Question

Match the List-I with List-II.

	List-I (Compound)		List-II (Property)
(P)	$NO_2$	(1)	Paramagnetic
(Q)	NO	(2)	Dimerises on cooling
(R)	$Cl_2O$	(3)	Disproportionate either in hot or cold water
(S)	$ClO_2$	(4)	Act as both oxidizing agent and reducing agent
		(5)	Oxidation number on central atom = + 4

• A. P-(1), Q-(2), R-(3), S-(4)
• B. P-(2), Q-(1), R-(4), S-(3)
• C. P-(3), Q-(4), R-(1), S-(2)
• D. P-(4), Q-(3), R-(2), S-(1)

Answer 1

Answer: (B)

P-(2), Q-(1), R-(4), S-(3)

Answer 2

Let's analyze each compound in List-I and match its properties from List-II.

Analysis of (P) $NO_2$ (Nitrogen dioxide):

• Due to the unpaired electron, $NO_2$ readily dimerizes to form $N_2O_4$ (dinitrogen tetroxide) by pairing up the odd electrons. This process is exothermic and favored at lower temperatures (cooling).

Most characteristic match for (P) $NO_2$: Dimerization on cooling is a very prominent and characteristic property of $NO_2$. So, P $\rightarrow$ (2).

Analysis of (Q) NO (Nitric oxide):

• Nitric oxide (NO) is a stable molecule with an odd number of valence electrons, making it paramagnetic.

Most characteristic match for (Q) NO: Paramagnetism is a very characteristic property of NO, being a stable odd-electron molecule. So, Q $\rightarrow$ (1).

Analysis of (R) $Cl_2O$ (Dichlorine monoxide):

• Chlorine in $Cl_2O$ is in the +1 oxidation state, which is an intermediate state. Therefore, it can be oxidized to higher oxidation states or reduced to lower oxidation states. Hence, it can act as both an oxidizing agent and a reducing agent.

Most characteristic match for (R) $Cl_2O$: $Cl_2O$ (Cl in +1) can act as both oxidizing and reducing agent. So, R $\rightarrow$ (4).

Analysis of (S) $ClO_2$ (Chlorine dioxide):

• $ClO_2$ disproportionates directly in water: $2ClO_2 + H_2O \rightarrow HClO_2 + HClO_3$. Here, Cl goes from +4 to +3 and +5.

Most characteristic match for (S) $ClO_2$: $ClO_2$ directly disproportionates in water, which is a specific chemical property, making S $\rightarrow$ (3) a strong match.

Therefore, the most suitable unique matches are: P - (2) Q - (1) R - (4) S - (3)