BF3 is a Lewis Acid, right?

[mr chievous]

If it's an acid, it should decrease the pH, correct? How exactly would it do that since it has no Hs?

Super basic question, but I can't seem to figure it out.

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[NuttyEngDude]

check this out:
http://www.uiowa.edu/~c004121/notes/ch02_3.pdf
bottom of page nine, looks like the attached thumbnail. I presume the H+ will eventually be taken by another water molecule to stabilize the O+

 

[cheesier]

Lewis acids or bases (always?) turn into bronsted lowry acids or bases in water, so BF3 turns into HBF4 and B(OH)3. HBF4 is a bronsted lowry acid and B(OH)3 which reacts to form B(OH)4 and H+.

 

[gettheleadout]

Lewis acids or bases (always?) turn into bronsted lowry acids or bases in water, so BF3 turns into HBF4 and B(OH)3. HBF4 is a bronsted lowry acid and B(OH)3 which reacts to form B(OH)4 and H+.

How did you know that?

Edit: This specific reaction I mean. I would have just assumed that as a Lewis acid BF3 would accept an H2O and then lose the proton to stabilize the oxygen, thus lowering pH. The outcome is the same for solution acidity but how the heck did you know this particular pathway?

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[cheesier]

How did you know that?

Edit: This specific reaction I mean. I would have just assumed that as a Lewis acid BF3 would accept an H2O and then lose the proton to stabilize the oxygen, thus lowering pH. The outcome is the same for solution acidity but how the heck did you know this particular pathway?

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I had the same question awhile ago and looked it up. If you know that lewis acids turn into bronsted lowry acids you could reason it out too. BF3 has to turn into an H+ donating species before it can increase H+ in solution, and HBF3 whould have a charge, so it would have to be HBF4.

 

[gettheleadout]

I had the same question awhile ago and looked it up. If you know that lewis acids turn into bronsted lowry acids you could reason it out too. BF3 has to turn into an H+ donating species before it can increase H+ in solution, and HBF3 whould have a charge, so it would have to be HBF4.

I didn't know that either haha I would have just assumed it abstracted OH- from water and left it at that.