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Questions and Answers
Which of the following best describes the behavior of a strong acid in an aqueous solution?
Which of the following best describes the behavior of a strong acid in an aqueous solution?
- It forms a weak base.
- It completely dissociates into ions. (correct)
- It partially dissociates into ions.
- It does not dissociate into ions.
Which of these acids is considered a weak acid?
Which of these acids is considered a weak acid?
- Sulfuric acid (H2SO4).
- Hydrochloric acid (HCl).
- Phosphoric acid (H3PO4). (correct)
- Nitric acid (HNO3).
What differentiates a monoprotic acid from a diprotic acid?
What differentiates a monoprotic acid from a diprotic acid?
- Their degree of dissociation in solution.
- The strength of conjugate base.
- The number of hydrogen ions produced per molecule. (correct)
- The pH of their solutions.
Which of the following is a characteristic property of bases?
Which of the following is a characteristic property of bases?
What is the primary function of a buffer solution?
What is the primary function of a buffer solution?
What is the primary ion released when a base dissolves in an aqueous solution?
What is the primary ion released when a base dissolves in an aqueous solution?
How does the strength of an acid related to its tendency to ionize?
How does the strength of an acid related to its tendency to ionize?
Which of the following is NOT a critical component of a buffer solution?
Which of the following is NOT a critical component of a buffer solution?
What is the purpose of a buffer solution?
What is the purpose of a buffer solution?
What is the ideal pH range for a buffer to function, where pKa of the weak acid is the reference?
What is the ideal pH range for a buffer to function, where pKa of the weak acid is the reference?
What happens when hydrogen ions are added to a buffer solution?
What happens when hydrogen ions are added to a buffer solution?
Which of the following describes the equilibrium constant (Ka) for acid ionization?
Which of the following describes the equilibrium constant (Ka) for acid ionization?
Which of the following is a weak base commonly used in antacids?
Which of the following is a weak base commonly used in antacids?
Which of the following is an example of a buffer system?
Which of the following is an example of a buffer system?
Which term refers to acids that have more than one ionizable proton per molecule?
Which term refers to acids that have more than one ionizable proton per molecule?
Why are buffers important in biological systems?
Why are buffers important in biological systems?
If a weak acid has a pKa of 6.2, what is the effective buffering range?
If a weak acid has a pKa of 6.2, what is the effective buffering range?
Which of these options is a buffer found in physiological systems mentioned in the text?
Which of these options is a buffer found in physiological systems mentioned in the text?
Which of these best describes how to prepare a buffer solution?
Which of these best describes how to prepare a buffer solution?
What is the term for a reaction where a biomolecule is split using water?
What is the term for a reaction where a biomolecule is split using water?
What type of reaction forms a biomolecule using two components, with the elimination of water?
What type of reaction forms a biomolecule using two components, with the elimination of water?
When water molecules ionize, what are the resulting ions?
When water molecules ionize, what are the resulting ions?
What is the term for a solution with an excess of hydrogen ions?
What is the term for a solution with an excess of hydrogen ions?
What does it mean when we say water is dipolar?
What does it mean when we say water is dipolar?
Why is water able to dissolve large quantities of charged compounds?
Why is water able to dissolve large quantities of charged compounds?
What kind of bonds enable water to dissolve many organic molecules with functional groups?
What kind of bonds enable water to dissolve many organic molecules with functional groups?
Within a water molecule, which atom is more electronegative?
Within a water molecule, which atom is more electronegative?
What does an acid release in solution?
What does an acid release in solution?
Flashcards
Acid
Acid
A compound that releases hydrogen ions (H+) when dissolved in water.
Acid Dissociation
Acid Dissociation
A compound that dissociates in aqueous solution to produce a proton (H+) and a conjugate base (A-).
Strong Acids
Strong Acids
Acids that ionize completely in solution.
Weak Acids
Weak Acids
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Monoprotic Acid
Monoprotic Acid
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Diprotic Acid
Diprotic Acid
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Polyprotic Acid
Polyprotic Acid
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Buffer
Buffer
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Base
Base
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Acid Dissociation Constant (Ka)
Acid Dissociation Constant (Ka)
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What is a buffer?
What is a buffer?
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What are the components of a buffer?
What are the components of a buffer?
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What is the buffer range?
What is the buffer range?
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What are essential factors when choosing a buffer?
