CBSE EXAMINATION PAPER-2025

The following questions are case based questions. Read the passage carefully and answer the questions that follow.

The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. Rate of the reaction depends upon the nature of reactants, concentration of reactants, temperature, presence of catalyst, surface area of the reactants and presence of light. Rate of reaction is directly related to the concentration of reactant. Rate law states that the rate of reaction depends upon the concentration terms on which the rate of reaction actually depends, as observed experimentally. The sum of powers of the concentration of the reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously in order to bring about a chemical reaction is called molecularity of the reaction.

The following questions are case based questions. Read the passage carefully and answer the questions that follow.

The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. Rate of the reaction depends upon the nature of reactants, concentration of reactants, temperature, presence of catalyst, surface area of the reactants and presence of light. Rate of reaction is directly related to the concentration of reactant. Rate law states that the rate of reaction depends upon the concentration terms on which the rate of reaction actually depends, as observed experimentally. The sum of powers of the concentration of the reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously in order to bring about a chemical reaction is called molecularity of the reaction.

The following questions are case based questions. Read the passage carefully and answer the questions that follow.

The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. Rate of the reaction depends upon the nature of reactants, concentration of reactants, temperature, presence of catalyst, surface area of the reactants and presence of light. Rate of reaction is directly related to the concentration of reactant. Rate law states that the rate of reaction depends upon the concentration terms on which the rate of reaction actually depends, as observed experimentally. The sum of powers of the concentration of the reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously in order to bring about a chemical reaction is called molecularity of the reaction.

The following questions are case based questions. Read the passage carefully and answer the questions that follow.

The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. Rate of the reaction depends upon the nature of reactants, concentration of reactants, temperature, presence of catalyst, surface area of the reactants and presence of light. Rate of reaction is directly related to the concentration of reactant. Rate law states that the rate of reaction depends upon the concentration terms on which the rate of reaction actually depends, as observed experimentally. The sum of powers of the concentration of the reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously in order to bring about a chemical reaction is called molecularity of the reaction.

The following questions are case based questions. Read the passage carefully and answer the questions that follow.

The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. Rate of the reaction depends upon the nature of reactants, concentration of reactants, temperature, presence of catalyst, surface area of the reactants and presence of light. Rate of reaction is directly related to the concentration of reactant. Rate law states that the rate of reaction depends upon the concentration terms on which the rate of reaction actually depends, as observed experimentally. The sum of powers of the concentration of the reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously in order to bring about a chemical reaction is called molecularity of the reaction.

The following questions are case based questions. Read the passage carefully and answer the questions that follow.

The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. Rate of the reaction depends upon the nature of reactants, concentration of reactants, temperature, presence of catalyst, surface area of the reactants and presence of light. Rate of reaction is directly related to the concentration of reactant. Rate law states that the rate of reaction depends upon the concentration terms on which the rate of reaction actually depends, as observed experimentally. The sum of powers of the concentration of the reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously in order to bring about a chemical reaction is called molecularity of the reaction.

Answer the following questions :

Phenols undergo electrophilic substitution reactions readily due to the strong activating effect of OH group attached to the benzene ring. Since, the OH group increases the electron density more to 0— and — positions therefore OH group is ortho, para-directing. Reimer-Tiemann reaction is one of the examples of aldehyde group being introduced on the aromatic ring of phenol, ortho to the hydroxyl group. This is a general method used for the ortho-formylation of phenols.

Answer the following questions :

In case of association, abnormal molar mass of solute will

The magnetic moment is associated with its spin angular momentum and orbital angular momentum . Spin only magnetic moment value of Cr³⁺ ion (Atomic no. : Cr=24) is_____ .

Acidified KMnO₄ oxidises sulphite to

The correct IUPAC name of [Pt(NH₃)₂Cl₂]²⁺ is

Arrange the following compounds in increasing order of their boiling points:

  Alkyl halides undergoing nucleophilic bimolecular substitution reaction involve

Which is the correct order of acid strength from the following?

The acid formed when propyl magnesium bromide is treated with CO₂ followed by acid hydrolysis is

The best reagent for converting propanamide into propanamine is ________________.

Which of the following statements is not true about glucose?

An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because____________.

Assertion (A): [Cr(H₂O)₆]Cl₂ and [Fe(H₂O)₆]Cl₂ are examples of homoleptic complexes.

Reason (R) : All the ligands attached to the metal are the same.

