Chemistry Redox Reactions

Redox Reaction types

Synthesis

Decomposition

Single Replacement

Combustion

Synthesis

2 or more reactants form 1 product

Decomposition

1 reactant forms 2 or more products

NOA

nonmetal oxide + water = acid

acids (start with H and form H+ ions)

HNO3 nitric acid

MOB

metal oxide + water = base

bases (end with OH and form OH - ions)

KOH Potassium Hydroxide

OIL

Oxidization is loss of electrons

RIG

Reduction is gain of electrons

Element that loses electrons

oxidized

reducing agent

Element that gains electrons

reduced

oxidizing agent

Single Replacement types

metal displacement

hydrogen displacement'

halogen displacement

Metal Displacement

higher metal + ionic compound → lower metal + ionic compound

use activity chart

Hydrogen displacement

metal + H-OH (water) → hydrogen + metal hydroxide

use activity series water rules

Halogen displacement

higher halogen + ionic compund → lower halogen + ionic compound

use halogen activity chart

Combustion

Carbon + hydrogen + O2 → CO2 + H2O

If an element is alone

it’s charge is 0

Balancing Redox reactions in acidic conditions

1. Label the oxidation number of each element in the reaction. Identify the elements changing charge.

2. Write half reactions

3. Balance the elements in half reactions (don’t worry about oxygen yet)

4. Add electrons to each side to balance the charges

5. Balance the electrons by multiplying the entire half reaction if necessary, to make the number of electrons in each half reaction the same.

6. Write the new equation (don’t include electrons)

7. Add H2O molecules to balance the oxygen in the reaction

8. Since it is acidic, ad H+ ions to balance the hydrogen atoms on each side

9. Check that the atoms and charges are equal on each side of the equation

Balancing redox reactions in basic conditions

1. complete all acidic conditions steps

2. add OH- to both sides of the equation to balance the H+

3. Rewrite the equation with H+ and OH- together in water molecules. Cancel out the appropreiate number of water molecules so that water appears on only one side of the reaction.

4. Check that all atoms and charges are balanced on each side of the reaction

Reduction Potential Table

E^o table

if a species is higher on the reduction potential table

it will oxidize a species lower on the table.

Galvanic / Voltaic Cells

remember to add the aq ions ( Zn2+ and Cu2+) without the spectator ion (SO4)

Label the metals with their element and (s)

Anode

oxidized element

always left

Cathode

reduced element

always right

Salt Bridge

KCl

Galvanic cells must be

positive / spontaneous

Line notation

anode (s) | anode (aq) || cathode (aq) | cathode (s)

Zn | Zn2+ || Cu2+ | Cu

Electrolytic Cell

same as galvanic cell except backwards