Chemistry

The p-Block Elements.

Question:

Discuss the general characteristics of Group 15 elements with reference to their electronic configuration, oxidation state, atomic size, ionisation enthalpy and electronegativity.

Answer:

In group 15 of the Periodic Table, the elements, nitrogen (7N), phosphorus (15P), arsenic (33As), antimony (51Sb) and bismuth (83Bi) are present. The elements of this group can exhibit various oxidation states ranging between -3 to + 5. Negative oxidation state will be exhibited when they combine with less electronegative element andpositive oxidation state will be exhibited with more electronegative element. Positive oxidation state becomes more favourable as we more down the group due to increasing metallic character & electropositivity. Although due to inert pair effect the stability of +5 state will also decrease. The only stable compound of Bi (V) is BiF5.
The atomic (covalent) and ionic radii (in a particular oxidation state) of the elements of nitrogen family (group 15) are smaller than the corresponding elements of carbon family (group 14). On moving down the group, the covalent and ionic radii (in a particular oxidation state) increase with increase in atomic number. There is a considerable increase in covalent radius from N to P. However, from As to Bi, only a small increase is observed.
As the size increases on moving down the group, the ionisation enthalpy increases. The ionisation enthalpy of nitrogen group elements is more than the corresponding elements of oxygen group. This is because of more stable half filled outermost p- subshell of nitrogen group elements. Electronegativity decreases down the group with increase in atomic size.

previuos
next

The p-Block Elements.

Q 1.

Why are halogens strong oxidising agents?

Q 2.

How does ammonia react with a solution of Cu2+?

Q 3.

Give the reason for bleaching action of Cl2.

Q 4.

 Write balanced equations for the following:
(i) NaCl is heated witlrsulphuric acid in the presence of MnO2
(ii) Chlorine gas is passed into a solution of Nal in water.

Q 5.

Write the order of thermal stability of the – hydrides of Group 16 elements.

Q 6.

How is nitrogen prepared in the laboratory? Write the chemical equations of the reactions . involved.

Q 7.

Give the resonating structures of N02 and N2O5.

Q 8.

Match the formulas of oxides given in Column I with the type of oxide given in Column II and mark the correct option.
ncert-exemplar-problems-class-12-chemistry-p-block-elements-47

Q 9.

Describe the manufacture of H2SO4 by contact process?

Q 10.

What happens when sulp’hur dioxide is passed through an aqueous solution of Fe(III) salt?

Q 11.

 Why does nitrogen show catenation properties less than phosphorus ? (C.B.S.E. Foreign 2009)

Q 12.

What happens when white phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO2 ?

Q 13.

How is O3 estimated quantitatively?

Q 14.

Can PCl5 act as an oxidising as well as a reducing agent Justify.

Q 15.

Write two uses of ClO2

Q 16.

What inspired N. Bartlett for carrying out reaction between Xe and PtF6?

Q 17.

Which of the following acid forms three series of salts?
(a) H2PO2  (b) H3BO3 (C)H3PO4(d)H3PO3

Q 18.

Which of the following statements are correct?
(a) All three N – O bond lengths in HNO3 are equal.
(b) All P – Cl bond lengths in PCl5 molecule in gaseous state are equal.
(c) P4  molecule in white phosphorus have angular strain therefore white phosphorus is very reactive.
(d) PCl5 is ionic in solid state in which cation is tetrahedral and anion is octahedral.

Q 19.

Which of the following statements are true?
(a) Only type of interactions between particles of noble gases are due to weak dispersion forces.
(b) Ionisation enthalpy of.molecular oxygen is very close to that of xenon.
(c) Hydrolysis of XeF6 is a redox reaction.
(d) Xenon fluorides are not reactive.

Q 20.

 Why does R3P=0 exist but R3N=0 does not (R is an alkyl group) ?

Q 21.

Write a balanced equation for the hydrolytic reaction of PC is in heavy water.

Q 22.

How is the presence of SO2 detected ?

Q 23.

If chlorine gas is passed through hot NaOH solution, two changes are observed in the oxidation number of chlorine during the reaction. These are —— and ——-

Q 24.

Which of the following options are not in accordance with the properly mentioned against them?
ncert-exemplar-problems-class-12-chemistry-p-block-elements-20

Q 25.

In which of the following reactions cone. H2S04 is used as an oxidizing reagent?
ncert-exemplar-problems-class-12-chemistry-p-block-elements-25

Q 26.

 Why is N2 less reactive at room temperature?

Q 27.

Write the conditions to maximise the yield of H2SO4 by Contact process.

Q 28.

Give two examples to show the anomalous behaviour of fluorine.

Q 29.

 Write two uses of ClO2

Q 30.

Complete the following reactions:
(i)C2H2  + O2 -> (ii) 4Al + 3 O2 ->

Q 31.

What happens when sulp'hur dioxide is passed through an aqueous solution of Fe(III) salt?

Q 32.

Why does nitrogen show catenation properties less than phosphorus?

Q 33.

With what neutral molecule is CIO isoelectronic? Is that molecule a Lewis base?

Q 34.

How are XeO3  and XeOF4prepared?

Q 35.

Why do noble gases have comparatively large atomic sizes?

Q 36.

In qualitative analysis when H2S is passed through an aqueous solution of salt acidified with dil. HCl, a black precipitate is obtained. On boiling the precipitate with dil. HNO3, it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives
ncert-exemplar-problems-class-12-chemistry-p-block-elements-3

Q 37.

In PCl5, phosphorus is in sp3d hybridised state but all its five bonds are not equivalent. Justify your answer with reason.

Q 38.

 Why are pentahalides more covalent than trihalidcs?

Q 39.

 What happens when PCl5 is heated?

Q 40.

Why has it been difficult to study the chemistry of radon?

Q 41.

 How is nitrogen prepared in the laboratory? Write the chemical equations of the reactions . involved.

Q 42.

Why is dioxygen a gas but sulphur a solid?

Q 43.

 How is SO2 an air pollutant?

Q 44.

 With which neutral molecule is ClO isoelectronic? Is this molecule Lewis acid or base ? (Pb. Board 2009)

Q 45.

 How are XeOand XeOF4prepared?

Q 46.

 Why do noble gases have comparatively large atomic size?

Q 47.

 List the uses of neoirand argon gases.

Q 48.

Why is N2 less reactive at room temperature?

Q 49.

Mention the conditions required to maximise the yield of ammonia.

Q 50.

Bond angle in PH4+ is higher than that in PH3. Why?