Strength of an acid

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Simrina Desar Dis 1H
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Joined: Fri Sep 29, 2017 7:04 am

Strength of an acid

Postby Simrina Desar Dis 1H » Sat Dec 09, 2017 9:28 pm

How does electronegativity affect the relative strength of an acid?

Sabah Islam 1G
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Re: Strength of an acid

Postby Sabah Islam 1G » Sat Dec 09, 2017 9:36 pm

Electronegativity affects the relative strength of an acid because the more electronegative an atom is, the more likely it wants to "hold on" to the hydrogen atom attached to it, therefore making it harder for the acid to deprotonate and for the H+ ion to detach from it. For example, comparing HF and HCl, fluoride is more electronegative, so it is stronger in holding to the hydrogen atom, but chloride is less electronegative, so it would be easier to pull the H+ ion away for it than it would be from the fluoride.

804899546
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Re: Strength of an acid

Postby 804899546 » Sat Dec 09, 2017 9:39 pm

Then how come HF is a stronger base than HOH, even though fluorine is more electronegative than oxygen? Does the strength of an acid increase as we go across the periodic table?

Michelle Steinberg2J
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Re: Strength of an acid

Postby Michelle Steinberg2J » Sat Dec 09, 2017 10:00 pm

So acids with longer bonds are stronger than ones with shorter bonds? For example, HCl has a longer bond than HF, but is stronger?

fara valdez
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Re: Strength of an acid

Postby fara valdez » Sun Jun 03, 2018 11:10 pm

I think it relies on which bond is the most electronegative.

fara valdez
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Re: Strength of an acid

Postby fara valdez » Sun Jun 03, 2018 11:11 pm

Im also interested in that question: is it standard that acids with longer bonds are stronger?

EllenRenskoff-1C
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Re: Strength of an acid

Postby EllenRenskoff-1C » Wed Jun 06, 2018 5:27 pm

For an oxoacid, the rules would be slightly different as it is dependent on if the resulting anion is stabilized by delocalizing the negative charge. Basically, if the compound is Cl-O-H, it will be more acidic than I-O-H because it is more stabilized.The Cl is more electronegative than I, so it pulls more electrons away from the O than does the I. This would stabilize the charge more in the respective compound. So in this case, the rule regarding longer bonds being stronger acids does not necessarily apply because in the presence of oxygen, the strength of the acid is more dependent on the stability of the negative charge than the bond length.

RubyLake1F
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Re: Strength of an acid

Postby RubyLake1F » Fri Jun 08, 2018 5:00 pm

Why is it a rule that the more electronegative an atom is that is attached to hydrogen, the stronger the acid (in reference to molecules like HCl vs. H2S)? This seems counterintuitive, because a higher electronegativity difference should mean a more ionic and therefore a stronger bond.

204917020
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Re: Strength of an acid

Postby 204917020 » Sun Jun 10, 2018 9:13 pm

Strong acids and bases completely dissociate in solution. Therefore, they must have a small change in electronegativity between atoms in order for the molecule to completely dissociate in solution. On the other hand, weak acids and bases may partially dissociate in solution, but they do not completely dissociate.

Shione Nakahara 1F
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Re: Strength of an acid

Postby Shione Nakahara 1F » Sun Jun 10, 2018 9:42 pm

As you go down the group of the periodic table, acidity increases with the decrease of electronegativity (since the size of the atom increases). The smaller the atom, the shorter the bond and thus harder for them to dissociate in water. In my notes from class it says that HF<HCl<HBr<HI which goes from less acidic (short, strong bond) to more acidic (long, weaker bond).

Yixiao Hu 3C
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Re: Strength of an acid

Postby Yixiao Hu 3C » Sat Dec 01, 2018 1:23 pm

higher electronegativity difference means stronger acids (imagine H2S and HF)

105002507
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Re: Strength of an acid

Postby 105002507 » Sun Dec 02, 2018 1:05 pm

The higher the electronegativity difference, the stronger the acid

Hilda Sauceda 3C
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Re: Strength of an acid

Postby Hilda Sauceda 3C » Sun Dec 02, 2018 2:33 pm

Across a row in periodic table, acidity increases with the increase in electronegativity.

Jocelyne Milke 1G
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Re: Strength of an acid

Postby Jocelyne Milke 1G » Sun Dec 02, 2018 4:51 pm

The more electronegative an atom, the more willing it is to hold onto the electrons left over when the Hydrogen leaves the molecule.

ChemSection3I
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Re: Strength of an acid

Postby ChemSection3I » Wed Dec 05, 2018 4:57 pm

I was also wondering this, thanks for clarifying!


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