Page 1 of 1

Determining Acid Strength

Posted: Sun Jun 10, 2018 8:26 pm
by Taizha 1C
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?

Re: Determining Acid Strength

Posted: Sun Jun 10, 2018 8:48 pm
by Chris Fults 1C
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.

Re: Determining Acid Strength

Posted: Sun Jun 10, 2018 9:38 pm
by Alejandro Salazar 1D
I would recommend memorizing the 7 common strong acids, which are HCI, HBr, HI, HNO3, HCIO3, HCIO4, H2SO4

Re: Determining Acid Strength

Posted: Sun Jun 10, 2018 9:57 pm
by Taizha 1C
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 ......?

Re: Determining Acid Strength

Posted: Sun Jun 10, 2018 10:02 pm
by Chem_Mod
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.

Re: Determining Acid Strength

Posted: Sun Jun 10, 2018 10:07 pm
by Ashley Martinez 1G
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.

Re: Determining Acid Strength

Posted: Sun Jun 10, 2018 11:37 pm
by Nimrat Brar 1E
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.