OXIDATION- REDUCTION [6]

Oxidation-Reduction (Redox) Reactions

- A reaction that involves the transfer of electrons between chemical species (the atoms, ions, or molecules involved in the reaction).
- The burning of fuels, the corrosion of metals, and even the processes of photosynthesis and cellular respiration involve oxidation and reduction.

Oxidation

LOSS of electrons

Reduction

GAIN of electrons

Reducing Agent

LOSS of electrons in a?

Oxidizing Agent

GAIN of electrons in an?

The oxidation number (ON) of an uncombined element is always zero.
Example: Na

RULES FOR ASSIGNING OXIDATION NUMBERS:
#1

A monatomic ion has an oxidation number equal to its charge.
Example: Na+, Cu+2, N3-

RULES FOR ASSIGNING OXIDATION NUMBERS:
#2

The oxidation numbers of hydrogen is +1 with non-metals and -1 with metals.

RULES FOR ASSIGNING OXIDATION NUMBERS:
#3

The oxidation number of oxygen is usually -2, except in peroxides (X2O2 or compounds containing O2 2- ) where oxygen has an oxidation number of -1.

RULES FOR ASSIGNING OXIDATION NUMBERS:
#4

Group IA (Alkali Metals): always +1
Group 2A (Alkaline Earth Metals): always +2

RULES FOR ASSIGNING OXIDATION NUMBERS:
#5

Fluorine has an oxidation number of -1 in all compounds; other halogens (Cl, Br, I) usually have ON of -1 unless combined with oxygen or fluorine where it is a positive number.

RULES FOR ASSIGNING OXIDATION NUMBERS:
#6

Oxidation

An INCREASE in oxidation number of an atom signifies?
(Example: from 0 to +2)

Reduction

A DECREASE in oxidation number of an atom signifies?
(Example: From +1 to 0)

Permanganometric Titrations

- Used to measure the amount of analyte present in the unknown chemical sample using permanganates as titrant.
- Involves two steps: standardization of potassium permanganate solution using standard sodium oxalate and titration of the analyte using potassium permanganate solution

Iodimetry

When a reducing analyte is titrated with iodine (the titrant), the method is called?

At the Start

IODIMETRY
When to add indicator?

Direct Titration

What type of Titration is Iodimetry?

Iodometry

When an analyte that is an oxidizing agent is added to excess iodide (I - ) to produce iodine (I2), and the iodine produced is determined by titration with sodium thiosulfate, the method is called?

Solution becomes Straw-Colored

IODOMETRY
When to add indicator?

Indirect Titration

What type of Titration is Iodometry?