HCl vs. HI

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HCl vs. HI

Postby Meachelle_Lum_1I » Thu Dec 06, 2018 3:05 am

HI is a stronger acid because H and I have a longer/weaker bond and the H+ ions will thus dissociate more, resulting in a stronger acid. However, Cl is more electronegative (another stronger acid property).

So in determining the strength of an acid, does bond length trump electronegativity?

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Re: HCl vs. HI

Postby AhYeon_Kwon_2H » Thu Dec 06, 2018 3:18 am

I think so, since the key concept is that strong acids lose H+ easily, and weaker bonds lead to more acidity. Electronegativity seems to be more relevant for other examples, like hypochlorous acid vs. hypoiodous acid, where Cl's higher electronegativity stabilizes oxygen and makes hypochlorous acid more acidic.

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Re: HCl vs. HI

Postby Nicolette_Canlian_2L » Thu Dec 06, 2018 3:33 am

You can also determine this based on the atomic radius. Since I has a larger atomic radius than Cl, it is easier for the I atom to release H+ than it is for Cl because of the looser pull of the electrons towards the central atom.

Carlos De La Torre 2L
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Re: HCl vs. HI

Postby Carlos De La Torre 2L » Thu Dec 06, 2018 4:27 pm

electronegativity only matters for molecules, not single atom ions, because the higher electronegativity will help spread the negative charge over a higher area and thus will make it more stable but electronegativity doesn't matter for single atom ions because regardless of the electronegativity the charge will only be on one atom.

Pritish Patil 1K
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Re: HCl vs. HI

Postby Pritish Patil 1K » Fri Dec 07, 2018 11:10 am

Whichever atom has a higher atomic radius means that there will be a longer bond, therefore a stronger acid because more H+ can disassociate easier.

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Re: HCl vs. HI

Postby 105002507 » Fri Dec 07, 2018 7:58 pm

the larger the atomic radius indicates a longer bond and stronger acid

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Re: HCl vs. HI

Postby 305117729 » Fri Dec 07, 2018 9:28 pm

When evaluating acidity, it's more likely to consider the extent of dissociation of acids in water, which means if an acid gives more H+ ions it will be stronger, so we will see HI as the stronger acid as the HI bond is weaker and it will give more H+ ions.

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Re: HCl vs. HI

Postby Raphael_SanAndres3C » Fri Dec 07, 2018 9:31 pm

I think bond length and electronegativity are directly related since the more electronegative an ion is, the shorter the bond length, the less acidic it is.

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