CBSE EXAMINATION PAPER-2025

The spontaneous flow of the solvent through a semipermeable membrane from a pure solvent to a solution or from a dilute solution to a concentrated solution is called osmosis. The phenomenon of osmosis can be demonstrated by taking two eggs of the same size. In an egg, the membrane below the shell and around the egg material is semipermeable. The outer hard shell can be removed by putting the egg in dilute hydrochloric acid. After removing the hard shell, one egg is placed in distilled water and the other in a saturated salt solution. After some time, the egg placed in distilled water swells-up while the egg placed in salt solution shrinks. The external pressure applied to stop the osmosis is termed as osmotic pressure (a colligative property). Reverse osmosis takes place when the applied external pressure becomes larger than the osmotic pressure.

The charge required for the reduction of 1 mol of Mn0⁻₄ to Mn0₂ is

Which among the following is false statement?

The number of molecules that react with each other in an elementary reaction is a measure of the:

The element having [Ar]3d¹⁰4s¹ electronic configuration is:

The complex ions [Co(NH₃)₅(NO₂)]²⁺ and [Co(NH₃)₅(ONO)]²⁺ are called:

Which is the correct IUPAC name for

What will be formed after oxidation reaction of secondary alcohol with chromic anhydride (CrO₃)?

The conversion of phenol to salicylic acid can be accomplished by:

Which of the following is/are examples of denaturation of protein?

Nucleotides are joined together by:

Scurvy is caused due to deficiency of:

Assertion (A) : In a first order reaction, if the concentration of the reactant is doubled, its half-life is also doubled.

Reason (R) : The half-life of a reaction does not depend upon the initial concentration of the reactant in a first order reaction.

Assertion (A) : In a first order reaction, if the concentration of the reactant is doubled, its half-life is also doubled

Reason (R) : The half-life of a reaction does not depend upon the initial concentration of the reactant in a first order reaction.

Assertion (A) : Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.

Reason (R) : Aryl halides do not undergo nucleophilic substitution reaction with the anion formed by phthalimide.

Assertion (A) : Vitamin D cannot be stored in our body.

Reason (R) : Vitamin D is fat soluble vitamin and is not excreted from the body in urine.

The rate constant for a zero order reaction A→ P is 0.0030 mol L⁻¹s⁻¹. How long will it take for the initial concentration of A to fall from 0.10 M to 0.075 M ?       

The decomposition of NH₃ on platinum surface is zero order reaction. what are the rates of production of N₂ and H₂ if k = 2.5 x 10⁻⁴ mol L⁻¹ s⁻¹ ?

Define the following terms :

(a) Pseudo first order reaction

(b) Half-life period of reaction(t½)

Examine the following observations :

(a) Transition elements generally form coloured compounds.

(b) Zinc is not regarded as a transition element.

Name the following coordination compounds according to IUPAC norms :

(a) [Co(NH₃)₄(H₂O)Cl]Cl₂

(b) [CrC1₂(en)₂ ] Cl

At 25 ⁰C the saturated vapour pressure of water is 24 mm Hg. Find the saturated vapour pressure of a 5% aqueous solution of urea at the same temperature. (Molar mass of urea = 60 g mol⁻¹)

The electrical resistance of a column of 0.05 M NaOH solution of area 0.8 cm² and length 40 cm is 5 x 10³ ohm. Calculate its resistivity, conductivity and molar conductivity.    

Using valence bond theory, explain the hybridization and magnetic character of the following :       

(a) [Co(NH₃)₆]³⁺

(b) [Ni(CO)₄]    

[At. no. : Co = 27, Ni = 28]

(a) Define the following :    

(i)   Enantiomers

(ii)  Racemic mixture

(b) Why is chlorobenzene resistant to nucleophilic substitution reaction ?

Define the following terms :        

(a) Glycosidic linkage

(b) Invert sugar

(c) Oligosaccharides

(a) Give the IUPAC name of CH₃−CH=CH−CHO.

(b) Give a simple chemical test to distinguish between propanal and propanone.

(c) How will you convert the following :

(i) Toluene to benzoic acid

(ii) Ethanol to propan—2—ol

(iii) Propanal to 2—hydroxy propanoic acid

An organic compound 'A', molecular formula C₂H₆0 oxidises with Cr0₃ to form a compound 'B'. Compound 'B' on warming with iodine and aqueous solution of NaOH gives a yellow precipitate of compound 'C'. When compound 'A' is heated with conc. H₂S0₄ at 413 K gives a compound 'D', which on reaction with excess HI gives compound 'E'. Identify compounds 'A', 'B', 'C', 'D' and 'E' and write chemical equations involved.

(a) Write chemical equations of the following reactions :         

(i) Phenol is treated with conc. HNO3

(ii) Propene is treated with B H followed by oxidation by H202/OH-.

(iii) Sodium t-butoxide is treated with CH3 Cl.

(b) Give a simple chemical test to distinguish between butan—1—ol and butan—2—ol.

(c) Arrange the following in increasing order of acid strength : phenol, ethanol, water.