a) Account for the following:i) NH3 acts as a Lewis base.ii) PCI3 fu

1.	a) Account for the following:i) NH3 acts as a Lewis base.ii) PCI3 fumes in moist air.iii) Fluorine shows only – 1 oxidation state.b) i) Suggest any two fluorides of Xenon.ii) Write a method to prepare any one of the above mentioned Xenon fluorides.ORa) Account for the following:i) H2O is a liquid while H2S is a gas.ii) Noble gases have very low boiling points.iii) NO2 dimerises to N2O4.b) i) What are interhalogen compounds?ii) Suggest any two examples of interhalogen compounds.
Answer» a) i) Nitrogen atom in NH₃ has one lone pair of electrons which is available for donation. There fore, it acts as a Lewis base. ii) PCI₃ hydrolyses in the presence of moisture giving fumes of HCI. PCI₃ + 3H₂O → H₃PO₃ + 3HCI iii) Fluorine is the most electronegative element and cannot exhibit any positive oxidation state. Fluorine atom hasno d orbitals in its valence shell and therefore cannot expand its octet. b) i) Xenon ditluoride, XeF₂ Xenon tetrafluoride, XeF₄ Xenon hexafluonde, XeF₆(any two) ii) XeF₂ is prepared by treating Xe with excess fluorine at 673 Kandl bar.Xe(g)+F2( g)⟶673 K,1 bar >XeF2( s) Or, XeF₄ is prepared by treating Xe with excess fluorine in 1: 5 ratio at 873 K and 7 bar. Xe(g)+2 F2( g)⟶B73 K,7bar→XeF4( s) Or, XeF₆ is prepared by treating Xe with excess fluorine in 1 :20 ratio at 573 K and 60 – 70 bar. Xe(g)+3 F2( g)⟶573 K,60−70bar⟶XeF6( s) OR a) i) Due to small size and high electronegativity of oxygen it is capable of forming hydrogen bond. Thus, water molecules can associate through intermolecular hydrogen bonds and hence ¡t exists as a liquid. Due to big large and low electronegativity of sulphur t is not capable of forming hydrogen bond. So hydrogen sulphide molecules cannot associate through intermolecular bonds and hence it exists as a gas. ii) Noble gases being monoatomic have no interatomic forces except weak dispersion forces and therefore, they are liquefied at very low temperatures. Hence, they have low boiling points. iii) NO₂ contains odd numberof valence elecrons. It behaves as a typical odd electron molecule. On dimensation, it is converted to stable N₂O₄molecule with even number of electrons. b) i) These are compounds formed by the reaction between two different halogens. ii) dF, BrF, IF, BrCI, ICI, dF₃, BrF₃, IF₃, ICI₃, IF₅, BrF₅, dF₅, IF₇

a) Account for the following:i) NH3 acts as a Lewis base.ii) PCI3 fumes in moist air.iii) Fluorine shows only – 1 oxidation state.b) i) Suggest any two fluorides of Xenon.ii) Write a method to prepare any one of the above mentioned Xenon fluorides.ORa) Account for the following:i) H2O is a liquid while H2S is a gas.ii) Noble gases have very low boiling points.iii) NO2 dimerises to N2O4.b) i) What are interhalogen compounds?ii) Suggest any two examples of interhalogen compounds.

Answer»

a) i) Nitrogen atom in NH₃ has one lone pair of electrons which is available for donation. There fore, it acts as a Lewis base.

ii) PCI₃ hydrolyses in the presence of moisture giving fumes of HCI. PCI₃ + 3H₂O → H₃PO₃ + 3HCI

iii) Fluorine is the most electronegative element and cannot exhibit any positive oxidation state. Fluorine atom hasno d orbitals in its valence shell and therefore cannot expand its octet.

b) i) Xenon ditluoride, XeF₂

Xenon tetrafluoride, XeF₄

Xenon hexafluonde, XeF₆(any two)

ii) XeF₂ is prepared by treating Xe with excess fluorine at 673 Kandl bar.Xe(g)+F2( g)⟶673 K,1 bar >XeF2( s)

Or,

XeF₄ is prepared by treating Xe with excess fluorine in 1: 5 ratio at 873 K and 7 bar.

Xe(g)+2 F2( g)⟶B73 K,7bar→XeF4( s)

Or,

XeF₆ is prepared by treating Xe with excess fluorine in 1 :20 ratio at 573 K and 60 – 70 bar.

Xe(g)+3 F2( g)⟶573 K,60−70bar⟶XeF6( s)

a) i) Due to small size and high electronegativity of oxygen it is capable of forming hydrogen bond. Thus, water molecules can associate through intermolecular hydrogen bonds and hence ¡t exists as a liquid.

Due to big large and low electronegativity of sulphur t is not capable of forming hydrogen bond. So hydrogen sulphide molecules cannot associate through intermolecular bonds and hence it exists as a gas.

ii) Noble gases being monoatomic have no interatomic forces except weak dispersion forces and therefore, they are liquefied at very low temperatures. Hence, they have low boiling points.

iii) NO₂ contains odd numberof valence elecrons. It behaves as a typical odd electron molecule. On dimensation, it is converted to stable N₂O₄molecule with even number of electrons.

b) i) These are compounds formed by the reaction between two different halogens.

ii) dF, BrF, IF, BrCI, ICI, dF₃, BrF₃, IF₃, ICI₃, IF₅,
BrF₅, dF₅, IF₇

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