IIT JEE , AIEEE Forum - Chemistry , Inorganic Chemistry - Halogen oxyacids

samarthrvittal

1) is "thermal stability" the same as just "stability" ? if yes , then since "more acidic" means "less stable" , thermal stability of HClO4 should be low compared to HClO , but this is not the case.

2) how do u decide oxidising power ? eg- oxidising power of ClO- is more than ClO4- , but this seems illogical as ClO4- has so many "O"s to give away !

3) why is HI a stronger acid than HCl but oxyacids of Iodine weaker than the corresponding Chloro-oxyacids ?

all info courtesy OP Agarwal - JPNP. any answer with a semblance of correctness will be rated :) :) :) ty !

narulaajun

more acidic has got nothing to do with stability,,it justs reflects the ability of acid to donate proton

isnt ClO4^- better O.A than ClO-...coz its oxidation state of Cl in ClO4- is +7 which can down by self reduction

strength of acid as i said is ability to donate proton..since in HI the H-I bond is larger...its bond enthalpy is less, hence easier to ionize...releasing H+ easier..making it stronger acid

samarthrvittal

na, thats the point ! OP Agarwal says oxidising power decreases from ClO- to ClO4- ... which cant be true !

narulaajun

well a possible explanation could be that Cl exists in -1 OS more stable than ClO4- existing as some other OS

but im not 100%

dev_22oct

the greater the number of O atoms(ie the higher the oxidation state of halogen) in a series of oxoacids of a halogen the greater is the thermal stability.the activity of oxoacids as oxidising agent is inversly related to the number of O atoms or the oxidation state of halogen atom in the molecule. thus HCLO is the strongest oxidising agent and HClO₄ is the weakest oxidising agent. in other words, oxidising power is the greatest for acids of lower thermal stability.

dev_22oct

order of thermal stability is HClO>HClO₂>HClO₃>HClO4 its same as acidic nature.

order of oxidising strength is reverse.

dev_22oct

When we talk abt the thermal stability we consider ClO₄^-

ClO₃^- >ClO₂^- >ClO^-

and the reason is localization of -ve charge.

dev_22oct

HI is stronger acid than HCl is because of heat of ionisation which is large for HI(63.8KJ/MOL) compared to HCl(59.8kj/mol)

HEAT OF IONIZATION : the energy released in ionization of 1 MOLE HX (X=HALOGEN)

HClO3 is stronger acid than HIO3 because as the electronegativity of the central atom X decreases as we move from CL to I , the tendency of the central atom to attract the electron pair of X-O bond towards itself decreases and hence the possibility of rupture of O-H bond decreases.

narulaajun

y is there release of energy in ionization,,,which requires energy rather than it being released

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