Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

Match the statement given in Column I with the phenomenon given in Column II.

Assertion: An ordinary filter paper impregnated with collodion solution stops the flow of colloidal particles.

Reason: Pore size of the filter paper becomes more than the size of colloidal particle.

Assertion: Colloidal solutions show colligative properties.

Reason: Colloidal particles are large in size.

Assertion: Colloidal solutions do not show brownian motion.

Reason: Brownian motion is responsible for stability of sols.

Assertion: Coagulation power of Al³⁺ is more than Na⁺.

Reason: Greater the valency of the flocculating ion added, greater is its power to cause precipitation (Hardy Schulze rule).

Which of the following are peroxoacids of sulphur?

An amorphous solid “A” burns in air to form a gas “B” which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous \[\ce{KMnO4}\] solution and reduces \[\ce{Fe^{3+}}\] to \[\ce{Fe^{2+}}\]. Identify the solid “A” and the gas “B” and write the reactions involved.

The reaction \[\ce{Ar\overset{+}{N2}Cl- ->[Cu/HCl] ArCl + N2 + CuCl}\] is anmed as ______.

Which of the following cannot be prepared by Sandmeyer’s reaction?

(i) Chlorobenzene

(ii) Bromobenzene

(iii) Iodobenzene

(iv) Fluorobenzene

Arrange the following compounds in increasing order of dipole moment.

\[\ce{CH3CH2CH3, CH3CH2NH2, CH3CH2OH}\]

Which of the following terms are correct about enzyme?

(i) Proteins

(ii) Dinucleotides

(iii) Nucleic acids

(iv) Biocatalysts

Activation energy for the acid catalysed hydrolysis of sucrose is 6.22 kJ mol^–1, while the activation energy is only 2.15 kJ mol^–1 when hydrolysis is catalysed by the enzyme sucrase. Explain.

Assertion: In presence of enzyme, substrate molecule can be attacked by the reagent effectively.

Reason: Active sites of enzymes hold the substrate molecule in a suitable position.

Give reasons to support the answer:

3-Hydroxy pentan-2-one shows positive Tollen’s test.

Define coagulation.

State the Hardy-Schulze rule.

What is electrophoresis?

Define the following term:

Coagulation

Why a negatively charged sol is obtained when AgNO₃ solution is added to KI solution?

Write the structures of A, B and C in the following reaction: