Acid/Base Trends

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DTingey_1C
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Joined: Fri Aug 30, 2019 12:16 am

Acid/Base Trends

Postby DTingey_1C » Thu Dec 05, 2019 1:01 pm

If the strength of binary acids increases with elements across a period because of the increase in electronegativity, why does the strength of binary acids also increase with elements down a group if electronegativity typically decreases down a group? Thanks

Veronica_Lubera_2A
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Re: Acid/Base Trends

Postby Veronica_Lubera_2A » Thu Dec 05, 2019 1:04 pm

Strong acids dissociate completely. When going down a group, the atoms are getting larger (making a bond longer), and therefore making the bond weaker. Therefore, the strength will increase because the bond is easier to break.

Rita Chen 1B
Posts: 112
Joined: Sat Jul 20, 2019 12:15 am

Re: Acid/Base Trends

Postby Rita Chen 1B » Thu Dec 05, 2019 1:05 pm

I think this is because as you go down a group for binary acids, you are looking at the strength and length of the HA bond, not the polarity, so the weaker the HA bond, the stronger the acid.

Annie Ye
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Re: Acid/Base Trends

Postby Annie Ye » Thu Dec 05, 2019 1:26 pm

Why is HF a weaker acid than HI?

Daniel Honeychurch1C
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Re: Acid/Base Trends

Postby Daniel Honeychurch1C » Thu Dec 05, 2019 1:29 pm

I has a larger ionic radius which makes the H-I bond longer and weaker. Therefore, HI dissociates more than HF and is a stronger acid.

andrewcj 2C
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Re: Acid/Base Trends

Postby andrewcj 2C » Thu Dec 05, 2019 1:45 pm

Annie Ye wrote:Why is HF a weaker acid than HI?

When an acid dissociates, the bond must be broken between the H+ and the conjugate base. If the bond is strong, which it is in the case of HF, this makes it harder and less of the acid dissociates, resulting in less H+ present in the resulting solution and a higher pH by definition of pH.

Annie Ye
Posts: 106
Joined: Wed Sep 18, 2019 12:22 am

Re: Acid/Base Trends

Postby Annie Ye » Sun Dec 08, 2019 5:19 pm

The trend of acidity increases from left to right across the periodic table but it decreases going from top to bottom.


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