lecture 19.5- buffers & salts honors
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Lecture 19.5 for Honors ChemistryTRANSCRIPT
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19.3
Previously, on HCHEM….
THE LARGER THE Ka THE STRONGERTHE ACID!!
The larger the Kb the more dissociationoccurs, so the stronger the base.
The conjugates of weak acids & basesare strong.
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Salts can be acidic or basic if one of theions is a conjugate of something weak.
19.5
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Salts can be acidic or basic if one of theions is a conjugate of something weak.
Ex.NH4Cl is an acidic salt because NH4
+ isthe conjugate of a weak base.
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Salts can be acidic or basic if one of theions is a conjugate of something weak.
Ex.NH4Cl is an acidic salt because NH4
+ isthe conjugate of a weak base.
NaCH3COO is a basic salt becauseCH3COO- is the conjugate of a weakacid
19.5
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To determine whether a salt solution is acidicor basic, remember the following rules:
Not because the strong ones give more ions.
In a neutralization weak acids and bases will give allof their ions because they are neutralized. (shiftsequilibrium towards dissociation)
It is because of the acid/base properties of theconjugates.
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Would the following salts create acidicor basic solutions when dissolved inwater?
NaClKC2H3O2
NH4NO3
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Would the following salts create acidicor basic solutions when dissolved inwater? cation anion
from base from acidNaCl weak weakKC2H3O2 weak basicNH4NO3 acidic weak
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Vapors of the strong acid HCl(aq) andthe weak base NH3(aq) combine toform the acidic white salt ammoniumchloride (NH4Cl).
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A buffer is a solution that resists changes inpH when moderate amounts of acids or
bases are added.
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Buffer solutions are prepared by mixing a weak acid with its conjugate base
ora weak base with its conjugate acid
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Buffer solutions are prepared by mixing a weak acid with its conjugate base
ora weak base with its conjugate acid
Buffers can neutralize both OH– and H+
when one of these ions is added to thebuffered solution.
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A buffer solution can be prepared byusing the weak base ammonia, NH3, and
an ammonium salt, such as NH4Cl.
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A buffer solution can be prepared byusing the weak base ammonia, NH3, and
an ammonium salt, such as NH4Cl.
• When acid is added, NH3 reacts with H+.NH3 + H+ NH4
+
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A buffer solution can be prepared byusing the weak base ammonia, NH3, and
an ammonium salt, such as NH4Cl.
• When acid is added, NH3 reacts with H+.NH3 + H+ NH4
+
• If a base is added, the NH4+ ion from the
salt reacts with the OH–.NH4
+ + OH- NH3 + H2O
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Another buffer system contains the weakacid acetic acid, HC2H3O2, and the salt
sodium acetate, NaC2H3O2.
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Another buffer system contains the weakacid acetic acid, HC2H3O2, and the salt
sodium acetate, NaC2H3O2.
• If base is added, the weak acid reacts toneutralize the addition.HC2H3O2 + OH- C2H3O2
- + H2O
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Another buffer system contains the weakacid acetic acid, HC2H3O2, and the salt
sodium acetate, NaC2H3O2.
• If base is added, the weak acid reacts toneutralize the addition.HC2H3O2 + OH- C2H3O2
- + H2O
• If acid is added, the acetate ion from theNaC2H3O2 will neutralize the added H+.C2H3O2
- + H+ HC2H3O2
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The buffer capacity is theamount of acid or base thatcan be added to a buffersolution before a significantchange in pH occurs.