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Level 131

Redox Reactions


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oxidation
addition of oxygen or loss of electrons
Reduction
Cathode is the (oxidation or reduction) part of the reaction?
water and oxygen
what is required for rusting reactions?
barrier
oil, grease, paint or varnish prevent the oxidation of iron by making a _______ to oxygen?
galvanising
adding a layer of zinc over the surface of iron objects is called?
sacrificial protection
attaching large ;umps of magnesium to an iron object is called?
OIL RIG
Oxidation Is Loss (of electrons) Reduction Is Gain (of electrons)
Oxidation state
The number of electrons lost or gained by an atom in a compound
Oxidising agent
A reagent that oxidises (remove electrons from) another species
Redox reaction
Reactions in which electrons are transferred from one species to another
Reducing agent
A reagent that reduces (adds electrons to) another species
Electrons for final equation?
Multiply them so they are equal in each half equation so they cancel out
Equal on both sides
In half equations charges must be...
MnO4-
Manganate ion symbol
Steps for redox reactions
1)Add water 2)Add H+ 3)Balance 4)Add electrons
0
Compounds have a oxidation state of
Hydrogen oxidation state
+1 (except in metal hydrides)
Always +1
Group 1 oxidation state
Always +2
Group 2 oxidation state
Always +3
Aluminium oxidation state
Oxygen oxidation state
-2 (except in peroxides where it's -1, and compounds with OF2 where it is +2)
Always -1
Fluorine oxidation state
Chlorine
-1 (except in compounds with F and O, where it has positive values)
Oxidation 2
Gained oxygen or lost hydrogen
Reduction 2
Lost oxygen or gained hydrogen
Mn²+
MnO4- is reduced to
Manganate ion full equation
MnO4- + 8H + 5e- --> Mn²+ + 4H2O
Redox reactions involve
changes in oxidation number or ionic change
what happens in a oxidation half-reaction
the oxidation numbers of an atom changes in a positive direction
reducation
the gain of electrons in a chemical process
the oxidation number of an atom changes in a negative direction
what happens to the oxidation number of an atom in a reduction process?
Oxidizing agent
An element/compound that's reduced.
describe a single replacement reaction
in a reaction of this type, a free element reacts with a compound to produce a new compound and a new free element
simple table, called an activity series
predicting whether or not a proposed single replacement reaction will occur requires only the use of a_
what the activity series displays?
it displays the relative ease of oxidation of various metals and hydrogen, as determined by the experiment
an element higher on the series is more_and will_
active (loses electrons more easily or it is more easily oxidized)
Oxidation numbers (+/- n)
what we use to keep track of electron trafficking in redox reactions?
oxidation number
charge that atom in a molecule is going to have if electrons are completely transferred
transfer electrons
what are the 2 types of reactions?
double replacement reactions
what are the types of reactions that do not transfer electrons?
how to detect reactions that transfer electrons? what is the name given to this type of reactions?
by noticing Change of charge in the species comparing the reactants and products sides (Change in oxidation number)
they remain the same oxidation numbers comparing the reactants and the products
what happens to the oxidation number when a reaction that does not transfer electrons occur?
loose of electrons
oxidation reaction involves the_electrons
the reducing agent
a reactant that became oxidize is called_
reducing agent induces
the reduction (gain of electrons) to another substance
oxidation reactions and reducing reactions are_
coupled reactions (one cannot happen if the other does not happen)
gain of
reduction reactions involve_electrons
the oxidizing agent
if a reactant becomes reduced is called_
oxidizing agent induces_
the loose of electrons of the other substance (induces to become oxidized)
loose electrons
metals tend to_
gain electrons
nonmetals tend to_
OIL RIG
Oxidation
the reducing agent because it became oxidized
If the oxidation number of an element in a reaction increases (becomes more positive or less negative) it means it is_
the oxidizing agent because it became reduced
If the oxidation number of an element in a reaction decreases (becomes less positive or more negative) it means it is_
There was no electron transfer
what happens if there is not change in the oxidation number of the elements involved in the reaction? (2)
Whenever a substance is oxidize_(regarding oxidation number)
there is always an increase in oxidation number (become more positive or less negative)
Whenever a substance is reduced_(regarding oxidation number)
There is always a decrease in oxidation number (become less positive or more negative)
empirical formula
simplest whole number ratio of each kind of atom in a particular compound
the empirical formula
unit formula is the same as_why?
