Chem Test

Oxidation

the loss of one or more electrons from a substance

reduction

the gain of one or more electrons

oxidation and reduction always occur…

together

oxidation in its simplest level,

can also be considered as a reaction in which a substance combines with oxygen (gains oxygen)

reduction in its simplest level,

can also be considered as a reaction in which a substance removes oxygen

oxidation number

a concept that provides a way to keep track of electrons in redox reaction according to certain rules

When combined oxygen always has an oxidation number of +1 except

in H2O2 (-1) and OF2/F2O (+2)

Hydrogen always has an oxidation number of +1 except when

it is part of a metal hydride Ex: NaH, CaH2 (-1)

When an element is oxidized its oxidation number

increases

When an element is reduced its oxidation number

decreases

oxidizing agent

a substance that is able to oxidize other substances (the oxidizing agent itself undergoes reduction)

reducing agent

a substance that is able to reduce other substances (the resting agent itself undergoes oxidation)

voltaic cell

a device used to obtain electrical energy from a spontaneous chemical reaction (also known as ‘galvanic cell”)

Each beaker in a voltaic cell is called a

half-cell

oxidation occurs in the half-cell on the

left side of the diagram

reduction occurs in the half-call on the

right side of the diagram

electrodes:

the solid metals that serve to transfer electrons from one half-cell to another (a conducting wire connects the electrodes)

anode:

the negative electrode in the half-cell where oxidation occurs

cathode:

the positive electrode in the half-cell where reduction occurs

salt bridge:

completes the circuit by preventing the build-up of charge by allowing ions to flow from one solution to another (glass tub fillies with a saturated solution of KNO3 gel)

voltmeter:

measures the potential difference in volts (V).