H-F, H-Cl, H-Br, and H-I

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Michelle N - 2C
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Joined: Wed Sep 18, 2019 12:19 am

H-F, H-Cl, H-Br, and H-I

Postby Michelle N - 2C » Mon Dec 02, 2019 2:05 pm

I'm a little confused about what Dr. Lavelle was talking about today (Monday, December 2nd) about how despite what we know about

H - F
H -- Cl
H --- Br
H ---- I

H-F is the weakest of something? My apologies if this is very out of context, but can someone help me out on this? I'd very much appreciate it.

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Re: H-F, H-Cl, H-Br, and H-I

Postby xenamclean_1G » Mon Dec 02, 2019 2:49 pm

H-F was the weakest acid because it has the shortest, strongest bond. The acids get stronger down that list (the longer the bond gets.)

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Re: H-F, H-Cl, H-Br, and H-I

Postby Christineg1G » Mon Dec 02, 2019 3:01 pm

Remember that bond length increases with atomic radius. So, the longer the bond is between two elements, the stronger the acid is. For example, H-I has the longest bond, so it will be the strongest acid. And vice versa, the shorter the bond is, the weaker the acid is. So, H-F would be the weakest acid out of the ones you listed since it has the shortest bond.
Hope this helps!

Paul Hage 2G
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Joined: Thu Jul 25, 2019 12:17 am

Re: H-F, H-Cl, H-Br, and H-I

Postby Paul Hage 2G » Mon Dec 02, 2019 3:08 pm

Acid strength is based on how easily the molecule can give off a proton. Because HF has the shortest and therefore strongest bond, it would be somewhat difficult to break the H+ off the molecule, whereas the relatively long bonds in HCl, HBr, and HI make it easier for the molecules to give off a proton in solution.

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