Identifying Lewis Acids and Bases

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Ray Guo 4C
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Joined: Fri Sep 28, 2018 12:15 am

Identifying Lewis Acids and Bases

Postby Ray Guo 4C » Wed Dec 05, 2018 7:26 pm

Question 6.5 in 7th edition asks that, in the reaction between hydrogen peroxide H2O2 and sulfur trioxide SO3 to form H2SO5, which reactant is Lewis acid and which is base. Can anyone explain why SO2 is the acid and H2O2 the base?

Tiffany_Cacy_3D
Posts: 70
Joined: Fri Sep 28, 2018 12:24 am

Re: Identifying Lewis Acids and Bases

Postby Tiffany_Cacy_3D » Wed Dec 05, 2018 7:51 pm

I don't fully understand why SO3 is the base but when I draw the lewis structure you can see that there is resonance in its structure and in order to fill the octet rule the Sulfur in the center has to make one double bond. When you draw the lewis structure for H2O2 it is nicely balanced, it is non-polar and has no need for any extra electrons while SO3 on the other hand is ready to accept electrons. I am sure there are other contributing factors but that is what I observed from this problem.

Rachel Dang 1H
Posts: 32
Joined: Fri Sep 28, 2018 12:17 am

Re: Identifying Lewis Acids and Bases

Postby Rachel Dang 1H » Wed Dec 05, 2018 8:28 pm

This is a good question, can someone answer it?

Matthew Mar 1J
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Re: Identifying Lewis Acids and Bases

Postby Matthew Mar 1J » Thu Dec 06, 2018 8:22 pm

Maybe It's because SO3 has the option to include either single or double bonds? If all three oxygens are double bonded to the sulfur, the molecule is stable, but if it acts as an acid, some of the double bonds can switch to single bonds to create room to accept electrons. H2O2 on the other hand is stuck with its arrangement since hydrogen can't double bond, so it always has lone pairs on the oxygens open to donate to other molecules.


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