Acids, Bases & Buffers Quiz

Questions and Answers

What exists in a system of at least 2 states when the populations of the two states are constant?

Equilibrium

What does Le Châtelier's Principle state?

Systems will always strive to create new substances.

Systems will always strive to reestablish the state of equilibrium. (correct)

Equilibrium is only achieved by adding reactants.

Changing pressure has no effect on equilibrium.

What is the equilibrium constant (K)?

A numerical description of the balance of reactants and products in molar concentrations.

What does an acid do according to the Bronsted definition?

Donates hydrogen ion to a base. Signup and view all the answers

A conjugate base can only accept a hydrogen ion if it contains a hydroxide anion.

False Signup and view all the answers

Which of the following describes an amphiprotic species?

A species that can act as either an acid or a base. Signup and view all the answers

What type of solution is a pH buffer?

A solution that resists changes in pH. Signup and view all the answers

What happens when a strong acid is added to a buffered solution?

The weak base in the buffer reacts with the acid to give a weak acid. Signup and view all the answers

How do weak acids behave in water?

They establish a dynamic equilibrium. Signup and view all the answers

Study Notes

Chemical Equilibria

Equilibrium occurs when populations of at least two states remain constant in a system.
Chemical reactions are typically reversible, allowing reactants to form products and vice versa.
The use of double arrows indicates a reversible and equilibrating process.

Le Châtelier’s Principle

Systems attempt to restore equilibrium when disturbed.
Adding reactants shifts equilibrium toward products; adding products shifts it toward reactants.
In the alveoli, high oxygen tension promotes oxygen binding to hemoglobin, while low tissue concentration facilitates release.
Changes in volume and pressure also affect equilibrium; increasing FiO2 increases dissolved oxygen levels.

Equilibrium Constant

The equilibrium constant (K) quantifies the ratio of reactant and product concentrations at equilibrium.
For a reaction aA + bB ⇌ cC + dD, K is expressed as K = [D]d[C]c / [A]a[B]b.
Specific constants, like Ka, indicate the equilibrium of weak acid ionization.
A K value greater than 1 indicates a product-favored reaction.

Acids and Bases

Acids increase H+ concentration; in water, H+ exists as hydronium ions (H3O+).
Bases raise hydroxide ion (OH-) levels in aqueous solutions.
According to the Brønsted definition, acids donate H+ to bases which accept it.
In the reaction HCl → H+ + Cl-, H+ is the acid and Cl- is a conjugate base that can accept H+.
Amphiprotic species, like bicarbonate (HCO3-), can act as acids or bases, exemplifying polyprotic acids that can release multiple H+ ions.
Weak acids establish a dynamic equilibrium when dissolved in water; their strength is indicated by Ka, reflecting the degree of H+ donation.
Example: For carbonic acid (H2CO3), Ka = 7.94x10^-7, and pKa is calculated using pKa = -log(Ka), resulting in pKa of 6.1.

Buffers

pH buffers resist changes in pH by containing a weak acid (HA) and its conjugate base (A-).
When strong acids are introduced to a buffered solution, the weak base (A-) neutralizes it to form the weak acid (HA).
In the presence of strong bases, the weak acid (HA) reacts to produce water and the weak base (A-), maintaining pH stability.

Description

Test your knowledge on the concepts of acids, bases, and buffers in chemistry. This quiz covers the principles of chemical equilibria, including reversible reactions and the behavior of reactants and products. Enhance your understanding of these foundational topics in chemistry.