->[H2O, H^+] B}\] and \[\ce{A ->[(i) B2H6 (ii) H2O2, OH^-]C}\]

B = C = Butanol

B = Butanol, C = Butene

B = Butan-2-ol, C = Butanol

B = Butene, C = Butan-2-ol

The counter ion in the coordination compound [Co(NH₃)₅(NO₂)]Cl₂ is ______.

Ammine

Cobalt

Chloride

Nitro

The organic compounds A, B and C are amines having equivalent molecular weight. A and B on reaction with benzene sulphonyl chloride give a white precipitate; however, the white precipitate obtained from compound B remains insoluble in NaOH.

The variation in the boiling point of A, B and C can be seen as:

A > B > C

B > A > C

A = B > C

C > B > A

70 gm solute is dissolved in 700 gm solvent to prepare a solution having density 1.5 g/ml. The ratio of its molality and molarity will be ______.

0.77

1.4

0.73

1.3

Match the column I and column II:

Column I		Column II
A.		(i)	Additional reaction
B.		(ii)	Elimination reaction
C.	\[\begin{array}{cc} \ce{Br\phantom{........................}}\\ |\phantom{.........................}\\ \ce{H3C-CH2-CH2-CH-CH2->[^-OH][]H3C-CH2-CH2-CH = CH2}\\ |\phantom{..............}\\ \ce{H\phantom{..............}}\\ \end{array}\]	(iii)	SN2 reaction
D.	\[\ce{CH3CH = CH2 + H-I ->H3CH2CH2I + CH3CHICH3}\]	(iv)	SN1 reaction

A - (i), B - (ii), C - (iii), D - (iv)

A - (iv), B - (ii), C - (iii), D - (i)

A - (i), B - (iii), C - (ii), D - (iv)

A - (iv), B - (iii), C - (ii), D - (i)

In o-cresol, the –OH group is attached to the carbon that is ______.

sp³ hybrid

sp² hybrid

sp hybrid

dsp² hybrid

Which of the following is laevorotatory in nature?

alpha-D-glucose

beta-D-glucose

beta-D-fructose

sucrose

The name inner transition metals is often used to refer to ______.

lanthanoids

actinoids

both lanthanoids and actinoids

d-block elements

\[\ce{\Lambda^{\circ}_m CH3COOH}\] can be calculated if the values of the following are given:

1. \[\ce{\Lambda^{\circ}_m HCl, \Lambda^{\circ}_m KCl and \Lambda^{\circ}_m CH3COOK}\]
2. \[\ce{\Lambda^{\circ}_m NaCl, \Lambda^{\circ}_m KCl and \Lambda^{\circ}_m CH3COONa}\]
3. \[\ce{\Lambda^{\circ}_m H2SO4, \Lambda^{\circ}_m Na2SO4 and \Lambda^{\circ}_m CH3COONa}\]

Only 1

Either 1 or 2

Either 1 or 3

Either 2 or 3

Which of the following will give a yellow or orange ppt. with 2,4-DNP?

1. Propanal
2. Propanone
3. Propanoic acid

(i) and (ii)

(ii) and (iii)

(i) and (iii)

(i), (ii) and (iii)

Identify the secondary benzylic halide and primary alkyl halide from the following:

(i) and (iii)

(iv) and (ii)

(iii) and (iv)

(i) and (ii)

Assertion (A): Secondary aliphatic amines react with nitrous acid to form aliphatic diazonium salts which being unstable, liberate nitrogen gas quantitatively.

Reason: Nitrogen gas evolved on reaction with nitrous acid can be used for the estimation of proteins and amino acids.

Select the most appropriate answer from the options given below:

Both A and R are true, and R is the correct explanation of A.

Both A and R are true, and R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Assertion (A): Care should always be taken to ensure that solutions that flow in the bloodstream are of the same osmotic pressure as that of the blood.

Reason (R): Sodium ions and potassium ions are responsible for maintaining proper osmotic pressure balance inside and outside of the cells of an organism.

Select the most appropriate answer from the options given below:

Both A and R are true, and R is the correct explanation of A.

