chem 2.3

Acids

• Proton donors

• Release H+ ions

• Strong acids completely dissociate/ionise in solutions ; all H+ ions are released

• Weak acids partially dissociate/ionise in solutions; few H+ ions released

Bases

• Proton acceptors

• Neutralise acids to form salts

• Alkalis are soluble bases releasing OH- ions

• Strong bases completely dissociate/ionise in solutions ; all OH- ions are released

• Weak bases partially dissociate/ionise in solutions; few OH- ions released

Reactions of acids and bases

• Acid + Base → Salt + Water

• Metal + Acid → Salt + Hydrogen

• Metal oxide or Metal Hydroxide+ Acid → Salt + Water

• Metal Carbonates + Acid → Salt + Carbon Dioxide + Water

Anhydrous Salt

A salt that does not contain water of crystallisation

Hydrated Salt

Salt containing water of crystallisation

Salt

A compound formed when a hydrogen in an acid molecule is replaced by a metal ion or an ammonium ion

Water of crystallisation

The water contained in an ionic lattice

Chemical Yield

Theoretical Yield - mass = moles of limiting reactant x Mr of product expected

Percentage yield= (actual yield ÷ theoretical yield) x 100

Yield is never 100% as

• reactants have not fully reacted

• some chemicals are lost (in atmosphere or in equipment)

Atom Economy

• Measure of proportion of reactant atoms that become part of the desired product

• AE(%)= (Mr of desired product ÷ Sum of Mr of all reactants) x 100

  In industries

• Reactions with low AE are less sustainable; low AE means lots of waste is produced, it costs money and energy to seperate and dispose of waste

Oxidation Numbers

Total number of electrons involved in reactions

RULES:

1. Monatomic and diatomic elements, oxidation states = 0

2. Simple monatomic ions oxidation states is the same as its charge

3. Sum of oxidation states in a compound = 0

4. Oxygen always has an oxidation state of -2 unless in peroxides or bonded to flourine where its +2

5. Hydrogen always has an oxidation state of +1 unless bonded to elements of Group 1 on the periodic table where its -1

6. Roman numerals indicate oxidation states where theyre always positive

Redox Reactions

Oxidation

is

Loss of electrons

Reduction

is

Gain of electrons

Oxidising agents; gain electrons and get reduced

Reducing agents; lose electrons and get oxidised