ISC Board Class 12 Chemistry Sample Paper 2024-25: Download FREE Sample Paper PDF With Answer Key!

Question 1

(A)

Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:

[four, three, remains same, propane, ns1-2, increases, six, propane-2-ol, (n-1)d1-10, two, decreases, Clemmensen’s, Wolff-Kishner]

[4×1]

(i)

The molar conductance of a solution on dilution but the specific conductance of a solution on dilution.

(Understanding)

(ii)

In the complex ion [CoCl(en)2ONO]+, the coordination number and the oxidation number of the central metal ion are and (Understanding)

(iii)

Propanone on reaction with zinc amalgam in the presence of concentrated HCl gives and the reaction is called reduction. (Recall)

(iv)

The variation and magnitude of oxidation state in coordination complexes is due to the participation of inner electrons in addition to outer electrons. (Understanding)

(B)

Select and write the correct alternative from the choices given below.

[7×1]

(i)

The correct order of the increasing basic nature of Ammonia, Methylamine and Aniline is: (Analysis)

(a)

Methylamine < Aniline < Ammonia

(b)

Aniline < Methylamine < Ammonia

(c)

Ammonia < Aniline < Methylamine

(d)

Aniline < Ammonia < Methylamine

(ii)

Colligative properties of a solution are: (Understanding)

(P)

Independent of the nature of the solute

(Q)

Proportional to molecular mass of solute

(R)

Proportional to the concentration of solute

(S)

Independent of the amount of solvent

(a)

Only P and Q are correct

(b)

Only P and R are correct

(c)

Only P and S are correct

(d)

Only Q and S are correct

(iii)

According to Markownikoff’s rule, “The negative part of the halogen acid attaches itself with that C atom of an unsymmetrical alkene which has the least number of H-atom.”

Anti-Markownikoff’s addition of HBr is NOT observed in: (Analysis)

(a)

Propene

(b)

But-2-ene

(c)

But-1-ene

(d)

Pent-2-ene

(iv)

Most of the naturally occurring α-amino acids are optically active and have L-configuration. Which of the following amino acids is NOT asymmetric?

(Recall)

(a)

Valine

(b)

Alanine

(c)

Glycine

(d)

Leucine

(v)

Which one of the following complex ions has geometrical isomers?

(Understanding)

(a)

[Ni(NH3)5Br]+

(b)

[Cr(NH3)4en]3+

(c)

[Co(NH3)2(en)2]3+

(d)

[Co(NH3)6]3+

(vi)

Given below are two statements marked Assertion and Reason. Read the two statements carefully and select the correct option.

Assertion: Tertiary butyl bromide undergoes Wurtz reaction to give 2,2,3,3 tetramethyl butane.

Reason: In the Wurtz reaction, when the same alkyl halides react with sodium in dry ether to give hydrocarbon; the hydrocarbon formed contains double the number of carbon atoms present in the alkyl halide.

(Analysis)

(a)

Both Assertion and Reason are true and Reason is the correct explanation of assertion.

(b)

Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.

(c)

Assertion is true but Reason is false.

(d)

Both Assertion and Reason are false.

(vii)

Given below are two statements marked Assertion and Reason. Read the two statements carefully and select the correct option.

Assertion: There is a continuous increase in size among Lanthanoids with an increase in atomic number.

Reason: Lanthanoids do not show Lanthanoid contraction. (Analysis)

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

(b)

Both Assertion and Reason are true but Reason is not the correct explanation for assertion.

(c)

Assertion is true but Reason is false.

(d)

Both Assertion and Reason are false.

(C)

Read the passage carefully and answer the questions that follow.

[3×1]

A plant or any other living being maintains a reasonable balance of C-14 (radioactive carbon) in its tissue during its lifetime. C-14 is used to determine the age of fossils. In the upper atmosphere, neutrons present in the cosmic rays are captured to produce the following nuclear reaction.

7N14 + 0n1 6C14 + 1H1

The c-14 isotope is circulated in the atmosphere and gets absorbed by living organisms during photosynthesis. The ratio of C-14 to C-12 in living beings is 1:1012. Once the living being dies, the level of C-14 in the dead being decreases due to the following reaction.

6C14 7N14 + -1e0 + γ rays

The death of the plant brings an end to its tendency to take up C-14. The half-

the life period of C-14 is 5770 years. By knowing the concentration of C-14 in

the living plant and the piece of dead material at a particular time, the age of the material (fossil) can be determined.

(i)

Write the relation between the decay constant and the half-life period.

(Recall)

(ii)

In a piece of dead wood, the activity or concentration of C-14 is found to be one-third of its initial activity. Calculate the age of the old wood.

(Application)

(iii)

The half-life period (t1/2) for a first-order reaction is 30 minutes. Calculate the time taken to complete 87·5% of the reaction.

(Application)