NCERT solutions for Chemistry [English] Class 12 chapter 7 - The p-block Elements [Latest edition]

Why are pentahalides more covalent than trihalides?

Why is BiH₃ the strongest reducing agent amongst all the hydrides of Group 15 elements?

Account for the following:

N₂ is less reactive at room temperature.

Mention the conditions required to maximise the yield of ammonia.

How does ammonia react with a solution of Cu²⁺?

What is the covalence of nitrogen in N₂O₅?

Bond angle in `PH_(4)^(+)` is higher than that in PH₃. Why?

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

What happens when PCl₅ is heated?

Write a balanced equation for the hydrolytic reaction of PCl₅ in heavy water.

What is the basicity of H₃PO₄?

What happens when 

H₃PO₃ is heated ?

Write the reactions involved.

List the important sources of sulphur.

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

Why is H₂O a liquid and H₂S a gas?

Which of the following does not react with oxygen directly?

Zn, Ti, Pt, Fe

Complete the following reactions: C₂H₄ + O₂ →

Complete the following reactions:  4Al + 3O₂ →

Why does O₃ act as a powerful oxidising agent?

How is O₃ estimated quantitatively?

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

Comment on the nature of two S−O bonds formed in SO₂ molecule. Are the two S−O bonds in this molecule equal?

How is the presence of SO₂ detected?

Mention three areas in which H₂SO₄ plays an important role.

Write the conditions to maximize the yield of H₂SO₄ by contact process.

Why is `K_(a_2) "<<" K_(a_1)` for `H_2SO_4` in water?

Considering the parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy, compare the oxidising power of F₂ and Cl₂.

Give two examples to show the anomalous behaviour of fluorine.

Sea is the greatest source of some halogens. Comment.

Give the reason for bleaching action of Cl₂.

Name two poisonous gases which can be prepared from chlorine gas.

Why is ICl more reactive than I₂?

Account for the following:

Helium is used in diving apparatus.

Balance the following equation: XeF₆ + H₂O → XeO₂F₂ + HF

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

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

Why does the reactivity of nitrogen differ from phosphorus?

Discuss the trends in chemical reactivity of group 15 elements.

Why does NH₃ form hydrogen bond but PH₃ does not?

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

How is ammonia manufactured industrially?

Give the resonating structures of NO₂ and N₂O₅.

The HNH angle value is higher than HPH, HAsH and HSbH angles. Why? [Hint: Can be explained on the basis of sp³ hybridisation in NH₃ and only s−p bonding between hydrogen and other elements of the group].

Why does R₃P=O exist but R₃N=O does not (R = alkyl group)?

Nitrogen exists as diatomic molecule and phosphorus as P₄. Why?

Write main differences between the properties of white phosphorus and red phosphorus.

Why does nitrogen show catenation properties less than phosphorus?

Give the disproportionation reaction of H₃PO₃

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

Justify the placement of O, S, Se, Te and Po in the same group of the periodic table in terms of electronic configuration, oxidation state and hydride formation.

Why is dioxygen a gas but sulphur a solid?

Knowing the electron gain enthalpy values for O → O⁻ and O → O²⁻ as −141 and 702 kJ mol⁻¹ respectively, how can you account for the formation of a large number of oxides having O²⁻ species and not O⁻? (Hint: Consider lattice energy factor in the formation of compounds).

Which aerosols deplete ozone?

Describe the manufacture of H₂SO₄ by contact process?

How is SO₂ an air pollutant?

Why are halogens strong oxidising agents?

Account for the following :

Fluorine forms only one oxoacid HOF

Explain why inspite of nearly the same electronegativity, oxygen forms hydrogen bonding while chlorine does not.

Write two uses of ClO₂.

Why are halogens coloured?

Write the reactions of F₂ and Cl₂ with water.

How can you prepare Cl₂ from HCl and HCl from Cl₂? Write reactions only.

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

What are the oxidation states of phosphorus in H₃PO₃

What are the oxidation states of phosphorus in the following:

 PCl₃ 

What are the oxidation states of phosphorus in the following:

Ca₃P₂

What are the oxidation states of phosphorus in the following:

Na₃PO₄

What are the oxidation states of phosphorus in the following:

POF₃

Write balanced equations for NaCl is heated with sulphuric acid in the presence of MnO₂

Write balanced equations for Chlorine gas is passed into a solution of NaI in water.

How are xenon fluorides XeF₂, XeF₄ and XeF₆ obtained?

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

How are XeO₃ and XeOF₄ prepared?

Arrange the following in the order of property indicated for each set:

 F₂, Cl₂, Br₂, I₂ - increasing bond dissociation enthalpy.

Arrange the following in the order of property indicated for each set:

HF, HCl, HBr, HI - increasing acid strength.

Which one of the following does not exist?

(i) XeOF₄ 

(ii) NeF₂

(iii) XeF₂ 

(iv) XeF₆

Give the formula and describe the structure of a noble gas species which is isostructural with

`ICI_4^(-)`

Give the formula and describe the structure of a noble gas species which is isostructural with:

`IBr_2^(-)`

Give the formula and describe the structure of a noble gas species which is isostructural with:

`BrO_3^(-)`

Why do noble gases have comparatively large atomic sizes?

Answer the following.

List the uses of Neon and argon gases.