CBSE EXAMINATION PAPER-2025

The a-amino acids are the building blocks of proteins. All a-amino acids exist as zwitter ion due to which they show amphoteric behaviour. All amino acids are joined through peptide bond. Proteins are broadly classified as globular proteins and fibrous proteins. Globular proteins are water soluble, whereas fibrous proteins are not. The complete structure of protein is discussed at four different levels i.e. primary, secondary, tertiary and quaternary structures. Protein loses its biological activity in denatured form.

According to Werner’s theory of coordination compounds:

Which of the following complex ion is not optically active?

Which of the following is the softest metal?

The freezing point of one molal KCl solution, assuming KCl to be completely dissociated in water, is: (Kf for water = 1·86 K kg mol⁻¹)

A solution of acetone in ethanol:

Which of the following cell converts the energy of combustion of fuel into electrical energy?

The unit of rate and rate constant are same for a:

Pyranose ring of glucose is formed due to the reaction between:

Assertion (A) : Actinoids show wide range of oxidation states.

Reason (R) : Actinoids are radioactive in nature .

Assertion (A) : Hydrolysis of an ester follows first order kinetics.

Reason (R) : The concentration of water does not get altered much during the reaction.

Assertion(A): Boiling point of (CH3)3N is higher than that of CH₃CH₂CH₂NH₂.

Reason (R) : Hydrogen bonding is more extensive in CH₃CH₂CH₂NH₂.

Assertion (A) : Phenol is strongly acidic as compared to ethanol.

Reason (R) : Phenoxide ion is more stable than ethoxide ion.

State Henry’s law. Why are aquatic species more comfortable in cold water as compared to warm water ?

Write IUPAC names of the following coordination compounds :

(i) [CoCl₂(en)₂]SO₄

(ii) K₃[Fe(C₂O₄)₃]

Differentiate between :

(i) Double salt and Complex compound

(ii) Didentate ligand and Ambidentate ligand

How do you explain the following ?

(a) Presence of an aldehydic group in glucose.

(b) Presence of five – OH groups in glucose.

Give reasons for the following :

(a) The pH of aqueous NaCl increases when it is electrolysed.

(b) Unlike dry cell, mercury cell has a constant cell potential through its lifetime.

(c) Conductivity of solution decreases with dilution.

Answer the following about the complexes [FeF₆]³⁻ and [Fe(CN)₆]⁴⁻ :

(i) Write the hybridization involved in each case.

(ii) Which of them is the outer orbital complex and which one is the inner orbital complex ?

(iii) Compare their magnetic behaviour.

[Atomic number : Fe = 26]

(i) What happens to the colour of complex [Ti(H₂O)₆]³⁺ when heated gradually ?

(ii) Write the electronic configuration for d⁵ ion if Δₒ < P.

(iii) Write the hybridization and magnetic behaviour of the complex [Ni(CO)₄].

[Atomic number : Ni = 28]

A compound (A) with molecular formula C₄H₅N on reduction with DIBAL-H followed by hydrolysis, gives a compound (B). Compound (B) gives positive Tollens’ test but does not give iodoform test. Compound (B) can also be obtained when ethanal is treated with dilute NaOH followed by heating. Identify (A) and (B). Write the reactions of (A) with DIBAL-H followed by hydrolysis.

How will you obtain the following from aniline ? Give chemical equations only.

(a) Sulphanilic acid

(b) Phenylisocyanide

(c) Acetanilide

Vapour pressure of pure water at 298 K is 24·8 mm Hg. Calculate the lowering in vapour pressure of an aqueous solution which freezes at– 0·3°C. (Kf of water = 1·86 K kg mol⁻¹)