Terri asked in Science & MathematicsChemistry · 2 years ago

# B(OH)4- + H2O <--> H3BO3 + ? I think it is OH- but I'm not sure and I need to understand how to work through it. Thank you?

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• Anonymous
2 years ago

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• 2 years ago

I agree that it doesn't look right, which is part of what is confusing to me, however on rechecking, it is shown in book exactly as stated in the question @pisgahchemist under the topic of Hydrolysis Equilibria, reading through your explanation makes sense though, that it is indeed OH-, so thank you, I get it now :)

• 2 years ago

Boric acid, H3BO3.....

Boric acid is also written as B(OH)3, which looks like the formula of a base.

HO − B − OH

..........|

.........OH

The most common description of boric acid's acidic behavior is this: When boric acid reacts with water, an OH- from water combines with B(OH)3 to make B(OH)4^- and leaves a hydrogen ion (H+) in solution, making the solution acidic. So boric acid does not "donate" a proton. The proton which makes the solution acidic comes from water.

B(OH)3(aq) + HOH(l) <==> H+ + B(OH)4^- ................ Ka = 7.3x10^-10

There are other sources which suggest that boric acid is a more "normal" proton donating acid.

H3BO3 --> H+ + H2BO3^- ...... Ka = 5.8x10^-10

As for your equation, I don't think you have it quite right. It could be:

B(OH)4^- + H+ <==> H3BO3 + HOH

• Jan
Lv 7
2 years ago

B(OH)4^-<--> H3BO3 + OH^-