Both A and R are true, and R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Assertion (A): Starch forms a colloidal solution with water.

Reason (R): Starch contains 80-85% of amylopectin, which is insoluble in water.

Select the most appropriate answer from the options given below:

Both A and R are true, and R is the correct explanation of A.

Both A and R are true, and R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Assertion (A): Secondary cells are used in inverters.

Reason (R): A primary cell can be recharged by passing current through it in the opposite direction after it has been used.

Select the most appropriate answer from the options given below:

Both A and R are true, and R is the correct explanation of A.

Both A and R are true, and R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

When 50 mL of phenol and 50 mL of aniline are mixed, predict whether the volume of the solution is equal to, greater than or less than 100 mL. Give a reason to support your answer.

Ritesh suggested adding salt to the box containing ice. He said this would keep the cold drink bottles cold for a longer time. How will Ritesh justify his suggestion?

BaCl₂ on reaction with Na₂SO₄ in aqueous solution gives white precipitate. If the two solutions are separated by a semi-permeable membrane, will there be appearance of a white precipitate due to osmosis?

Why does water stop boiling when sugar is added to boiling water?

Consider the graph for the reaction:

\[\ce{H2 + I2 {⇌} 2HI}\]

1. Calculate enthalpy of reaction and activation energy for the backward reaction.
2. How will the catalyst affect the rate of this reaction? Explain.

Carry out the following conversion: 

Nitrobenzene to 4-bromobenzenamine.

Carry out the following conversion:

Chlorophenylmethane to 2-phenyl-ethanamine.

Write the formula of the following coordination complex:

Diaquasilver(I) dichloridoargentate(I)

Write the formula of the following coordination complex:

Dihydroxidobis(triphenylphosphine)nickel(II)

The mechanism of formation of alcohols from alkenes is given below. Rectify the errors in the mechanism and rewrite the corrected steps:

Step 1
Step 2
Step 3

What will be the vapour pressure of a 1 molal aqueous solution of MgCl₂, assuming dissociation of MgCl₂ to be 70 mole percent?

(Vapor pressure of pure water at 25°C is 23.8 mm Hg.)

Write the Nernst equation for the following:

\[\ce{Ni_{(s)} + Cu^2+_{ (aq)} -> Ni^2+_{ (aq)} + Cu_{(s)}}\]

Write the Nernst equation for the following:

\[\ce{Al_{(s)} + FeSO4_{(aq)} -> Al2(SO4)3_{(aq)} + Fe_{(s)}}\]

Write the Nernst equation for the following:

\[\ce{Mg_{(s)} + Mg^2+_{ (aq)}//Ag^+_{ (aq)}/Ag_{(s)}}\]

Explain the following:

Toluene on treatment with Cl₂ in sunlight gives benzyl chloride, whereas when treated with Cl₂ in dark gives o-chlorobenzene and p-chlorobenzene.

Explain the following:

Finkelstein reaction is carried out in the presence of dry acetone.

Explain the following:

Neopentyl chloride has a lower boiling point than isopentyl chloride.

Which of the following elements will exhibit similar magnetic behaviour and why?

Magnesium (Atomic No. 12), Chromium (Atomic No. 24), Iron (Atomic No. 26) and Molybdenum (Atomic No. 42).

Which of the following elements will form white salts and why?

Zinc (Atomic No. 30), Scandium (Atomic No. 21), Nickel (Atomic No. 28) and Vanadium (Atomic No. 23).

Arrange the products obtained in the following cases in the increasing order of their pK_a values:

1. Oxidation of ethanol in the presence of acidified potassium dichromate.
2. Reaction of propanoic acid with Br₂ in the presence of red phosphorus.
3. Reaction of isopropyl magnesium bromide with carbon dioxide, followed by hydrolysis.
4. Reaction of propanoic acid with Cl₂ in the presence of red phosphorus.

Carry out the following conversion. 

Butan-2-one to 3-Methylpentan-3-ol.

Carry out the following conversion.

Anisole to 4-Methoxytoluene.

How is phenol converted into the following?

Benzene

Carry out the following conversion:

Chloroethane to Ethoxyethane.

