Q24 of 22 Page 1

(a) Account for the following:

(i) Acidic character increases from HF to HI.


(ii) There is a large difference between the melting and boiling points of oxygen and sulphur.


(iii) Nitrogen does not form pentahalide.


(b) Draw the structures of the following:


(i) ClF3 (ii) XeF4


OR


(i) Which allotrope of phosphorus is reactive and why?


(ii) How are the supersonic jet aeroplanes responsible for the depletion of ozone layer?


(iii) F2 has lower bond dissociation enthalpy than Cl2. Why?


(iv) Which noble gas is used in filling balloons for meteorological observations?


(v) Complete the following equation: XeF2 + PF5 →


(a)


(i) Acidic character increases from HF to HI because the size increases in going from F to I due to which the bond strength between Hydrogen and halogen decreases, thereby, increasing acidity.


Order of bond strength: HF> HCl> HBr> HI


Order of acidity: HF< HCl< HBr< HI.


(ii) Sulphur exists as S8 i.e. polyatomic molecule and Oxygenexists as O2 i.e. diatomic molecule. So that’s why sulphur melts and boils at high melting and boiling point respectively and thus, there is a large difference between their melting and boiling points.


(iii) Nitrogen does not form pentahalide because nitrogen does not have d orbitals so its covalency is restricted maximum to 4 as only $ orbitals are available for bonding.


(b)


(i) ClF3


Shape: bent T



(ii) XeF4


Shape: square planar



OR


(i) White phosphorus is most reactive form of phosphorus because it exists as discrete tetrahedra with bond angle 60° because of which there is angular strain and hence it is more reactive than other forms of phosphorus.



(ii) The exhaust emitted from supersonic jet aeroplane contains CO2, NO, by-products of petrochemicals, and other particles which reacts with ozone layer and are the reason for depletion of stratospheric ozone layer.


(iii) F2 has lower bond dissociation enthalpy than Cl2 due to smaller size and higher electronegativity of F, repulsion between the F-F electrons occur and both the atoms want to move apart. Hence the bond can be cleaved easily.


(iii) Noble gas used in filling balloons for meteorological observations is Helium (He) because it is non- inflammable and lightweight.


(iv) Xenon fluorides react with fluoride ion acceptors to form cationic species and fluoride ion donors to form fluoroanions.


XeF2 + PF5 → [XeF]+[PF6]-


More from this chapter

All 22 →
22

Write the names and structures of the monomers of the following polymers:

(i) Terylene


(ii) Buna-S


(iii) Neoprene


 23

Seeing the growing cases of diabetes and depression among young children, Mr. Chopra, the principal of one reputed school organized a seminar in which he invited parents and principals. They all resolved this issue by strictly banning junk food in schools and introducing healthy snacks and drinks like soup, lassi, milk, etc. in school canteens. They also decided to make compulsory half an hour of daily physical activities for the students in the morning assembly. After six months, Mr. Chopra conducted the health survey in most of the schools and discovered a tremendous improvement in the health of the students.

After reading the above passage, answer the following questions:


(i) What are the values (at least two) displayed by Mr. Chopra? (ii) As a student, how can you spread awareness about this issue? (iii) Why should antidepressant drugs not be taken without consulting a doctor? (iv) Give two examples of artificial sweeteners.


 25

An aromatic compound ‘A’ of molecular formula C7H6O2 undergoes a series of reactions as shown below. Write the structures of A, B, C, D and E in the following reactions:


OR


(a) Write the structures of main products when benzene diazonium chloride reacts with the following reagents:


(i) H3PO2 + H2O


(ii) CuCN/KCN


(iii) H2O


(b) Arrange the following in the increasing order of their basic character in an aqueous solution: C2H5NH2, (C2H5)2NH, (C2H5)3N


(c) Give a simple chemical test to distinguish between the following pair of compounds: C6H5-NH2 and C6H5-NH-CH3.


 26

For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained:

t/s 0 10 20


[CH3COOCH3]/mol L-1 0.10 0.05 0.025


(a) Show that it follows pseudo first order reaction, as the concentration of water remains constant.


(b) Calculate the average rate of reaction between the time intervals 10 to 20 seconds. (Given: log 2 = 0.3010, log 4 = 0.6021)


OR


(a) For a reaction A + B → P, the rate is given by


Rate = k [A][B]2


(i) How is the rate of reaction affected if the concentration of B is doubled? (ii) What is the overall order of reaction if A is present in large excess?


(b) A first order reaction takes 30 minutes for 50% completion. Calculate the time required for 90% completion of this reaction.