Biology: Acids and Bases

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Questions and Answers

What is the pH of a neutral aqueous solution at 25°C?

7 (correct)

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?

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?

As pH increases, H+ concentration decreases. Signup and view all the answers

Which of the following describes a solution with a pH of 3?

It is more acidic than a solution with pH 6. Signup and view all the answers

What is the pH range of most biological fluids such as blood and saliva?

6 to 8 Signup and view all the answers

What chemical system in the blood helps maintain a stable pH?

Carbonic acid-bicarbonate buffer system Signup and view all the answers

At what pH value does human blood become dangerously acidic?

7.0 Signup and view all the answers

What happens when acids dissolve in water?

They donate hydrogen ions to the solution. Signup and view all the answers

Which of the following defines a base?

A substance that increases the hydroxide ion concentration of a solution. Signup and view all the answers

What is the role of sodium hydroxide (NaOH) in water?

It reduces H+ concentration by forming water. Signup and view all the answers

What characterizes a solution with a pH of 7?

It contains equal concentrations of hydrogen and hydroxide ions. Signup and view all the answers

Which statement is true about ammonia (NH3)?

It interacts reversibly with hydrogen ions to form ammonium. Signup and view all the answers

What effect does adding hydrochloric acid (HCl) have on a solution?

It increases hydrogen ion concentration, creating an acidic solution. Signup and view all the answers

Which of the following ions is formed when a water molecule loses a proton?

Hydroxide ion (OH-) Signup and view all the answers

What is the pH characteristic of a strong acid solution compared to pure water?

It has a higher concentration of H+ ions than OH- ions. Signup and view all the answers

What is the primary function of a buffer in a biological fluid?

To minimize changes in concentrations of H+ and OH- ions Signup and view all the answers

What is the effect of adding a strong acid to a liter of blood compared to pure water?

Blood experiences a smaller decrease in pH than water Signup and view all the answers

What compound forms when carbon dioxide reacts with water in blood plasma?

Carbonic acid Signup and view all the answers

What is the reaction direction of the carbonic acid-bicarbonate system when the H+ concentration in blood rises?

The reaction shifts to the left, forming more carbonic acid Signup and view all the answers

How does ocean acidification occur in relation to human activities?

By fossil fuel combustion releasing CO2, which then forms carbonic acid Signup and view all the answers

What role does bicarbonate ion (HCO3-) play in the carbonic acid-bicarbonate buffering system?

It removes hydrogen ions when pH drops Signup and view all the answers

What happens to the concentration of H+ ions when carbonic acid dissociates in blood?

The concentration of H+ ions increases Signup and view all the answers

Which of the following best describes the components of a buffer solution?

A weak acid and its corresponding weak base Signup and view all the answers

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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Description

Explore how acidic and basic conditions impact living organisms. This quiz covers essential concepts like hydrogen ions, hydroxide ions, and the pH scale, essential for understanding biological processes.