Elements at the top of the activity series are more_.why?
reactive than any of the elements at the bottom of them.
Dichromate Cr2o7 2-
Orange ,clear solution
green
Chromium Ion Cr3+
Pale green
Flame colour of Barium
Iron(III) Fe3+
Pale orange
Orange-brown
iodine solution I2
yellow
chlorine gas or water Cl2
Red-brown
Bromine water Br2
copper solid
pink orange
blue
Copper ion
the oxide ion
black with copper, white with magnesium
purple
CV^(+) is _______
brown
Nitrogen dioxide gas NO2
Orange brown
Iodine solid I2
Water
In a neutralisation reaction, the products are salt and .................
Iodide ion
Iodine is reduced to
carbon dioxide gas
CO is oxidised to
Hydrogen gas
ACID + METAL --> SALT + ?
Water`
Hydrogen peroxide is reduced to
Hydrogen ion H+ acid
Hydrogen gas is oxidised to
oxide ion
gain of two electrons
poo
brown
Carbon is oxidised to
carbon dioxide or monoxide
SO4 2-
Electrochemical Series (Anions)
bromide ion
Bromine is reduced to
iodine solution
Iodide is oxidised to
sulfur
hydrogen sulfide is oxidised to
Oxygen
1s2 2s2 2p2
chloride ion
Chlorite OCL is reduced to
the manganese ion
permanganate is reduced to
bromine solution
Bromide ion is oxidised to
Iron (II)
Iron (III) is reduced to
chromium ion
Orange dichromate is reduced to
nitrogen dioxide
nitric acid HNO3 is reduced to
oxidized
in becoming ions, metals are
simultaneous
oxidation and reduction are always
redox reactions
reactions in which electrons are transferred between reactants
0
oxidation number of all non-charged atoms
its ionic charge
oxidation number of any monatomic ion
1
oxidation number of group 1A elements
2
oxidation number of group 2A elements
3
oxidation number of Aluminum
-1
oxidation number of Fluorine
1
Hydrogen's oxidation number if combined with non-metals
-2
Oxygen's oxidation number in most compounds
when an atom is oxidized
loses electrons, becomes more positive, has a higher oxidation number
when an atom is reduced
gains electrons, becomes more negative, has a lower oxidation number
Reduced
Oxidation Agent
high electronegativity (attract electrons easily)
strong oxidizing agents (reduced) tend to have
strong reducing agents tend to be
high on the activity series (give up electrons easily)
types of redox reactions
direct combination, decomposition, single replacement,
0
sum of oxidation numbers of ions in a compound equals
relative reactivity
activity series ranks metals according to their
single replacement reactions do not occur when
the ion is above the element on the activity series
Electrochemistry
Any chemistry that produces electricity
produced
in spontaneous redox reactions, energy is
transfer of electrons
energy is released in spontaneous redox reactions in the
Anode
A positive electrode
Cathode
A negative electrode
the anode to the cathode
in a voltaic cell, electrons move from
negative
at the beginning of a redox reaction, the charge of the anode is
Positive
Anode (Electrolytic Cell)
ions
at the anode, atoms become
higher on the activity series
in a spontaneous redox reaction, the metal at the anode of a voltaic cell is
Electrode
a metal strip that conducts electricity
become neutral and solidify
as electrons flow to the cathode, positive ions
liquify
as atoms at the anode become ions, they
how the cathode gets a negatively charged surface
all the metal ions have been reduced, but the cathode continues to receive electrons
salt bridge
_______ allows ions to flow between the cells to balanced the charge in the half-cells.
soluble
A substance that can dissolve is said to be _______.
Cation
(+) Lose an electron
Anion
(-) Gain an electron
cations form
at the anode compartment in a voltaic cell
Electromotive Force (emf)
Another term for Ecell because the potential difference provides the driving force that pushes electrons through the external circuit
cell potential
describes how vigorous a reaction will be