Is sulfur dioxide a lewis acid or base?

[flodhi1]

So for some reason in the reaction between So2 + H29 --> H2SO3
The Berkley review book says that So2 is the lewis acid. So technically it's saying that the sulfur is accepting electrons. Is that possible considering that S would have lone pairs on it in the So2 structure. Thus wouldn't it be tempting to think of it as the lewis base?
Then it says that metal oxides are lewis bases? lol wtf dude seriously

Okay my attempt to understand this:-

1) I think that okay metals tend to lose electrons to they can form cations thus they would be electron donors/ oxidized and i guess Lewis bases.
2) Non metals tend to accept electrons to fill their octets such as Chlorine needs 1 valence electron. Thus accepting would be reduced and i guess lewis acid?

---

Members don't see this ad.

 

[Rabolisk]

There is nothing "lol wtf dude seriously" about this. Simply put, metal oxides tend to behave as lewis bases while nonmetal oxides (covalent oxides) tend to be lewis acids. Compare their reaction with a single reagent, water.

SO2 + H2O yields H2SO3. The lone pair on the water oxygen attacks sulfur, forming an O-S bond. Thus H2O acts as the lewis base and SO2 as the lewis acid.

CaO + H2O yields Ca(OH)2. The lone pair on the calcium oxide oxygen attacks the water hydrogen. Thus CaO acts as the lewis base and H2O as the lewis acid.

This shouldn't be surprising, since oxyacids (sulfuric acid, phosphoric acid, perchloric acid, etc.) are formed by reacting nonmetal oxides with water, and strong basic hydroxides (NaOH, KOH, etc.) are formed by reacting metal oxides with water.

I wouldn't worry about oxidation/reduction. There is no redox when metal or nonmetal oxides react with water.

 

[BerkReviewTeach]

Really well put Rabolisk!