What are essential factors when choosing a buffer?
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What is the phosphate buffer?
What is the phosphate buffer?
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What is the bicarbonate buffer?
What is the bicarbonate buffer?
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What is the protein buffer?
What is the protein buffer?
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How does a buffer regulate pH when an acid is added?
How does a buffer regulate pH when an acid is added?
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How does a buffer regulate pH when a base is added?
How does a buffer regulate pH when a base is added?
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What is the biological significance of buffers?
What is the biological significance of buffers?
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Hydrolysis
Hydrolysis
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Condensation Reaction
Condensation Reaction
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Water Ionization
Water Ionization
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Neutral Solution
Neutral Solution
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Proton Donor
Proton Donor
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Proton Acceptor
Proton Acceptor
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Acid Strength
Acid Strength
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Study Notes
Water
- Water is a direct participant in many biochemical reactions
- Hydrolysis reaction: A biomolecule is split apart by water
- Condensation reaction: A biomolecule is formed from two components with the elimination of water
- Water has a slight tendency to ionize into hydrogen (H+) and hydroxide (OH-) ions
- H₂O ⇌ H⁺ + OH⁻
- Free protons (H⁺) do not exist in solution; they immediately combine with water to form hydronium ions (H₃O⁺)
- Water can form acids and bases
Acids
- An acid is any ionic compound that releases hydrogen ions (H⁺) in solution
- Weak acids have a sour taste
- Strong acids are highly corrosive
- Examples:
- Ascorbic acid (Vitamin C)
- Citric acid (citrus fruits)
- Phosphoric acid (soft drinks, rust removal)
Types of Acids
- Strong acids dissociate completely in water
- Weak acids dissociate partially in water
- Monoprotic acids: release one ionizable proton (e.g., HCl)
- Diprotic acids: release two ionizable protons (e.g., H₂SO₄)
- Polyprotic acids: release more than two ionizable protons (e.g., H₃PO₄)
Bases
- A base is an ionic compound that releases hydroxide ions (OH⁻) in solution
- Bases are also called alkaline substances
- Taste: Bitter
- Touch: Slimy or soapy
- Reactivity: Strong bases are caustic on organic matter; react violently with acids
- Examples:
- Sodium hydroxide (lye, oven cleaners)
- Magnesium hydroxide (milk of magnesia, antacids, laxatives)
Dissociation Constants of Weak Acids and Bases
- Weak acids and bases do not completely ionize in water; the extent of ionization depends on pH
- Equilibrium constant (Ka) for a weak acid's ionization is called the acid dissociation constant
Buffers
- Definition: A solution that resists changes in pH when acid or base is added
- Components: A weak acid and its conjugate base (e.g., acetic acid and acetate, carbonic acid and bicarbonate)
Why Use Buffers?
- Enzyme reactions and cell functions have optimal pH ranges
- Maintain the structure and/or activity of biological materials
Factors in Choosing a Buffer
- The buffer should cover the desired pH range (generally ±1 pH unit from the pKa value of the weak acid)
- The buffer should not be toxic to the cells or organisms being studied
- The buffer should not interfere with the experiment
Buffers of Physiological Importance
- Phosphate buffer
- Bicarbonate buffer
- Protein buffer
How Buffers Regulate pH
- If hydrogen ions are added, the conjugate base reacts with them, forming the acid
- If hydroxide ions are added, the acid reacts with them, forming water and the conjugate base
Biological Importance of Buffer
- Body fluids (blood, cerebrospinal fluid, saliva) maintain a constant pH range
- Buffering is essential because hydrogen and hydroxyl ions are constantly produced by metabolism
Preparation of Buffer
- Buffers resist pH changes if the pH is near the pKa value of the weak acid
- Buffer range: ±1 pH unit from the pKa value
The Henderson-Hasselbalch Equation
- Describes the shape of titration curves for weak acids
- pH = pKa + log([conjugate base]/[acid])
Worked Example
- Calculating pH of a mixture of NaH₂PO₄ and Na₂HPO₄
- Calculating pH change when NaOH is added to a buffer solution
Additional Notes
- This study guide covers the slides provided in the image.
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Description
Explore the fundamental concepts of water and acids through this engaging quiz. Learn about the biochemical roles of water, hydrolysis, condensation reactions, and the classification of different types of acids. Test your knowledge on how acids function in various solutions and their characteristics!