Acids And Bases - Lecture 15 Flashcards
What is an Arrhenius acid?
Substances that contain hydrogen and dissociates in water to form a hydrogen ion
What is an Arrhenius base?
Substances that contain the hydroxyl group (OH) and dissociates in water to form a hydroxide ion and a cation
What does an Acid produce according to the theory of Arrhenius in water
H+ ion (proton)
What does a base produce according to the theory of Arrhenius in Water?
OH- ion (hydroxide ion)
What is a strong acid according to Arrhenius?
Completely dissociates/fully ionised in solution and produces a lot of Hydrogen ions (H+)
What is a weak acid according to Arrhenius?
Is one that is only partially ionised/slightly dissociates in water and produces only a few H+ Ions (hydrogen ions)
Examples of strong acids according to Arrhenius?
Hydrochloric acid , Sulphuric acid, hydrobromic acid, hydroiodic (hydriodic) acid, nitric acid and perchloric acid
Examples of weak acids according to Arrhenius
Hydrofluoric acid, hydrosulfuric acid, hydrocyanic acid, acetic acid (ethanoic acid)
Monoprotic Acids
Acids that produce only one proton (H+) when dissolved in water
Polyprotic Acids
Acids that produce more than one H+ ion in water
Strong base according to Arrhenius
Strong electrolyte, which is completely ionised/completely dissociates in water (aqueous solution) to produce hydroxide ions (OH-)
Weak base according to Arrhenius
Only partially ionise/slightly dissociate in water to produce OH- ions (hydroxide ions)
Acid + Base =
Salt + Water
Base that dissolves in Water is called an
Alkali
Acid + Metal =
Salt + Hydrogen
Acids + Metal Carbonate =
Salt + Water and CO2 gas given off
Acids and Bases are
Electrolytes
Neutralisation
Reaction between an acid and a base to form a salt and water
Why does Neutralisation Occur?
Hydrogen ions (H+) and hydroxide ions (OH-) react to produce water
State 3 limitations of the Arrhenius theory of acids and bases
- Limited to acid-base reactions that place in water
- Restricts acids to hydrogen containing species and bases to hydroxide containing species
- Does not explain how certain substances can be amphoteric
Amphoteric
Substance that can act as both an acid and a base
Bronsted Lowry acid
Proton donor (H+)
Bronsted Lowry Base
Proton (H+) acceptor (must contain lone pair of electrons)
Conjugate pair
A pair of substances, an acid and a base, that differ by one H+
Conjugate Acid
Base + Hydrogen ion (H+)
Conjugate Base
Acid - Hydrogen ion (H+)
According to BL theory, acids may be
Cations, neutral molecules or anions
According to BL theory, bases may be
Anions or neutral molecules
Is water an amphoteric substance
Yes
Protophilic solvents
Act as proton acceptors (bases)
Protogenic solvent
Proton donors (acids)
Amphiprotic Solvents
Act as an acid or base (water, alcohol)
Aprotic Solvents
Solvents which will neither donate nor accept protons
Eg.// benzene, carbon tetrachloride
Lewis Acid
Electron pair acceptor
Lewis Base
Electron pair donor
Acid according to Lewis
Substance that can accept a pair of electrons from another atom to form a new bond
Base according to Lewis
Substances that can donate an electron pair to another atom to form a new bond
Lewis definition includes
Metal ions and other electron pairs as acids
Lewis acid …..
Has an empty atomic orbital of low energy that can accommodate a pair of electrons
The process of neutralisation of a Lewis Base forms
Coordinate Covalent bond between an acid and base
The product of Lewis Acid-Base reaction is referred to as
Adduct
Example of Lewis acid-base adducts
Complex ions
Advantages of Lewis Theory
- Expands acid base reactions to include ,any substances without H in the formula
- Used to explain the effect of compounds which act as an acid in nonaqueous organic solvents
Limitation of Lewis Theory
- Includes all the coordination reactions and coordination compounds which may not always be true
- Cannot explain the behaviour of well known protonic acids which do not form coordination bonds with bases
- Relative strengths of acids and bases cannot be explained by this theory
