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

## Chapter 7: The p-block Elements

Extra questions

### NCERT solutions for Class 12 Chemistry Chapter 7 The p-block Elements Extra questions

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

[Pages 169 - 205]

### NCERT solutions for Class 12 Chemistry Chapter 7 The p-block Elements [Pages 169 - 205]

Q 1 | Page 169

Why are pentahalides more covalent than trihalides?

Q 2 | Page 169

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

Q 3 | Page 170

Account for the following:

N2 is less reactive at room temperature.

Q 4 | Page 172

Mention the conditions required to maximise the yield of ammonia.

Q 5 | Page 172

How does ammonia react with a solution of Cu2+?

Q 6 | Page 173

What is the covalence of nitrogen in N2O5?

Q 7 | Page 177

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

Q 8 | Page 177

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

Q 9 | Page 177

What happens when PCl5 is heated?

Q 10 | Page 177

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

Q 11 | Page 180

What is the basicity of H3PO4 ?

Q 12 | Page 180

What happens when

H3PO3 is heated ?

Write the reactions involved.

Q 13 | Page 183

List the important sources of sulphur.

Q 14 | Page 183

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

Q 15 | Page 183

Why is H2O a liquid and H2S a gas?

Q 16 | Page 185

Which of the following does not react with oxygen directly?

Zn, Ti, Pt, Fe

Q 17.1 | Page 185

Complete the following reactions: C2H4 + O2 →

Q 17.2 | Page 185

Complete the following reactions:  4Al + 3O2 →

Q 18 | Page 187

Why does O3 act as a powerful oxidising agent?

Q 19 | Page 187

How is O3 estimated quantitatively?

Q 20 | Page 189

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

Q 21 | Page 189

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

Q 22 | Page 189

How is the presence of SO2 detected?

Q 23 | Page 191

Mention three areas in which H2SO4 plays an important role.

Q 24 | Page 191

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

Q 25 | Page 191

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

Q 27 | Page 196

Give two examples to show the anomalous behaviour of fluorine.

Q 28 | Page 196

Sea is the greatest source of some halogens. Comment.

Q 29 | Page 198

Give the reason for bleaching action of Cl2.

Q 30 | Page 198

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

Q 31 | Page 202

Why is ICl more reactive than I2?

Q 32 | Page 205

Account for the following:

Helium is used in diving apparatus.

Q 33 | Page 205

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

Q 34 | Page 205

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

[Pages 207 - 208]

### NCERT solutions for Class 12 Chemistry Chapter 7 The p-block Elements [Pages 207 - 208]

Q 1 | Page 207

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

Q 2 | Page 207

Why does the reactivity of nitrogen differ from phosphorus?

Q 3 | Page 207

Discuss the trends in chemical reactivity of group 15 elements.

Q 4 | Page 207

Why does NH3 form hydrogen bond but PH3 does not?

Q 5 | Page 207

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

Q 6 | Page 207

How is ammonia manufactured industrially?

Q 7 | Page 207

Illustrate how copper metal can give different products on reaction with HNO3.

Q 8 | Page 207

Give the resonating structures of NO2 and N2O5.

Q 9 | Page 207

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].

Q 10 | Page 207

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

Q 11 | Page 207

Explain why NH3 is basic while BiH3 is only feebly basic.

Q 12 | Page 207

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

Q 13 | Page 207

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

Q 14 | Page 207

Why does nitrogen show catenation properties less than phosphorus?

Q 15 | Page 207

Give the disproportionation reaction of H3PO3

Q 16 | Page 207

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

Q 17 | Page 207

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.

Q 18 | Page 207

Why is dioxygen a gas but sulphur a solid?

Q 19 | Page 207

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).

Q 20 | Page 207

Which aerosols deplete ozone?

Q 21 | Page 207

Describe the manufacture of H2SO4 by contact process?

Q 22 | Page 207

How is SO2 an air pollutant?

Q 23 | Page 207

Why are halogens strong oxidising agents?

Q 24 | Page 207

Account for the following :

Fluorine forms only one oxoacid HOF

Q 25 | Page 207

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

Q 26 | Page 207

Write two uses of ClO2.

Q 27 | Page 207

Why are halogens coloured?

Q 28 | Page 207

Write the reactions of F2 and Cl2 with water.

Q 29 | Page 207

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

Q 30 | Page 207

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

Q 31.1 | Page 207

What are the oxidation states of phosphorus in H3PO3

Q 31.2 | Page 207

What are the oxidation states of phosphorus in the following:

PCl

Q 31.3 | Page 207

What are the oxidation states of phosphorus in the following:

Ca3P2

Q 31.4 | Page 207

What are the oxidation states of phosphorus in the following:

Na3PO4

Q 31.5 | Page 207

What are the oxidation states of phosphorus in the following:

POF3

Q 32.1 | Page 208

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

Q 32.2 | Page 208

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

Q 33 | Page 208

How are xenon fluorides XeF2, XeF4 and XeF6 obtained?

Q 34 | Page 208

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

Q 35 | Page 208

How are XeO3 and XeOF4 prepared?

Q 36.1 | Page 208

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

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

Q 36.2 | Page 208

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

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

Q 37 | Page 208

Which one of the following does not exist?

(i) XeOF4

(ii) NeF2

(iii) XeF2

(iv) XeF6

Q 38.1 | Page 208

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

ICI_4^(-)

Q 38.2 | Page 208

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

IBr_2^(-)

Q 38.3 | Page 208

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

BrO_3^(-)

Q 39 | Page 208

Why do noble gases have comparatively large atomic sizes?

Q 40 | Page 208

List the uses of Neon and argon gases.

## NCERT solutions for Class 12 Chemistry chapter 7 - The p-block Elements

NCERT solutions for Class 12 Chemistry chapter 7 (The p-block Elements) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Class 12 Chemistry solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Class 12 Chemistry chapter 7 The p-block Elements are Concept of Group 15 Elements, Dinitrogen, Ammonia, Oxides of Nitrogen, Phosphorus - Allotropic Forms, Compounds of Phosphorus, Phosphine, Concept of Group 16 Elements, Dioxygen, Classification of Oxides, Simple Oxides, Ozone, Sulphur - Allotropic Forms, Compounds of Sulphur, Sulphur Dioxide, Sulphuric Acid, Oxoacids of Sulphur, Concept of Group 17 Elements, Compounds of Halogens, Chlorine, Hydrogen Chloride, Interhalogen Compounds, Oxoacids of Halogens, Concept of Group 18 Elements, Phosphorus Halides, Oxoacids of Phosphorus, Nitric Acid, P Block Elements.

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