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Questions and Answers
What is the pH of a neutral aqueous solution at 25°C?
What is the pH of a neutral aqueous solution at 25°C?
- 7 (correct)
- 8
- 6
- 9
How does the addition of a weak acid affect the pH of a solution?
How does the addition of a weak acid affect the pH of a solution?
- It decreases H+ concentration and lowers pH.
- It increases H+ concentration and raises pH.
- It has no effect on H+ concentration or pH.
- It increases H+ concentration and lowers pH. (correct)
What happens to the hydroxide ion concentration in a solution when a base is added?
What happens to the hydroxide ion concentration in a solution when a base is added?
- It increases, leading to higher H+ concentration.
- It decreases, leading to lower H+ concentration. (correct)
- It decreases and raises the overall pH.
- It remains constant regardless of H+ concentration.
What is the relationship between pH and hydrogen ion concentration?
What is the relationship between pH and hydrogen ion concentration?
Which of the following describes a solution with a pH of 3?
Which of the following describes a solution with a pH of 3?
What is the pH range of most biological fluids such as blood and saliva?
What is the pH range of most biological fluids such as blood and saliva?
What chemical system in the blood helps maintain a stable pH?
What chemical system in the blood helps maintain a stable pH?
At what pH value does human blood become dangerously acidic?
At what pH value does human blood become dangerously acidic?
What happens when acids dissolve in water?
What happens when acids dissolve in water?
Which of the following defines a base?
Which of the following defines a base?
What is the role of sodium hydroxide (NaOH) in water?
What is the role of sodium hydroxide (NaOH) in water?
What characterizes a solution with a pH of 7?
What characterizes a solution with a pH of 7?
Which statement is true about ammonia (NH3)?
Which statement is true about ammonia (NH3)?
What effect does adding hydrochloric acid (HCl) have on a solution?
What effect does adding hydrochloric acid (HCl) have on a solution?
Which of the following ions is formed when a water molecule loses a proton?
Which of the following ions is formed when a water molecule loses a proton?
What is the pH characteristic of a strong acid solution compared to pure water?
What is the pH characteristic of a strong acid solution compared to pure water?
What is the primary function of a buffer in a biological fluid?
What is the primary function of a buffer in a biological fluid?
What is the effect of adding a strong acid to a liter of blood compared to pure water?
What is the effect of adding a strong acid to a liter of blood compared to pure water?
What compound forms when carbon dioxide reacts with water in blood plasma?
What compound forms when carbon dioxide reacts with water in blood plasma?
What is the reaction direction of the carbonic acid-bicarbonate system when the H+ concentration in blood rises?
What is the reaction direction of the carbonic acid-bicarbonate system when the H+ concentration in blood rises?
How does ocean acidification occur in relation to human activities?
How does ocean acidification occur in relation to human activities?
What role does bicarbonate ion (HCO3-) play in the carbonic acid-bicarbonate buffering system?
What role does bicarbonate ion (HCO3-) play in the carbonic acid-bicarbonate buffering system?
What happens to the concentration of H+ ions when carbonic acid dissociates in blood?
What happens to the concentration of H+ ions when carbonic acid dissociates in blood?
Which of the following best describes the components of a buffer solution?
Which of the following best describes the components of a buffer solution?
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Study Notes
Hydrogen Ions and Hydroxide Ions
- Hydrogen ion (H+) is a proton with a charge of 1+; a hydroxide ion (OH-) is a byproduct of water losing a proton.
- Hydronium ion (H3O+) forms when a proton binds with a water molecule.
- H+ and OH- concentrations significantly impact cell proteins and complex molecules.
Acids and Bases
- Acids increase hydrogen ion concentration in a solution (e.g., hydrochloric acid, HCl, donates H+ in water).
- Bases decrease hydrogen ion concentration, either by accepting H+ (e.g., ammonia, NH3) or dissociating to produce hydroxide ions (e.g., sodium hydroxide, NaOH).
- Solutions with higher OH- concentration than H+ are termed basic; neutral solutions have equal concentrations.
pH Scale
- The pH scale quantifies acidity/basicity; a pH of 7 indicates neutrality, while values below 7 are acidic and above 7 are basic.
- The product of H+ and OH- concentrations in any aqueous solution at 25°C is constant at 10^-14.
- Each pH unit change represents a tenfold change in H+ and OH- concentrations.
- A pH of 3 is 1,000 times more acidic than a pH of 6.
Biological Implications
- Most biological fluids are within the pH range of 6–8. Human blood maintains a pH around 7.4, crucial for survival.
- Small pH changes can be harmful since cellular reactions are sensitive to H+ and OH- levels.
- Strong acid addition to pure water drastically lowers pH but has minimal impact on blood pH due to buffers.
Buffers
- Buffers stabilize pH in biological fluids by neutralizing excess H+ or OH-.
- Buffer solutions typically contain a weak acid and its corresponding base, capable of reversible reactions with hydrogen ions.
- An example of a buffering system is carbonic acid (H2CO3) and bicarbonate ion (HCO3-), regulating blood pH by shifting equilibrium as needed.
Ocean Acidification
- Human activities, particularly fossil fuel burning, increase atmospheric CO2, contributing to global warming.
- About 25% of carbon dioxide produced dissolves in oceans, forming carbonic acid that lowers ocean pH, known as ocean acidification.
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