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Questions and Answers
What percentage of the earth's surface is covered by water?
What percentage of the earth's surface is covered by water?
Which of the following is a property of water that contributes to its role as a solvent?
Which of the following is a property of water that contributes to its role as a solvent?
What does the term 'hydrophilic' refer to?
What does the term 'hydrophilic' refer to?
What is the primary reason for water's high boiling and melting points?
What is the primary reason for water's high boiling and melting points?
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What does osmosis describe?
What does osmosis describe?
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What does the term 'isotonic' refer to in relation to blood?
What does the term 'isotonic' refer to in relation to blood?
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Which type of molecules are described as hydrophobic?
Which type of molecules are described as hydrophobic?
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How many hydrogen bonds can a single water molecule form?
How many hydrogen bonds can a single water molecule form?
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What does the ionization constant Ka measure?
What does the ionization constant Ka measure?
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Which of the following best describes a buffer?
Which of the following best describes a buffer?
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What components are typically found in a buffer solution?
What components are typically found in a buffer solution?
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Which buffer system is primarily responsible for maintaining blood pH?
Which buffer system is primarily responsible for maintaining blood pH?
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What happens to bicarbonate ions when free hydrogen ions are present?
What happens to bicarbonate ions when free hydrogen ions are present?
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Why is it important for blood pH to remain constant?
Why is it important for blood pH to remain constant?
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What type of substances can buffers help organisms manage?
What type of substances can buffers help organisms manage?
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How do weak acids contribute to pH stabilization in a buffer system?
How do weak acids contribute to pH stabilization in a buffer system?
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What characterizes a hypertonic solution?
What characterizes a hypertonic solution?
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What is the pH value range that indicates a basic solution?
What is the pH value range that indicates a basic solution?
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How is pH defined mathematically?
How is pH defined mathematically?
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What is a characteristic of strong acids?
What is a characteristic of strong acids?
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Which of the following describes a weak acid?
Which of the following describes a weak acid?
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What happens to the concentration of H+ in the presence of a base?
What happens to the concentration of H+ in the presence of a base?
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What is the primary characteristic of a strong base?
What is the primary characteristic of a strong base?
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At a pH of 1 to 2, what type of environment is present?
At a pH of 1 to 2, what type of environment is present?
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Study Notes
Water, pH and Buffers
- Water is essential for life, acting as the medium for life processes.
- It covers about 73% of the Earth's surface and all living things depend on it.
- The human body is comprised of over 70% water, a major component of bodily fluids like blood, urine, and saliva.
- Water plays a crucial role in chemical reactions, as these reactions occur in an aqueous environment.
- Water dissolves nutrients, facilitating their transport.
- Proteins, polysaccharides, nucleic acids, and membranes adopt specific shapes in response to water's properties.
- Water's chemical properties are linked to the function of biomolecules, cells, and entire organisms.
Water's Physical Properties
- Water is a polar molecule, formed when two hydrogen atoms covalently bond with one oxygen atom.
- This creates an uneven distribution of charge, with partial negative charges on oxygen and partial positive charges on hydrogen.
- Polar molecules are drawn to other polar molecules and to ions.
- Water's polarity enables it to dissolve many substances.
Water's Importance (Continued)
- Water's uneven charge distribution leads to the formation of hydrogen bonds.
- Hydrogen bonds exist between water molecules and between water and polar solutes.
- Four hydrogen bonds per water molecule create water's high boiling point, high melting point, and large surface tension.
Water as a Solvent
- Water is an excellent solvent due to its ability to dissolve a wide range of organic and inorganic molecules.
- Hydrophilic molecules (Greek for "water-loving") readily dissolve in water.
- Hydrophobic molecules (non-polar) do not dissolve in water, including lipids and waxes.
Osmosis
- Osmosis is the movement of water from a region of high water concentration to a region of low water concentration across a semi-permeable membrane.
- This is crucial in maintaining cellular balance.
Tonicity
- Isotonic solutions have the same osmotic pressure as blood.
- Hypotonic solutions have a lower osmotic pressure than blood.
- Hypertonic solutions have a higher osmotic pressure than blood.
Chemical Properties of Water (Continued)
- Water slightly ionizes into hydrogen ions (H+) and hydroxide ions (OH-).
- At 25°C, the concentrations of H+ and OH- are equal (1 x 10-7 M).
- The concentration of water is constant (55.5 M).
pH
- pH is a shorthand way to express the concentration of H+ ions in a solution.
- The pH scale is logarithmic, ranging from 0 to 14.
- A pH of 7 is neutral.
- pH values below 7 are acidic.
- pH values above 7 are basic (alkaline).
- pH is defined as the negative logarithm of the hydrogen ion concentration (pH = -log[H+]).
- pOH is the negative logarithm of the hydroxide ion concentration (pOH = -log[OH-]).
- pH + pOH = 14
pH Scale (Continued)
- The pH of a solution indicates its acidity or alkalinity
- Extremes in pH (far from 7) are generally inhospitable to life
- Human cells (pH ~ 6.8) and blood (pH ~ 7.4) are close to neutral.
Acids and Bases
- An acid is a substance that increases the concentration of H+ ions in a solution, typically by releasing hydrogen atoms.
- An acid is a proton donor (HA → H+ + A-).
- Strong acids completely ionize in water
- Weak acids do not completely ionize in water.
- A base provides either hydroxide ions (OH-) or other negatively-charged ions that react with H+ ions, reducing their concentration and raising the pH.
Strong and Weak Acids/Bases
- Strong acids and bases completely ionize in water
- Weak acids and bases only partially ionize in water
Ionization Constants (Ka)
- Ka is a measure of an acid's ability to dissociate.
- Strong acids have high Ka values.
- Weak acids have low Ka values
Physiological pH
- Maintaining a constant internal pH is crucial for human well-being.
- The pH inside cells is approximately 7.
- Human blood has a pH of 7.4 +/- 0.05.
- This is achieved by using buffers.
Buffers
- Buffers resist changes in pH, crucial for maintaining homeostasis.
- They are solutions of a weak acid and its conjugate base, or a weak base and its conjugate acid.
- Conjugate base: The negatively-charged part of an acid after losing a proton.
- Buffers resist pH changes by neutralizing acids or bases.
- They consist of an acidic compound and a basic compound.
Body Buffer Systems
- Protein buffers are the most significant buffer system in the body.
- Hemoglobin is a protein buffer.
- Phosphate is a major intracellular buffer.
- The carbonic acid-bicarbonate buffer system is crucial in blood.
- Carbonic acid (H2CO3) dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).
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Description
Test your understanding of the essential role of water in biological systems and its unique physical properties. This quiz covers topics such as the importance of water for life, its chemical behavior, and its impact on biomolecules. Dive into the fascinating world of aqueous environments and buffers.
