ACIDS, BASES, pH, pOH & BUFFERS Flashcards
How are acids and bases defined by: Arrhenius
Acids produce protons (H+) Bases produce (OH-)
This definition is relevant for water only
The solvent has no role to play in Arrhenius’ theory.
The nature of the solvent plays a critical role in acid-base properties of substances
How are acids and bases defined by: Bronsted-Lowry
Acids donate H+ ions
Bases accept H+ ions
Relevant for any solvent
What is a conjugate base and acid?
Conjugate base: the species formed when an acid donates a proton to another molecule or ion
Conjugate acid: the substance formed when a base accepts a proton
Stronger acids from weaker conjugate bases and vice versa
How are acids and bases defined by: Lewis
An acid is a substance that accepts electron pairs
A base is a substance that donates electron pairs
Describe a strong and weak acid
Strong acids: dissociates almost entirely into H3O+ ions in water
Weak acids: only a small percentage of molecules dissociate into ions in water
Describe a strong and weak base
Strong bases: Dissociates almost entirely into OH- ions in water
Weak bases: only a small percentage of molecules dissociate into ions in water
What are the pH limits of acids and bases?
Acids have a pH of less than 7
Bases have a pH of more than 7
What is a neutralisation reaction?
Acid-base reaction where an acid reacts with a base to produce a salt and water
When a solution is neutralised, it means that salts are formed form equal amounts of acids and bases
What is pH?
Whenever we talk about pH, we are referring to the concentration of H3O+ (hydronium) ions
What is pOH?
In the same way that pH is useful to describe the concentration of H3O+, pOH is a convenient way to express the concentration of OH
How do you find the weaker acids and weaker bases in a chemical equation?
- Identify the 2 acids in the equilibrium – one will be on the left and one on the right.
- Determine which is the stronger acid
- Identify the 2 bases and their relative strengths
- The equilibrium lied on the side of the weaker acid and the weaker base
What is volumetric analysis?
If we have a solution of a known concentration, we can add this to a solution of unknown concentration. If we have the volume of both used, we can determine the concentration of the unknown using our mole relationships
This technique is called volumetric analysis and the most common procedure or method to conduct volumetric analysis is via titration
What is the equivalence point?
The equivalence point in a titration is the point at which one reactant has been consumed exactly by the addition of the other reactant (i.e., when the amount of OH- = the amount of H+ in the solution)
The equivalence point is mid-way along the vertical section of each graph
What is the end point?
The end point is the point at which the indicator changes colour
What is a buffer solution?
A buffer solution is a solution with the ability to resist pH changes when small amounts of acid or base are added to it
The most common buffers include those consisting of equal amounts of a weak acid and a salt of its conjugate base
The amount of hydronium or hydroxide ions a buffer can absorb while resisting a change in pH is referred to as the buffer capacity
