Acid-Base equilibria Flashcards
What is the pH scale?
A scale used to measure and determine if a solution is acidic, neutral or basic.
It stands for the potential of hydrogen, that is, the concentration of hydrogen ions in a solution
0-6.9 = acidic
7.0 = neutral
7.1 - 14 = basic or alkaline
(lower the acid the stronger it is and vice versa)
Describe the traditional / Arrhenius theory
Acids : its properties were due to the presence of hydrogen atoms
-defined as a compound that produced H+ ions in a aqueous solution
Base : its properties were due to the presence of OH- ions
-defined as a compound that produces OH- ions in aqueous solutions
This theory explained a lot of acid-base chemistry but was limited because it only described one type of base, those containing the OH- ion
Describe the Bronsted-Lowry Theory
Acid : proton donor
Base : proton acceptor
theory : sometimes the the H+ ion is not stable enough on its own so it reacts with water to form the hydronium ion
*look at picture for diagram
What is an Amphiprotic Substance?
A substance that can act as both a Bronsted - Lowry acid or base, depending on the reaction.
What is a conjugate acid / base?
Since acid-base reactions are reversible, a proton transfer may happen in the forward reaction and the reverse reaction.
- When the acid or base are on the product side it’s called the conjugate acid or base
-The pairs only differ by a hydrogen ion (a proton)
Describe the conjugate acid
It’s the substance that forms when a base accepts a proton
Describe the conjugate base
It’s the substance that forms when an acid loses a proton
Describe strong & weak acids and its H+ ions
Strong acids : produce many H+ ions
Weak acids : produce few H+ ions
The stronger the acid the more H+ ions are produced.
Describe strong & weak bases and its OH- ions
Strong base : produce many OH- ions
Weak base : produce few OH- ions
The stronger the base, the more OH- ions are produced
What kind of reactions are strong acid and bases?
They’re essentially one way reactions - the acid or base breaks down completely to produce ions.
What kind of reactions are weak acid and bases?
They do not ionize completely, which is represented by a double arrow.
For weak electrolytes, equilibrium lies to the left side of the equation (reactant).
What are ionization constants?
Since acid/base solutions are systems at equilibrium we can write equilibrium constant expressions for the systems
Acids : Ka
Base : Kb
Water : Kw
What do large Ka and Kb mean?
-A large Ka means there are many H+ ions in a solution, so a strong acid
-A large Kb means there are many OH- ions in a solution, so a strong base
Key points about Kw
The value is given
- As long as temperature remains constant Kw does not change
-The value is very small, meaning that very few ions are present. Most water remains “intact” as H2O, and few ions form
What is an acid-base titration?
A process used to determine the concentration of an acid solution or base solution. An acidic or basic solution of known concentration is used to neutralize a known volume of a basic or acid solution with an unknow concentration.
