Chemistry: Chapter 12 - Acids and Bases

Arrhenius acid

a substance that dissociates in water to produce H+ ions (hydronium ions)

Arrhenius weak acid

does not readily dissociate in water to produce H+ ions

Arrhenius strong acid

one that readily dissociates in water to produce H+ ions

Arrhenius base

a substance that dissociates in water to produce OH- ions (hydroxide ions)

Arrhenius strong base

one that readily dissociates in water to produce OH- ions

Arrhenius weak base

one that does not readily dissociate in water to produce OH- ions

Limitations of Arrhenius

• It is H3O+ (hydronium) that exists in water, not H+ (H+ ions are protons and cannot exist independently)

• Restricted to aqueous solutions even though not all a-b reactions require water, preventing the use of other solvents, i.e. his theory is too restrictive by limiting himself to water

• doesn’t account for amphiprotic/amphoteric behaviour

• doesn’t account for bases without OH- (e.g. NH3)

• he based his definitions to reactions occuring in polar water, so non-polar organic solvents were excluded

Bronstead-Lowry theory

• an acid is a proton (H+) donor

• a base is a proton (H+) acceptor

B-L strong acid

readily donate protons - good proton donor

B-L weak acid

do not readily donate protons - poor proton donor

B-L strong base

readily accept protons - good proton acceptor

B-L weak base

does not readily accept protons - poor proton acceptor

conjugate acid-base pair

any pair consisting of an acid and base that differ by a proton → action is also reversible

acid →

changes into its conjugate base when it donates a proton

base →

changes into its conjugate acid when it accepts a proton

strong vs weak

• the stronger the acid/base, the weaker the conjugate base/acid

• the weaker the acid/base, the stronger the conjugate base/acid

amphiprotic/amphoteric substances

a substance that can act as both an acid and a base, e.g. water

neutralisation

when acids and bases react with each other, they cancel each other out to neutralise to form a salt and water

salt

the substance formed in neutralisation when the hydrogen in an acid is replaced by a metal (or ammonium ion)

neutralisation reaction…

it is formed when the H+ of the acid is replaced by a metal ion of NH4+

the non-metal part of a salt is called a radical or complex ion

alkali

a base that is soluble in water

monobasic acids

produces one H+ ion in a solution, e.g. HCl & HNO3

dibasic acids

produces two H+ ions in solution, e.g. H2SO4

tribasic acids

produces three H+ ions in solution, e.g. H3PO4

conjugate acid

a base plus a H+ ion

conjugate base

an acid minus a H+ ion

reactions of acids w/ metals and bases

1. ACID + METAL → SALT + H2

2. ACID + METAL OXIDE/HYDROXIDE → SALT + H2O

3. ACID + METAL CARBONATE/HYDROGENCARBONATE → SALT + H2O + CO2

dissociation

when acids are placed in solutions, they split up into their ions, hydrogen ions and anions