Fluorine cannot be prepared by heating NaF and MnO2 with conc. H2SO4 why?
Fluorine being the most electronegative element, MnO2 and H2SO4 are not able to oxidise F- to fluorine.
Why covalent bonds in halogens are always sigma bonds in nature?
The elements of the halogen family have ns2 np5 configuration of the valence shell. Thus, they have only one partially filled p-orbital present in the valence shell and the axial overlap of two partially filled orbitals of the two halogen atoms results in the formation of an o-bond.
What happens when fluorine gas is bubbled through a dilute solution of an alkali?
                2 NaOH+2F2    ž     (Cold)      2 NaF +OF2+H2O
Fluorine forms no compound analogous to HClO4.
                Being more electronegative than oxygen, Fluorine forms a weak bond with oxygen. Also because of its small size, it cannot form a compound analogue to Cl2O7.
Which member of the halogen family is most expected to exhibit positive oxidation state and why?
                Iodine is most expected to exhibit positive oxidation states because in moving down the group. Ionisation potential goes on decreasing and hence, tendency to form positive ions increases down the group.
CF4 and SF4 are not is structural.
                In CF4, carbon is sp3 hybridised. Thus, CF4 has tetrahedral shape. In SF4, sulphur is sp3 d-hybridised. Thus, SF4 has distorted trigonal bipyramidal shape in which one position is occupied by a lone pair.
Explain why AgBr is insoluble in water but soluble in Na2S2O3. Explain by writing equation.
                AgBr is insoluble in water due to its higher lattice energy. If dissolves in hypo due to the formation of a water soluble complex.
                AgBr + 2N2S2O3žNa3[Ag(S2O3)2] +NaBr.      Sod. Argento thiosulphate.
IF7 exists but BrF7 does not. Explain.
Iodine forms IF7 due to large size of central iodine atom. But BrF7 does not exist because seven fluorine atoms cannot be coordinated to relatively small bromine atom.
Why hydrofluoric acid is the weakest of all halogen acids?
Hydrofluoric acid exists in the form of associated molecules due to hydrogen bonding. Thus, due to thus, hydrogen ions are less available in solution.
Why cannot fluorides be oxidised to fluorine except by electrolysis?
                Fluorine being the strongest oxidising agent, fluorides cannot be oxidised to fluorine except by electrolysis.
Why do halogens exist as diatomic molecules?
                Each halogen atom has seven valence electrons and has a strong tendency to acquire one more electrons for stable configuration. Thus, each atom mutually shares one electron and form diatomic molecules.
Potassium hydrogen fluoride is a stable compound but KHCl2 is not. Explain.
                Due to high electro negativity of fluorine, HF forms hydrogen bond with F- ions and exists as HF2- ions. Due to this, KHF2 is formed. On the other hand, HCl does not form hydrogen bonds and HCl2- is not formed.


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