Exam 3 Flashcards
(28 cards)
Identify a strong acid and explain why it is classified as strong.
A strong acid, such as HCl, fully ionizes in solution, meaning all of its molecules
dissociate to form H₃O⁺. This makes it a strong electrolyte.
Describe the key characteristics of a weak acid and how it behaves in solution.
A weak acid only partially ionizes in solution, meaning that at equilibrium, a mixture of
ionized and non-ionized molecules remain. Examples include HF and CH₃COOH.
Explain what makes a base strong and how it interacts with water.
A strong base, such as NaOH, fully dissociates in water to produce OH⁻ ions. This
complete dissociation makes it a strong electrolyte.
Define what it means for water to be amphoteric. Write the equation for the auto-ionization
of water.
Water is amphoteric because it can act as both an acid (donating H⁺) and a base
(accepting H⁺). An example is the auto-ionization reaction: H₂O + H₂O ⇌ H₃O⁺ + OH⁻.
What is the value of Kw at 25°C, and why is it important in acid-base chemistry?
Kw = 1.00 × 10⁻¹⁴ at 25°C. It is the ion-product constant for water, which defines the
relationship between H₃O⁺ and OH⁻ concentrations in aqueous solutions.
Kw = [H3O+][OH-]
Write the formula for calculating pH.
The pH formula is pH = -log[H₃O⁺]. This allows us to determine the acidity of a solution
based on its hydronium ion concentration.
If a solution has a pH of 5, classify it as acidic, basic, or neutral and justify your answer.
A solution with a pH of 5 is acidic because its pH is below 7, which is the neutral point
on the pH scale.
How does the value of Ka indicate if an acid is weak or strong?
If the value of Ka is smaller than that means it has a weak ionization, meaning a weak acid.
According to the Arrhenius definition, a base:
Produces OH- ions in a solution
How does the Bronsted-Lowry define a base?
A substance that accepts H+ ions.
Strong Acids
HCL, HBr, HI, HClO3, HClO4, HNO3, H2SO4
Define a neutral base
If substance is a conjugate base of a strong acid, it is NOT a base. Must be neutral in water!
Define a weak base
Every other anion, not a strong base or neutral
Ex. CO3- is a weak base
Define a weak acid
Cations of small, highly charged metals are weakly acidic.
EXCEPTION: Group 1 and 2 metals are NOT acidic!
What is a polyprotic acid?
An acid with multiple acidic hydrogens and each hydrogen has a Ka.
EX: H3PO4 has 3 hydrogens it can give away when exposed to H20, has 3 Ka values.
Strength of Ka values?
Ka1»_space; Ka2»_space; Ka3
Only use Ka1 in calculations
Remember!
In water, metals and nonmetals separate! Nonmetals and nonmetals stay together.
EXCEPTION: Halogens will always break apart
What is a Binary Acid?
A chemical formula containing H + any other element
EX: H2O or HCl
In what direction do binary acids get stronger?
Down the periodic table and to the right in the periodic table does the strength increase
What is an Oxyacid?
A chemical formula containing H-O-Y (Y being any other element)
What direction do Oxyacid’s get strong?
Up and to the right in the periodic table
Remember!
The more oxygens an acid has the stronger it is
EX: ClO3 is stronger than ClO2
What does it mean for the pH if the acid and base concentration are the same?
pH=pKa
What is the general rule for Ka of a weak acid?
Ka «_space;1
