chemistry - oxidation and reduction test

what are oxidation and reduction (redox) reactions driven by?

a change in charge (the gain and loss of electrons)

what happens to electrons during oxidation?

electrons are lost and it becomes more positive

what happens to electrons during reduction?

electrons are gained and it becomes more negative

what has to be known in order to determine which substance was oxidized and which was reduced

the charge of each substance

the sum of all charges in a compound equals….

zero

the sum of all charges in a polyatomic ion equals the….

charge of the polyatomic ion

uncombined elements have a charge of…

zero

ex. Na(s) and O2

if an element has only one charge listed on the periodic table, then that is its….

oxidation number

ex. Na has one charge, 1+ Ca has one charge, 2+ Al has one charge, 3+

when a nonmetal atom is the negative ion in an ionic compound, then the ____________ listed is its oxidation numebr

top charge

ex. NaCl, Cl is anion so its charge is -1

ex. Li3N, N is the anion so its charge is -3

If an element has more than one charge listed, use the other _______ to figure it out

charges

ex. Fe(NO3)2 —— NO3 has a -1 charge, oxygen has a -2 charge, so the N must be +5

NO3 = (5+(-2×3)) = -1

Fe must have a +2 charge to make the compound neutral

Hydrogen is +1 except when combined with a ________, then it is -1

metal

ex. NaH and CaH2

oxygen is -2 unless in a _______ or with ______

peroxide, flourine

ex. H2O2, Na2O2

how do you know if the species is oxidized?

if the charge becomes more positive going from left to right and loses electrons

how do you know if the species is being reduced?

the charge becomes more negative going from left to right and gains electrons

L -

E -

O -

-Lose

-electrons

oxidation

G-

E-

R-

-gain

-electrons

-reduction

add electrons to _______ the _______ on either sifde of the half reaction equations

equal, charges

what side will the e- always be placed on?

the side with the positive charge

in redox reactions, ions that do not change charge during the reactioon

spectator ions

what is the net ionic reaction and how is it written?

the reaction written without the spectator ions. only the substances being oxidized or reduced are included - a combination of each half reduction

the higher up on table J, the more ___ the metals

reactive

for metals, more reactive means more likely to be…..

oxidized

the ability for ______ to oxidize is the basis for lithium batteries

lithium

for nonmetals, more reactive means more likely to be….

reduced

the study of converting

chemical energy into electrical energy and the conversion of electrical energy into chemical energy.

electrochemistry

what energy to voltaic cells convert?

chemical energy to electrical energy

A redox reaction whose two half reactions are carried out separately, and the electrons given off by the oxidation half-reaction are used to power a device, and then given to the reduction half-reaction (batteries are a good example).

voltaic cells

each half reaction is carried out in a half-cell. in these cells, the uncombined free element acts as the _______ which is immersed in a solution of the ion of that element

electrode

these half cells are connected at their electrodes by a wire that is used to transport the electrons from the _______ electrode to the ______ electrode

oxidized, reduced

hooked up to the wire between the two half-cells s the _______ which measures the ____________________ by the difference in oxidation potential and reduction potential of the two electrodes

voltmeter, potential difference

connecting the half-cells is a ______ that is used to complete the circuit. it is made of a porous substance that contains a salt with a different cation than the electrode cations

salt bridge

define: the oxidation half cells of an electrochemical cell

anode

the reduction half cell in an electrochemical cell

cathode

electrons travel from the _______ to the _______ (from loss to gain, from oxidation to reduction) across the wire

anode, cathode

anions travel across the saltbridge from the _____ to the _______

cathode, anode

the conversion of electrical energy into chemical energy (opposite of a voltaic; promotes a non-spontaneous reaction)

electrolysis

in a voltaic cell is energy required or produced?

producedin

in a electrolytic cell, is energy required or produced>

required

in an electrolytic cell, the less active metal is being oxidized. oxidation still occurs at the ______ and reduction still occurs and the ______

anode, cathode

this type of cell uses a battery/power source

electrolytic cell

voltaic cell

1. anode and cathode in same container

2. chemical energy —> electrical energy

3. more active substance is oxidized

4. spontaneous

5. common use: batteries

   1. produces current

electrolytic cell:

1. anode and cathode in separate containers

2. electrical energy —> chemical energy

3. less active substance is oxidized

4. non-spontaneous

5. common use: electroplating

   1. requires current