Chemistry: Acids and Bases

Arrhenius acid (definition)

A substance that dissociates (breaks up) in water to produce H+ ions.

Monobasic

One H+ produced

Dibasic

Two H+ produced

Tribasic

Three H+ produced

Strong Arrhenius acids

Dissociate fully in water e.g. HCl to produce H+ ions

Weak Arrhenius acids

Dissociates partially in water e.g. CH3COOH to produce H+ ions

Arrhenius acids note

H+ ions can't exist on their own in water. Bond with a water molecules to form a hydronium ion, H3O+

Arrhenius base definition

A substance that dissociates in water to form OH- ions.

Strong Arrhenius base

Dissociates fully in water to produce OH- ions

Weak Arrhenius Base

Dissociates partially in water OH- ions

Arrhenius base (note)

Arrhenius's theory is limited to bases and solutions that dissolve in water. Not all acid-base pairs need water or involve OH ions

Brønsted-Lowry acid (definition)

A proton H+ donor

Strong Brønsted-Lowery acid

Good proton donor e.g. HCL

Weak Brønsted-Lowery acid

Poor proton donor e.g. CH3COOH

Brønsted-Lowery base

A proton (H+) acceptor

Strong Brønsted-Lowery base

Good proton acceptors. E.g. NaOH

Weak Brønsted-Lowery base

Poor proton acceptors

Amphoteric substances

Substances that can react as both acids and bases depending on what they react with. E.g. H2O

Arrhenius Vs. Brønsted-Lowry (Arrhenius)

Limited to water reactions, limited to bases that produce OH-. Hydronium ions not taken into account. Can't explain amphoteric substances

Arrhenius Vs. Brønsted-Lowry (Brønsted-Lowry) (4)

Not limited to reactions in water, not limited to bases that produce OH-. Takes hydronium ions into account. Explains amphoteric substances

Conjugate base (definition)

What the acid changes into when it donates a proton

Conjugate acid (definition)

A base turns into its conjugate acid when it accepts a proton

Conjugate acid-base pair (definition)

Any pair of an acid and a base that differ by a proton

Salt (definition)

The substance formed when the H+ from an acid is replaced with metal or ammonium ion

Neutralisation (definition)

The reaction between an acid and a base to form salt and water

First type of neutralisation

Acid + metal —\> salt + hydrogen

Second type of neutralisation

Acid + Base —\> salt + water

Third type of neutralisation

Acid + carbonate —\> salt + water + carbon dioxide

First example of neutralisation in life

Medicine, extra HCl causes heartburn. Gaviscon contains a base to neutralise the acid (sodium hydrogencarbonate)

Second example of neutralisation in life

Agriculture, if soil is too acidic, lime (CaO) added to neutralise acid. Lime + water\= calcium hydroxide (base)