Here we will consider some reactions of a weak acid (HA) and a weak base (in this case, the conjugate of A). Recall that in water acids and bases undergo the following reactions: HA+ H20 H30 + A AH20 OH HA and Write expressions for K, and Kb 1) 2) Write a balanced equation for the reaction of a weak acid (HA) with a strong base, OH- (From, for example NaOH, which dissociates completely to OH in solution). Write an expression for Keq. Do you expect Keg to be small or large for this reaction? 3) Write a balanced equation for the reaction of a weak base (A) with a strong acid, H+, (From, for example, HCl which dissociates completely to Ht in solution). Write a balanced equation for this reaction. Do you expect Keg to be small or large for this reaction? 4) How do your Keg for each reaction compare to your expressions for Ka and Kb? AASonic We have a buffer when we have a mixture of HA and A. Consider a buffer with equal amounts of Acetic Acid (pKa 4.76) and Acetate (For example, 25.0 mls of 0.100 M HAc and 25.0 mls of 0.100 M Ac-). What is the pH of this buffer? Let's calculate the pH change upon addition of 5.00 mls of 0.100 M HCl. Uslng our reaction from part 3, fill in the initial moles of each species, then use stoichiometry to calculate change and final. 5) НА H + A> Initial Change Final Calculate the pH An alternate way to make a buffer is to mix a strong base with a weak acid. Let's look at how 6) this works. Consider a solution of 25.0 mls of 0.200 M Acetic Acid. Add to it 25.0 mLs of 0.100 M NaOH. Using our reaction from part 2, fill in initial moles of each species. Use stoichiometry to calculate change/final. Compare the final moles and concentrations to the initial buffer in part 5 A +H20 ОН + HA Initial Change Final
Here we will consider some reactions of a weak acid (HA) and a weak base (in this case, the conjugate of A). Recall that in water acids and bases undergo the following reactions: HA+ H20 H30 + A AH20 OH HA and Write expressions for K, and Kb 1) 2) Write a balanced equation for the reaction of a weak acid (HA) with a strong base, OH- (From, for example NaOH, which dissociates completely to OH in solution). Write an expression for Keq. Do you expect Keg to be small or large for this reaction? 3) Write a balanced equation for the reaction of a weak base (A) with a strong acid, H+, (From, for example, HCl which dissociates completely to Ht in solution). Write a balanced equation for this reaction. Do you expect Keg to be small or large for this reaction? 4) How do your Keg for each reaction compare to your expressions for Ka and Kb? AASonic We have a buffer when we have a mixture of HA and A. Consider a buffer with equal amounts of Acetic Acid (pKa 4.76) and Acetate (For example, 25.0 mls of 0.100 M HAc and 25.0 mls of 0.100 M Ac-). What is the pH of this buffer? Let's calculate the pH change upon addition of 5.00 mls of 0.100 M HCl. Uslng our reaction from part 3, fill in the initial moles of each species, then use stoichiometry to calculate change and final. 5) НА H + A> Initial Change Final Calculate the pH An alternate way to make a buffer is to mix a strong base with a weak acid. Let's look at how 6) this works. Consider a solution of 25.0 mls of 0.200 M Acetic Acid. Add to it 25.0 mLs of 0.100 M NaOH. Using our reaction from part 2, fill in initial moles of each species. Use stoichiometry to calculate change/final. Compare the final moles and concentrations to the initial buffer in part 5 A +H20 ОН + HA Initial Change Final
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Chapter16: Acid-base Equilibria
Section: Chapter Questions
Problem 16.157QP: Weak base B has a pKb of 6.78 and weak acid HA has a pKa of 5.12. a Which is the stronger base, B or...
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Question
5) and 6)
Transcribed Image Text:Here we will consider some reactions of a weak acid (HA) and a weak base (in this case, the conjugate
of A). Recall that in water acids and bases undergo the following reactions:
HA+ H20 H30 + A
AH20 OH HA
and
Write expressions for K, and Kb
1)
2) Write a balanced equation for the reaction of a weak acid (HA) with a strong base, OH-
(From, for example NaOH, which dissociates completely to OH in solution). Write an
expression for Keq. Do you expect Keg to be small or large for this reaction?
3) Write a balanced equation for the reaction of a weak base (A) with a strong acid, H+, (From,
for example, HCl which dissociates completely to Ht in solution). Write a balanced equation for
this reaction. Do you expect Keg to be small or large for this reaction?
4)
How do your Keg for each reaction compare to your expressions for Ka and Kb?
Transcribed Image Text:AASonic
We have a buffer when we have a mixture of HA and A. Consider a buffer with equal amounts
of Acetic Acid (pKa 4.76) and Acetate (For example, 25.0 mls of 0.100 M HAc and 25.0 mls of
0.100 M Ac-). What is the pH of this buffer?
Let's calculate the pH change upon addition of 5.00 mls of 0.100 M HCl. Uslng our reaction
from part 3, fill in the initial moles of each species, then use stoichiometry to calculate change
and final.
5)
НА
H +
A>
Initial
Change
Final
Calculate the pH
An alternate way to make a buffer is to mix a strong base with a weak acid. Let's look at how
6)
this works. Consider a solution of 25.0 mls of 0.200 M Acetic Acid. Add to it 25.0 mLs of 0.100
M NaOH. Using our reaction from part 2, fill in initial moles of each species. Use stoichiometry
to calculate change/final. Compare the final moles and concentrations to the initial buffer in
part 5
A +H20
ОН +
HA
Initial
Change
Final
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