Are the enthalpies of atomisation of Zinc and Copper matched correctly? Justify your answer.

Out of sulphuric acid and hydrochloric acid, which acid will you prefer for permanganate titrations and why?

\[\ce{5NO^–_2 + 2MnO^–_4 + 6H+ ->}\]

Based on the information provided above, answer the following questions:

I. Is it possible to identify whether the given solution is 1 M NaOH or 1 M HCl using the conductivity meter? Justify your answer. (1)

II. What is the possible pH value of the solution if the glow of the green LED is medium and the red LED glows very brightly? (1)

(i) 1 (ii) 13 (iii) 5 (iv) 8

1. (i) and (ii)
2. (i) and (iii)
3. (ii) and (iv)
4. (iii) and (iv)

OR

Write down the observations if the conductivity meter is dipped in distilled water.

III. Refer to the table given below and draw the molar conductivity vs. concentration curve for solutions A and B. (2)

Based on the information provided above, answer the following questions:

1. Why is the Fe(III)-EDTA complex stable as compared to ferrous sulphate? (1)
   OR
   What happens when hard water is titrated against Na₂EDTA?
2. You are a doctor working in Somalia. Will you recommend iron-fortified food to your patients? Support your answer with references from the passage. (1)
3. 1. What is the denticity of the ligand in the Fe(III)-EDTA complex? Name the atom(s) through which it can bind to the central metal ion.  (1)
   2. Write the structure of EDTA. (1)

Write the structure of the expected product of the Cannizzaro reaction of 2-chlorobenzaldehyde.

How would the presence of an −SO₃H group affect the basic strength of aniline?

Convert acetic acid to ethanamine.

Write the steps to prepare Benzoic acid from Benzoyl chloride.

Propanal and Propanone

Write the structure of the expected product of the Wolf-Kishner reduction of 2-methylbutanal.

How would the presence of a −SO₃H group affect the acidic strength of benzoic acid?

Prepare acetic acid from ethanamine.

Convert aniline to benzoic acid.

Give a simple chemical test to distinguish between the following pair of compounds:

Ethanal and Propanal

Identify and give any one point of difference between the protein present in the hair and protein present in egg albumin.

Both glucose and sucrose have an aldehydic group, then why does only glucose reduces Fehling’s Reagent and not sucrose?

Give a reason for the following observations:

Amino acids behave like salts.

What chemical change takes place during curdling of milk?

Doctor advised a 50 year old woman to get enough exposure to sunlight and add fish and egg yolk to her diet. What possible disease did the doctor diagnose?

Identify and give any one point of difference between the carbohydrate present in cane sugar and the carbohydrate present in milk.

Glucose is an aldohexose and a monosaccharide. Which oxidising agent should be used to bring about oxidation of only the aldehydic group present in glucose?

Amino acid HOOC–CH₂CH(NH₂)CH₂COOH. Predict whether the pH of this amino acid will be > 7, 7 or < 7.

Name the two major molecular shapes formed due to the folding of the secondary structure of proteins.

Ashish’s gums bleed frequently. The doctor’s prescription mentioned that Ashish is suffering from scurvy. Help him to identify two food sources to help him recover faster.

The rate of a reaction triples when the temperature changes from 298 K to 318 K. Calculate the energy of activation of the reaction, assuming that it does not change with temperature.

(Given: R = 8.314 JK⁻¹ mol⁻¹, log 3 = 0.4771)

Identify the order of reaction and write its integrated rate equation, mentioning what each term in the equation represents.

Consider the following first-order thermal decomposition of SO₂Cl₂ at a constant volume.

\[\ce{SO2Cl2_{(g)}->SO2_{(g)} + Cl2_{(g)}}\]

If the total pressure of the gases is found to be 200 torr after 10 seconds and 300 torr upon the complete decomposition of SO₂Cl₂. Calculate the rate constant.

(Given log 3 = 0.4771, log 2 = 0.3010)

For a bimolecular elementary reaction, \[\ce{A + B -> Products}\]. Write the expression for the rate of reaction relating temperature and activation energy for the reaction and also mention what each term represents in the equation.