redox

what do redox rxns involve

oxidation and reduction rxns

what is oxidation

loss of e-

what is reduction 

gain of e-

what is a simple way to remember what happens to e- during redox

oil rig 

what is the reductant or reducing agent

cause another species to be reduced.

what is the oxidant or oxidising agent

cause another species to be oxidised.

when does a metal displacement rxn occur 

when a solid metal is added to an ionic metal solution 

when do halogen displacement rxns occur

when a halogen is added to an ionic solution containing a different halogen ion

what is an oxidation state or number

indication of the number of electrons an atom would gain or lose to get to its present state

what are the rules for oxidation numbers 

1. oxidation state of any element is zero 

2. oxidation state of a monatomic ion is the same as the charge on the ion

3. oxidation state of hydrogen in compounds is always +1, except when forming metal hydrides it becomes -1

4. oxidation state of oxygen in compounds is always –2, except for:

   peroxides where oxidation state = –1 and F₂O, where it is +2

5. in a neutral compound the sum of the oxidation states of the individual atoms must total zero.

6. in ions, the sum of the oxidation states must always equal the charge on the ion.

what are the rules to write half-equations 

1. balance all atoms other than hydrogen and oxygen.

2. balance the oxygen atoms by adding water molecules

3. balance the hydrogen atoms by adding H⁺ ions

4. balance the charge by adding electrons, take into account any charged species.

what do the species with a postive e0 undergo

reduction

what do the species with a negative e0 undergo

oxidation

what does it mean if the overall e0 is greater than 0

then the rxn will occur spontaneously 

what does it mean if the overall e0 is less than 0

then the rxn is non-spontaneous 

what is chemical stability

about electrons and their arrangement, especially valence electrons.

what is the ionisation energy

energy required to remove one electron from a gaseous species

what is first ionisation energy 

energy required to remove one electron from a gaseous atom to form a gaseous ion

what is second ionisation energy

energy needed to remove another electron from the resulting ion

what is corrosion

when a metal oxidises in the presence of air to form a metal oxide

what is rust

hydrated iron(III)