redux

Reactions involving the transfer of electrons

must have a metal and a non-metal for electrons to transfer

Cumbustion reactions are also "Oxidization"

Describes how many electrons have been lost or gained by an atom

we must use oxidation numbers to keep track of the partial gain or loss of electrons by an atom in a molecular compound

1. a metal or a non metal in the free state has an oxidation number of 0

2. A monoatomic ion has an oxidation number equal to it's ionic charge

3. A hydrogen atom is usually assigned an oxidation number of 1+

4.An oxygen atom is ALWAYS assigned an oxidation number of -2

5. For the molecular compouind (covalent/non-metal), the more electronegative element is assigned a negative oxidation number equal to it's sharge as an anion (tricky

6. For an ionic compound, the sum of the oxidation numbers for each of the stoms in the compounds is equal to 0

7. for a polyatomic ion, the sum of the oxidation number for each of the atoms in the compound is equal to the iconic charge on the polyatomic ion

For each molecule, the sum of the oxidation numbers for each of the atoms in the compound is equal to 0

Rules 6,7,8 all the same rule.

Note: If there is a conflict in these rules, the rule with the lowest number has priority!

Seven non metals occur naturally as diatomic molecules

they are: hydrogen (H₂)_, Nitrogen (N₂), Oxygen (O₂), F₂, Cl₂, Br₂, I₂

• A chemical reaction that involves the transfer of electrons in an oxidation reducyion reaction.
• Iron loses electrons Oxidization
• Fe-> Fe²⁺+ 2e^-
• The sulfur gains electrons and is Reduced

Oxidation is the loss of electrons and Reduction is the gain of electrons.

an Oxidizing agent is a substance that causes oxidation by accepting electrons. The oxidating agent is reduced

Is a substance that causes reduction by donating electrons. The reducing agent is oxidized

• "LEO the lion says GER
• L^oss E^lectrons O^xidation
• G^ain E^electrons R^reduction

In a redox reaction, one substance must be oxidized and one substance must be reduced (these always happen simutaneously)

The total number of electrons lost is equal to the total electrons gain

• •We can easily tell that the oxidation number of iron changes from +2 to +3; iron is oxidized.
• •Manganese is reduced from +7 in MnO4- to +2 in Mn2+; manganese is reduced.

When we balance redox reactions, the number of electrons lost must always equal the number of electrons gained

• There are two ways to balance redox reactions:
• 1. The oxidation Number Method
• 2. Half-Reaction Method

• 1. Inspect the reaction and the substances undergoing a change in oxidation number
• a) Write the number above each element
• b) Diagram the number of electrons lost by the oxidized substance and gained by the reduced substance

2. Balanc each element in the equation using a coefficient. Remember , that the electrons lost must equal the electrons gained. If they are not the same, balance the electrons as follows

b)In front of the reduced substance, place a coefficient equal to the total number of electrons lost by the oxidized substance.Balance the remaining elements by inspection

• 3.After balancing the equation, verify that the coefficients are correct.
• a)Place a check mark above the symbol for each element to verify that the number of atoms is the same on both sides.
• b)For ionic equations, verify that the total charge on the left side of the equation is the same as the total charge on the right side of the equation.

an alternative method for balanching redox reactions is the half-reaction method.

a half reaction shows the oxidation or reduction process of redox reaction separately

the oxidation half of the reaction is balanced forst then the reducation half of the reaction is balanced second

1. write the half reaction for both the oxidation and reduction processes separately

• a) identify the reaction that is oxidized and its product
• b) Identify the reactant that is reduced and its product

• Balance the atoms in each half-reaction using coefficients
• a)balance all elements except O andH
• b) balance O using H₂O
• c) balance H using H⁺
• d) for reactions in a basic solution, add one OH-to each side to neutralize each H⁺

Multiply each half-reaction by whole number so that the total # of e^-'s lost by oxidation equal the total# e^-'s gained by reduction

•The oxidation number describes how many electrons have been lost or gained by an atom.

•Reduction is the gain of electrons.

•A reducing agent is a substance that causes reduction by donating electrons. The reducing agent is oxidized.

In redox reactions, the number of electrons lost must equal the number of electrons gained

• –The Oxidation Number Method
• –The Half-Reaction Method