Chapter 11: Oxidation-Reduction Reactions (4%)

oxidation

(OIL RIG → OIL = “oxidation is loss” of electrons)

Oxidation vs. Reduction

A loss of electrons

Increase in oxidation state

reduction

(OIL RIG → RIG = “reduction is gain” of electrons)

Oxidation vs. Reduction

A gain of electrons

Decrease in oxidation state

oxidation, reduced

An oxidizing agent facilitates the ___________ of another compound & is itself ___________ in the process (i.e. it gains electrons)

reduction, oxidized

A reducing agent facilitates the ___________ of another compound & is itself ___________ in the process (i.e. it loses electrons)

OIL RIG

(Oxidation Is Loss of electrons, Reduction Is Gain of electrons)

mnemonic for remembering how redox reactions work

oxygen (or a similarly electronegative element)

the element that almost all common oxidizing agents contain

metal ions, hydrides (H-)

the 2 elements that almost all reducing elements contain (one or the other)

oxidation number

Represents the # of electrons an atom has gained or lost when forming a chemical bond

Positive integers = the atom has lost electrons compared to its neutral state

Negative integers = the atom has gained electrons compared to its neutral state

0

Name the oxidation number for the following:

any free element or diatomic species

EX: Fe, Li, Ar, N₂, P₄)

(***a free element is considered to be any element in an uncombined state, whether monatomic or polyatomic)

equal to the charge of the ion

Name the oxidation number for the following:

monatomic ion (composed of one atom)

EX: Na⁺, Cu²⁺, Se^2-

+1

Name the oxidation number for the following:

Group 1A metals (alkali metals = Li, Na, K, Rb, Cs, Fr) when in a compound

EX: LiH, NaCl, K₂SO₄

+2

Name the oxidation number for the following:

Group 2A metals (alkaline earth metals = Be, Mg, Ca, Sr, Ba, Ra) when in a compound

EX: CaO, MgCl₂, CaCO₃

-1 (unless combined with an element with higher electronegativity)

Name the oxidation number for the following:

Group 7A/17 elements (halogens = F, Cl, Br, I, At) when in a compound

EX: NaCl, HBr

+1

(because hydrogen is less electronegative than most nonmetals)

Name the oxidation number for the following:

hydrogen (usually → when bonded to nonmetals)

-1

(because hydrogen is more electronegative than metals, forming metal hydrides)

Name the oxidation number for the following:

hydrogen when paired with metals (such as elements in Groups 1A and 2A)

-2

(oxides (O^2-) & water (H₂O))

Name the oxidation number for the following:

oxygen (usually → in oxides & water)

-1

Name the oxidation number for the following:

Oxygen when in peroxides

EX: O₂^-2, H₂O₂, Na₂O₂

+2

(however, in O₂F₂, it has an oxidation # of +1)

Name the oxidation number for the following:

Oxygen when paired with more electronegative elements

EX: OF₂

charge

the sum of the oxidation numbers of all the atoms present in a compound is = to the overall _______ of that compound

oxidation number

Oxidation Number vs. Formal Charge

assumes UNEQUAL division of electrons in bonds

formal charge

Oxidation Number vs. Formal Charge

assumes EQUAL division of electrons in bonds

complete ionic equation

Complete vs. Net Ionic Equation

Accounts for all the ions present in a reaction

aqueous, solid salts

To write a Complete Ionic Reaction, split all __________ compounds into their relevant ions and keep _______ ______ intact

net ionic equation

Complete vs. Net Ionic Equation

Ignore spectator ions to focus only on the species that actually participate in the reaction

subtract, spectator ions, aqueous, solid salts

To obtain a Net Ionic Reaction, _________ the ions appearing on both sides of the reaction, which are called __________ _____.

Then split all __________ compounds into their relevant ions and keep _______ ______ intact

aqueous salts

For reactions that contain no _________ _____, the net ionic equation is generally the same as the overall balanced reaction

solid salt, remain, oxidation number

For double displacement reactions that do not form a _____ ____, there is no net ionic reaction because all ions ________ in solution and do not change __________ _______

dismutation (disproportionation)

A type of redox reaction in which one element is both oxidized and reduced, producing two different products with higher and lower oxidation states, respectively

These are usually accomplished by enzymes

charge, electrons

Titrations

Whereas acid-base titrations follow the movement of protons, redox titrations follow the transfer of _______ (as __________) to reach the equivalence point

voltages

Titrations

Indicators used in redox titrations change color when certain __________ of solutions are achieved

potentiometric titration

Titrations

A form of redox titration in which a voltmeter or external cell measures the electromotive force (emf) of a solution

Uses an indicator electrode and a reference electrode, instead of a visual indicator

Equivalence point is determined by a sharp change in voltage