ncert solutions class 12 chemistry chapter 7 p block elements

ncert solutions class 12 chemistry chapter 7 p block elements

Intext questions

• 7.1 Why are pentahalides more covalent than trihalides ? 
• 7.2 Why is BiH3 the strongest reducing agent amongst all the hydrides of Group 15 elements ? 
• 7.3 Why is N2 less reactive at room temperature? 
• 7.4 Mention the conditions required to maximise the yield of ammonia. 
• 7.5 How does ammonia react with a solution of Cu2+? 
• 7.6 What is the covalence of nitrogen in N2O5 ? 
• 7.7 Bond angle in PH4+ is higher than that in PH3. Why?
• 7.8 What happens when white phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO2 ? 
• 7.9 What happens when PCl5 is heated? 
• 7.10 Write a balanced equation for the hydrolytic reaction of PCl5 in heavy water. 
• 7.11 What is the basicity of H3PO4? 
• 7.12 What happens when H3PO3 is heated? 
• 7.13 List the important sources of sulphur.
• 7.14 Write the order of thermal stability of the hydrides of Group 16 elements. 
• 7.15 Why is H2O a liquid and H2S a gas ? 
• 7.16 Which of the following does not react with oxygen directly? Zn, Ti, Pt, Fe 
• 7.17 Complete the following reactions: (i) C2H4 + O2 → (ii) 4Al + 3 O2 → 
• 7.18 Why does O3 act as a powerful oxidising agent? 
• 7.19 How is O3 estimated quantitatively? 
• 7.20 What happens when sulphur dioxide is passed through an aqueous solution of Fe(III) salt? 
• 7.21 Comment on the nature of two S–O bonds formed in SO2 molecule. Are the two S–O bonds in this molecule equal ? 
• 7.22 How is the presence of SO2 detected ? 
• 7.23 Mention three areas in which H2SO4 plays an important role. 
• 7.24 Write the conditions to maximise the yield of H2SO4 by Contact process. 
• 7.25 Why is a2 a1 K << K for H2SO4 in water ? 
• 7.26 Considering the parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy, compare the oxidising power of F2 and Cl2. 
• 7.27 Give two examples to show the anomalous behaviour of fluorine. 
• 7.28 Sea is the greatest source of some halogens. Comment. 
• 7.29 Give the reason for bleaching action of Cl2. 
• 7.30 Name two poisonous gases which can be prepared from chlorine gas. 
• 7.31 Why is ICl more reactive than I2? 
• 7.32 Why is helium used in diving apparatus? 
• 7.33 Balance the following equation: XeF6 + H2O → XeO2F2 + HF 
• 7.34 Why has it been difficult to study the chemistry of radon? 

ncert solutions class 12 chemistry chapter 7 p block elements

Excercise Problems

• 7.1 Discuss the general characteristics of Group 15 elements with reference totheir electronic configuration, oxidation state, atomic size, ionisation enthalpyand electronegativity. 
• 7.2 Why does the reactivity of nitrogen differ from phosphorus? 
• 7.3 Discuss the trends in chemical reactivity of group 15 elements. 
• 7.4 Why does NH3 form hydrogen bond but PH3 does not? 
• 7.5 How is nitrogen prepared in the laboratory? Write the chemical equationsof the reactions involved. 
• 7.6 How is ammonia manufactured industrially? 
• 7.7 Illustrate how copper metal can give different products on reaction with HNO3. 
• 7.8 Give the resonating structures of NO2 and N2O5.
•  7.9 The HNH angle value is higher than HPH, HAsH and HSbH angles. Why?[Hint: Can be explained on the basis of sp3hybridisation in NH3 and onlys–p bonding between hydrogen and other elements of the group]. 
• 7.10 Why does R3P = O exist but R3N = O does not (R = alkyl group)? 
• 7.11 Explain why NH3 is basic while BiH3 is only feebly basic. 
• 7.12 Nitrogen exists as diatomic molecule and phosphorus as P4. Why? 
• 7.13 Write main differences between the properties of white phosphorus and redphosphorus. 
• 7.14 Why does nitrogen show catenation properties less than phosphorus? 
• 7.15 Give the disproportionation reaction of H3PO3. 
• 7.16 Can PCl5 act as an oxidising as well as a reducing agent? Justify. 
• 7.17 Justify the placement of O, S, Se, Te and Po in the same group of theperiodic table in terms of electronic configuration, oxidation state and hydrideformation. 
• 7.18 Why is dioxygen a gas but sulphur a solid? 
• 7.19 Knowing the electron gain enthalpy values for O → O– and O → O2– as –141and 702 kJ mol–1 respectively, how can you account for the formation of alarge number of oxides having O2– species and not O–?(Hint: Consider lattice energy factor in the formation of compounds). 
• 7.20 Which aerosols deplete ozone? 
• 7.21 Describe the manufacture of H2SO4 by contact process?
• 7.22 How is SO2 an air pollutant? 
• 7.23 Why are halogens strong oxidising agents?
• 7.24 Explain why fluorine forms only one oxoacid, HOF. 
• 7.25 Explain why inspite of nearly the same electronegativity, oxygen formshydrogen bonding while chlorine does not.
• 7.26 Write two uses of ClO2.
• 7.27 Why are halogens coloured? 
• 7.28 Write the reactions of F2 and Cl2 with water.
• 7.29 How can you prepare Cl2 from HCl and HCl from Cl2? Write reactions only. 
• 7.30 What inspired N. Bartlett for carrying out reaction between Xe and PtF6? 
• 7.31 What are the oxidation states of phosphorus in the following:(i) H3PO3 (ii) PCl3 (iii) Ca3P2 (iv) Na3PO4 (v) POF3? 
• 7.32 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.
•  7.33 How are xenon fluorides XeF2, XeF4 and XeF6 obtained? 
• 7.34 With what neutral molecule is ClO– isoelectronic? Is that molecule a Lewisbase? 
• 7.35 How are XeO3 and XeOF4 prepared? 
• 7.36 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. 
• 7.37 Which one of the following does not exist?(i) XeOF4 (ii) NeF2 (iii) XeF2 (iv) XeF6 
• 7.38 Give the formula and describe the structure of a noble gas species whichis isostructural with:(i) ICl4– (ii) IBr2– (iii) BrO3– 
• 7.39 Why do noble gases have comparatively large atomic sizes? 
• 7.40 List the uses of neon and argon gases.