Some Basic Principles and Techniques's Question 57 | Chemistry XI - Part 2 | NCERT Exemplar Questions

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MCQ (Single Correct Answer)

Assertion (A) Pent-1-ene and pent-2-ene are position isomers.

Reason (R) Position isomers differ in the position of functional group or a substituent.

Both A and R are correct and R is the correct explanation of A

Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$

Both A and R are not correct

A is not correct but R is correct

MCQ (Single Correct Answer)

Assertion (A) All the carbon atoms in $\mathrm{H}_2 \mathrm{C}=\mathrm{C}=\mathrm{CH}_2$ are $s p^2$ - hybridised.

Reason (R) In this molecule all the carbon atoms are attached to each other by double bonds.

Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$

Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$

Both $A$ and $R$ are not correct

A is not correct but R is correct

MCQ (Single Correct Answer)

Assertion (A) Sulphur present in an organic compound can be estimated quantitatively by Carius method.

Reason (R) Sulphur is separated easily from other atoms in the molecule and gets precipitated as light yellow solid.

Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$

Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$

Both A and R are not correct

A is not correct but R is correct

MCQ (Single Correct Answer)

Assertion (A) Components of a mixture of red and blue inks can be separated by distributing the components between stationary and mobile phases in paper chromatography.

Reason (R) The coloured components of inks migrate at different rates because paper selectively retains different components according to the difference in their partition between the two phases.

Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$

Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$

Both A and R are not correct

$A$ is not correct but $R$ is correct

Subjective

1 What is meant by hybridisation? Compound $\mathrm{CH}_2=\mathrm{C}=\mathrm{CH}_2$ contains $s p$ or $s p^2$-hybridised carbon atoms. Will it be a planar molecule?

Explanation

Hybridisation is mixing of atomic orbitals to form new hybrid orbitals. The new orbital have the same total electron capacity as the old ones. The properties and energies of the new hybridised orbitals are an average of the unhybridised orbitals.

Hybridisation can be found by counting number of $\sigma-$ bonds around the carbon atom.

$$\begin{aligned} 3 \sigma & =s p^2 \text {-hybridisation } \\ 2 \sigma & =s p \text {-hybridisation } \end{aligned}$$

In allene, carbon atoms 1 and 3 are $s p^2$-hybridised as each one of them is joined by a double bond. And, carbon atom 2 is $s p$-hybridised as it has two double bonds at each of its side. Therefore, the two $\pi$-bonds are perpendicular to each other, in allene, as shown below.

$\mathrm{H}_a$ and $\mathrm{H}_b$ lie in the plane of paper while $\mathrm{H}_c$ and $\mathrm{H}_d$ lie in a plane perpendicular to the plane of the paper. Hence, the allene molecule as a whole is non-planar.

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