S03 Properties of Acids and Bases
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42 Terms
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is an electrolyte?
A charged molecule.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What defines a strong electrolyte?
It is completely charged when dissolved in water
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What defines a weak electrolyte?
Its charged and uncharged forms exist in equilibrium in solution.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is a Brønsted-Lowry acid?
A proton H+ donor.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is a Brønsted-Lowry base?
A proton H+ acceptor.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
How does acid or base strength affect dissociation in solution?
How does acid or base strength affect dissociation in solution?
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
How do strong acids dissociate in solution?
They dissociate completely.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
How do weak acids dissociate in solution?
They dissociate partially.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
How do strong bases dissociate in solution?
They dissociate completely.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
How do weak bases dissociate in solution?
They dissociate partially.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What arrow type in a chemical equation indicates complete ionization?
A single arrow.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What arrow type in a chemical equation indicates partial ionization?
An equilibrium arrow.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is the acid dissociation constant Ka?
A quantitative measure of the strength of an acid.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is the relationship between acid strength and Ka?
The stronger the acid, the higher the Ka value.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is the formula for pKa?
-log Ka
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is the base dissociation constant Kb?
A quantitative measure of the strength of a base
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is the relationship between base strength and Kb?
The stronger the base, the higher the Kb value.
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is the formula for pKb?
pKb = -log Kb
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is Kw?
The ionization constant of water under pure conditions, equal to 1.0×10-14
Learning Objective 1: Define electrolytes, acids, and bases, and describe the effect of acid/base strength on the overall dissociation of those molecules
What is the mathematical relationship between pKw , pKa , pKb?
pKw = pKa + pKb = 14
Learning Objective 2: Define pH and explain the relationship between the pH of the environment and the pKa value using the Henderson-Hasselbalch equation
What is pH?
The negative logarithm of the hydronium ion concentration ( -log[H3O+] )
Learning Objective 2: Define pH and explain the relationship between the pH of the environment and the pKa value using the Henderson-Hasselbalch equation
What is the Henderson-Hasselbalch equation?
pH = pKa + log ( [A-]/[HA] )
Learning Objective 2: Define pH and explain the relationship between the pH of the environment and the pKa value using the Henderson-Hasselbalch equation
In the Henderson-Hasselbalch equation, what does $[A^-]$ represent?
The conjugate base
Learning Objective 2: Define pH and explain the relationship between the pH of the environment and the pKa value using the Henderson-Hasselbalch equation
In the Henderson-Hasselbalch equation, what does [HA] represent?
The conjugate acid.
Learning Objective 2: Define pH and explain the relationship between the pH of the environment and the pKa value using the Henderson-Hasselbalch equation
What is the ratio of conjugate base to conjugate acid when pH = pKa
1 : 1
Learning Objective 2: Define pH and explain the relationship between the pH of the environment and the pKa value using the Henderson-Hasselbalch equation
What happens to solution pH when an acid is added to unbuffered water?
t decreases significantly due to an increase in H+ concentration.
Learning Objective 2: Define pH and explain the relationship between the pH of the environment and the pKa value using the Henderson-Hasselbalch equation
What happens to solution pH when a base is added to unbuffered water?
It increases significantly due to an increase in OH- concentration.
Learning Objective 3: Explain how buffers work to maintain relatively constant pH and describe how acid/base titration curves can be used to illustrate the buffering range
What is a buffer?
A combination of substances in aqueous solution that resists changes in pH when small amounts of acids or bases are added.
Learning Objective 3: Explain how buffers work to maintain relatively constant pH and describe how acid/base titration curves can be used to illustrate the buffering range
What are the two components of an acidic buffer system?
A weak acid and the salt containing its conjugate base.
Learning Objective 3: Explain how buffers work to maintain relatively constant pH and describe how acid/base titration curves can be used to illustrate the buffering range
What are the two components of a basic buffer system?
A weak base and the salt containing its conjugate acid.
Learning Objective 3: Explain how buffers work to maintain relatively constant pH and describe how acid/base titration curves can be used to illustrate the buffering range
How does a buffer system neutralize added base?
The weak acid component reacts with and neutralizes the added base.
Learning Objective 3: Explain how buffers work to maintain relatively constant pH and describe how acid/base titration curves can be used to illustrate the buffering range
How does a buffer system neutralize added acid?
How does a buffer system neutralize added acid?
Learning Objective 3: Explain how buffers work to maintain relatively constant pH and describe how acid/base titration curves can be used to illustrate the buffering range
What rule of thumb determines the effective buffering range of a buffer?
pKa ± 1pH unit
Learning Objective 3: Explain how buffers work to maintain relatively constant pH and describe how acid/base titration curves can be used to illustrate the buffering range
On a titration curve, what point corresponds to the midpoint of the buffering region where pH = pKa?
The point where 0.5 equivalents of base have been added
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
What is the primary biological buffer system in blood plasma?
The carbonic acid/bicarbonate buffer system H2CO3 / HCO3-
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
What enzyme catalyzes the conversion of CO2 and water to H2CO3? Carbonic anhydrase. What is the pKa of the carbonic acid/bicarbonate buffer system in blood?
6.3
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
What system primarily maintains intracellular pH?
Inorganic phosphate H2PO-4 / HPO-42 and proteins.
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
What is the pKa of the intracellular inorganic phosphate buffer system?
7.2
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
How do kidney cells regulate urinary pH using ammonia NH3?
They generate and excrete NH3 in urine as NH4+ in proportion to blood proton concentration.
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
What is the pKa of the NH3 / NH4+ system?
9.25
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
Why must blood concentrations of ammonia NH3 be kept very low?
Ammonia is toxic to neural tissues.
Learning Objective 4: Describe the biological buffer systems that maintain pH intracellularly and extracellularly
How is stomach HCl neutralized when contents enter the small intestine?
It is neutralized by bicarbonate to prevent degradation of digestive enzymes