Redox Reactions Flashcards
refers to a reaction in which a species gains electrons
reduction (GER)
refers to a reaction in which a species gives up or loses electrons
oxidation (LEO)
gets reduced during reaction
oxidizes something else–causes the species giving up the electrons to be oxidized
oxidizing agent
Since electrons cannot be created or destroyed and there can be no isolated loss or gain of electrons, neither oxidation or reduction can occur _______, resulting in an electron transfer between 2 species
by itself
The electrons released during ______ are taken up in the ______ process.
released during oxidation
taken up during reduction
substance that gets oxidized
reduces something else
causes another species to be reduced
reducing agent
an oxidizing agent get _______ and _____ electrons
reduced
gain electrons
a reducing agent gets ______ and _____ electrons
oxidized
loses electrons
the oxidation number of an element in its elemental form =
Ex: N2, O2, He, etc.
zero
The oxidation state of a monatomic ion is the same as its ______
charge
In molecules w/ 2 different elements, the elements w/ the greater ________ is assigned a negative oxidation number = to its charge in simple ionic compounds of the element
electronegativity
Sum of the oxidation numbers = _____ for an electrically neutral compounds and equals the overall charge for an ionic species
zero
Oxidation numbers for alkali metals (group I)
+1
oxidation numbers for alkaline earth metals (group II)
+2
oxidation number for group 3A
+3
Oxidation number for halogens
-1 except when combo’ed w/ an element of high electronegativity
Oxidation number for Oxygen
-2
Oxidation number of Hydrogen when bonded to a more electronegative element (most nonmetals) =
+1
Oxidation number of Hydrogen when bonded to a less electronegative element (most metals) =
-1
a complex redox rxn can be separated into these component rxns
elements other than H and O should be balanced
half reactions
in balancing REDOX rxns, the loss and gain of electrons is indicated where appropriate
charge is then balanced w _____ when in acid or _____ when in base. Elements O and H are then balanced with _____
H+: acid
OH-: base
H20: water
each half-rxn is multiplied by an appropriate factor so that the number of electrons gained _______ those lost
rxns are then combined to form the net rxn
equal
contained system in which a redox reaction occurs in conjuction with the passage of electric current
2 types: galvanic and electolytic
electrochemical cell
2 types of electrochemical cell
galvanic (or voltaic)
electrolytic
electrode at which oxidation occurs in an electrochemical cell (i.e. positive)
anode
electrode at which reduction occurs in an electrochemical cell (i.e. negative)
cathode
2 types of electrochemical cells
both contain two electrodes that serves as sites for oxidation and reduction half rxn
oxidation on the anode (loss of electrons)
reduction on the cathode (gain of electrons)
galvanic and electrolytic cells
in REDOX rxn w/ exothermic and spontaneous half rxns (supply energy and are used to do work)
If only a wire were provided for electron flow b/w 2 electrochemical cells, rxn would stop bc an excess neg charge would build up in the sol’n surroundign the cathode and excess positive charge would build up in sol’n surrounding anode. This charge gradient is remedied by a _______, which permits the exchange fo cations and anions.
salt bridge
this creates a charge gradient that permits the exchange of cations and anions in an electrochemical cell
contains an inert electrolyte
at the same time the anions from the salt bridge (Cl-) diffuse from this of the cell into the sol’n to balance out the charge of the newly created + ions and the cations of this flow into the other sol’n to balance out the charge of the neg ions left in solution
salt bridge
common dry cell battery and the lead-acid storage battery found in cars
galvanic cells
in an electrolytic cell w/ positive delta G and nonspontaneous, _______ is required to induce the reaction
electrical energy
oxidation happens at the ____ of an electrolytic cell
anode
AN OX
reduction happens at the ______ of an electrolytic cell
cathode
RED CAT
electrons flow throguh the wire from the ________ to the ______ in an electrode
anode to the cathode
the species in a rxn that will be oxidized or reduced can be determined from the ______ of each species, or the tendency of a species to acquire electrons and be reduced
measured in Volts
defined relative to the standard hydrogen electrode (0.0 volts)
reduction potential
SI Unit = volts
the more positive the reduction potential, the ________ the species’ tendency to be reduced
greater
reduction potential measured under standard conditions (25 degrees C, 1M concentration for each ion in the rxn, partial pressure of 1 atm for each gas in teh rxn, and metals in their pure state)
standard reduction potential (Ei)
If a species has a large reduction potential, it likes to be reduced and is a strong ___________
oxidizing agent
If a species has a large negative reduction potential, is does not like to undergo reduction, and the equation must be ______ for the rxn to become spontaneous (favored)
flipped
flip the sign on the reduction potential when the reaction is flipped
calculated by standard reduction potentials
describes the difference in potential between two half-cells
Electromotive force (EMF or Ecell)
Equation: Electromotive Force
EMF = Ered + Eox
The standard EMF of a galvanic cell is ______
positive
The standard EMF of an electrolytic cell is ______
negative
When adding standard potentials, do not _______.
multiply by the number of moles oxidized or reduced
