NCERT Solutions for Class 12 Chemistry Chemistry Part-1 Chapter 7

The p-Block Elements Class 12

Chapter 7 The p-Block Elements Exercise Solutions

<< Previous Chapter 6 : General Principles and Processes of Isolation of Elements Next Chapter 8 : The d-and f-Block Elements >>

In text : Solutions of Questions on Page Number : 169

Q1 :  

Why are pentahalides more covalent than trihalides?


Answer :

In pentahalides, the oxidation state is +5 and in trihalides, the oxidation state is +3. Since the metal ion with a high charge has more polarizing power, pentahalides are more covalent than trihalides.

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Q2 :  

Why is BiH3the strongest reducing agent amongst all the hydrides of

Group 15 elements?


Answer :

As we move down a group, the atomic size increases and the stability of the hydrides of group 15 elements decreases. Since the stability of hydrides decreases on moving from NH3to BiH3, the reducing character of the hydrides increases on moving from NH3to BiH3.

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Q3 :  

Why is N2less reactive at room temperature?


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Q4 :  

Mention the conditions required to maximise the yield of ammonia.


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Q5 :  

How does ammonia react with a solution of Cu2+?


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Q6 :  

What is the covalence of nitrogen in N2O5?


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Q7 :  

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


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Q8 :  

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


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Q9 :  

What happens when PCl5is heated?


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Q10 :  

Write a balanced equation for the hydrolytic reaction of PCl5in heavy water.


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Q11 :  

What is the basicity of H3PO4?


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Q12 :  

What happens when H3PO3is heated?


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Q13 :  

List the important sources of sulphur.


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Q14 :  

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


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Q15 :  

Why is H2O a liquid and H2S a gas?


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Q16 :  

Which of the following does not react with oxygen directly?

Zn, Ti, Pt, Fe


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Q17 :  

Complete the following reactions:

(i) C2H4 + O2

(ii) 4Al + 3O2


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Q18 :  

Why does O3act as a powerful oxidising agent?


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Q19 :  

How is O3estimated quantitatively?


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Q20 :  

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


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Q21 :  

Comment on the nature of two S-O bonds formed in SO2molecule. Are the two S-O bonds in this molecule equal?


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Q22 :  

How is the presence of SO2detected?


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Q23 :  

Mention three areas in which H2SO4plays an important role.


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Q24 :  

Write the conditions to maximize the yield of H2SO4by Contact process.


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Q25 :  

Why is for H2SO4in water?


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Q26 :  

Considering the parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy, compare the oxidising power of F2and Cl2.


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Q27 :  

Give two examples to show the anomalous behaviour of fluorine.


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Q28 :  

Sea is the greatest source of some halogens. Comment.


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Q29 :  

Give the reason for bleaching action of Cl2.


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Q30 :  

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


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Q31 :  

Why is ICl more reactive than I2?


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Q32 :  

Why is helium used in diving apparatus?


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Q33 :  

Balance the following equation: XeF6+ H2O XeO2F2+ HF


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Q34 :  

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


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<< Previous Chapter 6 : General Principles and Processes of Isolation of Elements Next Chapter 8 : The d-and f-Block Elements >>

Exercise : Solutions of Questions on Page Number : 207

Q1 :  

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


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Q2 :  

Why does the reactivity of nitrogen differ from phosphorus?


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Q3 :  

Discuss the trends in chemical reactivity of group 15 elements.


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Q4 :  

Why does NH3form hydrogen bond but PH3does not?


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Q5 :  

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


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Q6 :  

How is ammonia manufactured industrially?


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Q7 :  

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


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Q8 :  

Give the resonating structures of NO2 and N2O5.


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Q9 :  

The HNH angle value is higher than HPH, HAsH and HSbH angles. Why? [Hint: Can be explained on the basis of sp3hybridisation in NH3and only s-p bonding between hydrogen and other elements of the group].


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Q10 :  

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


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Q11 :  

Explain why NH3is basic while BiH3is only feebly basic.


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Q12 :  

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


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Q13 :  

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


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Q14 :  

Why does nitrogen show catenation properties less than phosphorus?


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Q15 :  

Give the disproportionation reaction of H3PO3.


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Q16 :  

Can PCl5act as an oxidising as well as a reducing agent? Justify.


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Q17 :  

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.


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Q18 :  

Why is dioxygen a gas but sulphur a solid?


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Q19 :  

Knowing the electron gain enthalpy values for O → O-and O → O2-as -141

and 702 kJ mol-1respectively, 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).


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Q20 :  

Which aerosols deplete ozone?


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Q21 :  

Describe the manufacture of H2SO4by contact process?


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Q22 :  

How is SO2an air pollutant?


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Q23 :  

Why are halogens strong oxidising agents?


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Q24 :  

Explain why fluorine forms only one oxoacid, HOF.


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Q25 :  

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


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Q26 :  

Write two uses of ClO2.


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Q27 :  

Why are halogens coloured?


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Q28 :  

Write the reactions of F2and Cl2with water.


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Q29 :  

How can you prepare Cl2from HCl and HCl from Cl2? Write reactions only.


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Q30 :  

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


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Q31 :  

What are the oxidation states of phosphorus in the following:

(i) H3PO3 (ii) PCl3 (iii) Ca3P2

(iv) Na3PO4 (v) POF3?


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Q32 :  

Write balanced equations for the following:

(i) NaCl is heated with sulphuric acid in the presence of MnO2.

(ii) Chlorine gas is passed into a solution of NaI in water.


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Q33 :  

How are xenon fluorides XeF2, XeF4and XeF6obtained?


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Q34 :  

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


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Q35 :  

How are XeO3and XeOF4prepared?


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Q36 :  

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

(i) F2, Cl2, Br2, I2- increasing bond dissociation enthalpy.

(ii) HF, HCl, HBr, HI - increasing acid strength.

(iii) NH3, PH3, AsH3, SbH3, BiH3- increasing base strength.


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Q37 :  

Which one of the following does not exist?

(i) XeOF4 (ii) NeF2

(iii) XeF2 (iv) XeF6


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Q38 :  

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

(i)

(ii)

(iii)


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Q39 :  

Why do noble gases have comparatively large atomic sizes?


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Q40 :  

List the uses of Neon and argon gases.


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<< Previous Chapter 6 : General Principles and Processes of Isolation of Elements Next Chapter 8 : The d-and f-Block Elements >>

Chemistry Part-1 - Chemistry : CBSE NCERT Exercise Solutions for Class 12th for The p-Block Elements will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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