Dr. Vikas Yadav
November 3, 2021 at 3:24:54 AM
Directions: In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as:
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) Both assertion and reason are false.
1. Assertion: Valency of noble gas is 0.
Reason: Noble gases possess complete octet.
2. Assertion: F2 has lower bond dissociation enthalpy than Cl2.
Reason: Fluorine is more electronegative than chlorine.
3. Assertion: Acidic character of group 16 hydrides increases from H2O to H2Te.
Reason: Thermal stability of hydrides decreases down the group.
4. Assertion: Inter-halogen compounds are more reactive than halogens (except fluorine).
Reason: They all undergo hydrolysis giving halide ion derived from the smaller halogen and anion derived from larger halogen.
5. Assertion: Halogens are not found in free state in nature.
Reason: Halogens are highly reactive compounds.
6. Assertion: F2 has low reactivity.
Reason: F-F bond has high bond dissociation energy.
7. Assertion: Ozone layer in the upper region of atmosphere protects earth from UV radiations of sun.
Reason: Ozone is a powerful oxidising agent as compared to oxygen.
8. Assertion: S shows paramagnetic nature, when present in vapour state.
Reason: S exists as S2 in vapour state.
9. Assertion: F2 is a strong oxidising agent.
Reason: Electron gain enthalpy of fluorine is less negative.
10. Assertion: Pbl4 is not a stable compound.
Reason: Iodide stabilizes lower oxidation state.
11. Assertion: Solubility of noble gases in water decreases with increasing size of the noble gas.
Reason: Solubility of noble gases in water is due to dipole-induced dipole interaction.
Answers –
1. (a)
Noble gases possess the electronic configuration ns2 np6 and has 8 electrons in their outer shell, hence there valency is 0. Thus, both assertion and reason are true and reason is the correct explanation of assertion.
2. (b)
Fluorine is more electronegative than chlorine and the bond dissociation energy of fluorine atom is very small as compared to a chlorine atom. This is because the size of F2 is much smaller than Cl2 as a result inter-electonic repulsion works and it requires less energy to break up the fluorine molecule, making its bond dissociation energy lesser than that of chlorine molecule. Thus, both assertion and reason are true, but reason is not the correct explanation of assertion.
3. (b)
The acidic character of group 16 hydrides increases down the group from H2O to H2Te and thermal stability of hydrides decreases down the group due to decrease in bond (H—E) dissociation enthalpy down the group. Thus, both assertion and reason are true, but reason is not the correct explanation of assertion.
4. (b)
Inter-halogen compounds are more reactive than halogens because X—X′ bond in inter-halogens is weaker than X—X bond in halogen (except F—F bond). They all undergo hydrolysis giving halide ion derived from the smaller halogen and anion derived from larger halogen. Thus, both assertion and reason are true but reason is not the correct explanation of assertion.
5. (a)
Halogens are highly reactive as they have seven electrons in their outermost orbit and therefore, they will acquire an electron to attain noble gas configuration. Therefore, they do not occur in free state. Thus, both assertion and reason are true and reason is the correct explanation of assertion.
6. (d)
F2 is more reactive than other Halogens because its valence electrons are much closer to nucleus and it is more electronegative so, bonded electrons repel each other causing low bond dissociation enthalpy. Thus, both assertion and reason are false.
7. (b)
Ozone layer in the upper region of atmosphere filters the radiation coming from sun, hence serves as the protective layer. Ozone is a powerful oxidising agent as compared to oxygen as it is unstable. Thus, both assertion and reason are true but reason is not the correct explanation of assertion.
8. (a)
In vapour state, S exists as S2 and it behaves like O2. It has 2 unpaired electrons in antibonding pi orbitals. Presence of these unpaired electrons make S paramagnetic in nature. Thus, both assertion and reason are true and reason is the correct explanation of assertion.
9. (b)
The small size and higher electronegativity of fluorine makes it a stronger oxidising agent which means it readily accepts electrons. Electron gain enthalpy of fluorine is less negative. Electron gain enthalpy of fluorine is less negative because it is placed above chlorine in the periodic table. Thus, both assertion and reason are true but reason is not the correct explanation of assertion
10. (c)
PbI4 is not a stable compound because Pb shows (II) oxidation state more frequently than Pb (IV) due to inert pair effect. Iodide cannot stabilize higher oxidation states. Thus, assertion is true but reason is false.
11. (d)
Solubility of noble gases in water is due to dipole-induced dipole interaction. As the size of noble gas elements increases, they easily get polarised by the water molecules due to which the electron cloud gets distorted. Hence, solubility increases as the size of the atom of noble gas elements increases. Thus, both assertion and reason are false.