Weak base-strong acid

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BrianaBarr2A
Posts: 22
Joined: Wed Sep 21, 2016 3:00 pm

Weak base-strong acid

Postby BrianaBarr2A » Wed Nov 30, 2016 2:45 pm

I'm really lost on where the third reaction comes from when writing the chemical reactions like what we did in class today. Can someone explain to me why its there and how we get it?

Jessica Chern 1H
Posts: 22
Joined: Sat Jul 09, 2016 3:00 am

Re: Weak base-strong acid

Postby Jessica Chern 1H » Wed Nov 30, 2016 4:10 pm

It's basically showing why the stoichiometric point is not exactly at ph7 for weak acids or bases.

NH3 + HCl + H2O <-> H2O + NH4+ + Cl-

^This part shows how the salt donates its proton to the base, forming a conjugate acid (NH4+). Since it's a weak base, it's at an equilibrium, so that some of the conjugate acid will also donate a proton and become the original base (NH3).

H2O + NH4+ + Cl- <-> NH3 + H3O+ + Cl-

^This is just showing how the conjugate acid donates a proton and thus becomes the original base. Water accepts that proton to become a hydronium ion, which increases the acidity of the overall solution and decreases the pH.

Hope that makes sense!


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