Complete and balance the following chemical equations:

(a)2MnO₄⁻(aq) + 10I⁻(aq) + 16H⁺(aq) →

(b) Cr₂O²⁻₇(aq) +6Fe²⁺(aq) +14H⁺(aq)→

Write the reactions involved when D-glucose is treated with following reagents:

(a) HCN

(b) Br₂ water

Give reasons :

(a) Cooking is faster in pressure cooker than in an open pan.

(b) on mixing liquid X and Y , volume of the resulting solution decreases . what type of deviation from raoult's law is shown by the resulting solution ? what change in temperature would you observe after mixing liquids X and Y?

Would you expect benzaldehyde to be more reactive or less reactive in nucleophilic addition reactions than propanal ? Justify your answer.

A solution of glucose (molar mass =180 g mol⁻¹) in water has a boiling point of 100.20 ºC. Calculate the freezing point of the same solution. Molal constants for water Kf and Kb are 1.86 K kg mol⁻¹and 0.512 K kg mol⁻¹ respectively.

A certain reaction is 50% complete in 20 minutes at 300 K and the same reaction is 50% complete in 5 minutes at 350 K. Calculate the activation energy if it is a first order reaction. 

[R=8.314 J K⁻¹ mol⁻¹; log 4 =0.602]

The elements of 3d transition series are given as :    

Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn

Answer the following :

(a) Copper has exceptionally positive E°ₘ₂₊/ₘ value, why ?

(b) Which element is a strong reducing agent in +2 oxidation state and why ?

(c) Zn²⁺ salts are colourless. Why ?

How do you convert :                                                                  

(a) Chlorobenzene to biphenyl

(b) Propene to I-lodopropane

(c) 2-bromobutane to but-2-ene.

(a) Arrange the following compounds in increasing order of their boiling point : 

(CH₃)₂NH, CH₃CH₂NH₂, CH₃CH₂0H.

(b) Give plausible explanation for each of the following :

(i) Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.

(iI) Amides are less basic than amines.

(a) What is the difference between native protein and denatured protein ?

(b) Which one of the following is a disaccharide ? Glucose, Lactose, Amylose, Fructose

(c) Which vitamin is responsible for the coagulation of blood ?

(a) Write the cell reaction and calculate the e.m.f. of the following cell at 298 K:

Sn(s)|Sn²⁺(0.004 M)||H⁺(0.02 M)|H₂(g)(1 Bar)|Pt(s)

(Given: E°(ₛₙ₂₊/ₛₙ=-0.14 V, E°H₊|H₂₍ᵍ₎ₚₜ= 0.00 V)

(b) Account for the following observations:

(i) On the basis of E° values, O₂ gas should be liberated at anode but it is Cl₂ gas which is liberated in the electrolysis of aqueous NaCl;

(ii) Conductivity of CH₃COOH decreases on dilution.

(a) Write the anode and cathode reactions and the overall cell reaction occurring in a lead storage battery during its use.

(b) Calculate the potential for half-cell containing 0.01 M K₂Cr₂07(aq), 0.01 M Cr³⁺ (aq) and 1.0 x 10⁻⁴ M H⁺ (aq).

The half cell reaction is

Cr₂0²⁻₇(aq)+14H⁺(aq) + 6e⁻→2Cr³⁺(aq) + 7H₂0(l)

and the standard electrode potential is given as E⁰= 1.33 V.

[Given : log 10 = 1].

Answer the following :      

(a) Low spin tetrahedral complexes are not known.

(b) c0²⁺ is easily oxidised to C0³⁺ in the presence of a strong ligand [At. No. of co = 27]

(c) What type of isomerism is shown by the complex [Co(NH₃)₆] [Cr(CN)₆]?

(d) Why a solution[Ni(H₂O)₆]²⁺ is green while a solution of [Ni(CN)₄]²⁻is colourless.

(At. No. of Ni = 28)

(e) Write the IUPAC name of the following complex : [Co(NH₃)₅(C0₃)]Cl

(a) What is meant by 'Chelate effect' ? Give an example.

(b) Write the hybridization and magnetic behaviour of[Fe(CN)₆]⁴⁻ (Atomic number : Fe= 26)

(c)  If PtCl₂ • 2NH₃ does not react with AgN0₃, what will be its formula ?

(a)Carry out the following conversions:

(i) Ethanal to But-2-enal;

(ii) Propanoic acid to ethane.

(b) An alkene A with molecular formula C5H10 on ozonolysis gives a mixture of two compounds B and C. Compound B gives positive Fehling test and also reacts with iodine and NaOH solution. Compound C does not give Fehling solution test but forms iodoform. Identify the compounds A, B and C.