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Question

  Give reason for the below
1))all bonds in pcl5are not equivalent. 
2)ka2<<ka1for h2so4in water
3)inter halogen compounds are strong oxidising agents 
4)the bond energy of F2 is less than that of cl2
5) of the Nobel gases only Xenon forms known chemical compounds


Solution

1).

PCl5 has a trigonal bipyramidal structure due to the dsp3 hybridization. Due to this trigonal bipyramidal structure, the 2wo Cl-atoms of PCl5 molecule are stretched at the axis and become little longer and so called as axial bonds, while the rest three Cl-atoms lie on the equator and called as equatorial bonds.

We know, that the axial bonds are more stretched and longer than equatorial bonds so, the three equatorial Cl-atoms become equivalent and the two axial Cl-atom become equivalent while, both the groups are not identical which makes the difference in bonding of PCl5 molecule.

2).

Ka1 is when H2SO4 gives HSO4- and H+.

Ka2 is when HSO4- gives SO42- and H+.

It is much easier for a neutral H2SO4 to release H+ than a negatively charged HSO4-. Hence Ka2 is much lesser than Ka1.

3).Interhalogen compounds are stronger oxidising agent because these are essentially covalent compounds having weak bond strengths due to bonding between two dissimilar electronegative elements. This increases their reactivity. Since they consists of only halogen atoms which are electronegative, hence they easily accept electrons from other elements and oxidise them.

4).Fluorine (F2), Chlorine (Cl2) and Bromine (Br2), all have three lone pair of electrons on each atom of Fluorine, chlorine and Bromine atoms. The size of fluorine is smaller than Chlorine and bromine. Due to which there is higher electron density on Fluorine. Due to smaller size and higher electron density there is repulsion between the electrons which is known as interelectronic repulsion. Due to this repulsion between the electrons both the atoms want to move apart. Hence the bond can be cleaved easily and the bond dissociation energy is less.

5).Due to large atomic size, the first IE for xenon is low as compared to IE of the other elemnts of the group. Hence, even though having a stable electonic configuration, the outer most shell electrons experience less attraction to the nucleus and hence can participate in bonding with other elements when sufficient energy is provided.

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