Determining Acid Strength

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Taizha 1C
Posts: 36
Joined: Fri Apr 06, 2018 11:01 am

Determining Acid Strength

Postby Taizha 1C » Sun Jun 10, 2018 8:26 pm

How would i determine the differences in strengths of acids? or how would i rank the acids? Would i determine the strength based on which is most acidic and which is the most electronegative?

...or does anyone have any recommendations to do this?

Chris Fults 1C
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Joined: Wed Nov 15, 2017 3:01 am

Re: Determining Acid Strength

Postby Chris Fults 1C » Sun Jun 10, 2018 8:48 pm

The bond strength of an acid generally depends on the size of the 'A' atom: the smaller the 'A' atom, the stronger the H-A bond. HF has the strongest bond and is the weakest acid. The strong bond between the more similarly-sized HF atoms doesn't want to break and allow the H to transfer. In contrast, HI is a very strong acid as Iodine has a very large atomic radius while H has a very small one. Therefore, HI has a greater proton transferer making it a stronger acid.

Alejandro Salazar 1D
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Joined: Fri Sep 29, 2017 7:05 am

Re: Determining Acid Strength

Postby Alejandro Salazar 1D » Sun Jun 10, 2018 9:38 pm

I would recommend memorizing the 7 common strong acids, which are HCI, HBr, HI, HNO3, HCIO3, HCIO4, H2SO4

Taizha 1C
Posts: 36
Joined: Fri Apr 06, 2018 11:01 am

Re: Determining Acid Strength

Postby Taizha 1C » Sun Jun 10, 2018 9:57 pm

Alejandro Salazar 1D wrote:I would recommend memorizing the 7 common strong acids, which are HCI, HBr, HI, HNO3, HCIO3, HCIO4, H2SO4


Are those acids already ranked from strongest to weakest? For example, HCl > HBr > HI ......?

Chem_Mod
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Re: Determining Acid Strength

Postby Chem_Mod » Sun Jun 10, 2018 10:02 pm

You have to know how to determine it from given the formula (because 1. H is loosely held, 2. the conjugate base formed stabilizes the negative charge better). Or you can compare it using Ka or pKa values.

Ashley Martinez 1G
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Joined: Fri Apr 06, 2018 11:03 am

Re: Determining Acid Strength

Postby Ashley Martinez 1G » Sun Jun 10, 2018 10:07 pm

It might also be helpful to note acid strength can also help determine base characteristics. For example, the stronger the acid, the weaker its conjugate base. The weaker a conjugate acid, the stronger the base.

Nimrat Brar 1E
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Re: Determining Acid Strength

Postby Nimrat Brar 1E » Sun Jun 10, 2018 11:37 pm

Taizha 1C wrote:
Alejandro Salazar 1D wrote:I would recommend memorizing the 7 common strong acids, which are HCI, HBr, HI, HNO3, HCIO3, HCIO4, H2SO4


Are those acids already ranked from strongest to weakest? For example, HCl > HBr > HI ......?


No, these strong acids go in the order of HI > HBr > HCl > HF. HI is the strongest acid.


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