redox Flashcards
define redox
reduction, oxidation
reaction occur together
smth must oxidise, smth must reduce
oxidise: individual element’s O.S. increases LHS -> RHS
reduces: individual element O.S. decreases LHS -> RHS
oxidation state vs oxidation number in olvl
same thing
any element oxidation state
always 0
ELEMENT HAVE NO CHARGE.
any ion oxidation state
charge, ion
i.e. Iron (II) oxidation state: +2
i.e. X 3- oxidation state -3
1 unit oxygen oxidation state (bonded 2 compound)
O: -2
EXCEPT FOR
hydrogen peroxide’s oxygen (H2O2): -1
i.e. Na2 O
Na: +1
Na2: +2
O: -2
O.S.: +2-2 = 0
1 unit hydrogen oxidation state (bonded 2 nonmetal)
+1
1 unit hydrogen oxidation state (bonded 2 metal)
-1
total oxidation state of compound
add up to Zero
total oxidation state of: OH-
NO3 2-
SO4 2-
CO3 2-
NH4 +
total oxidation state = charge
i.e.
SO4 2- total oxidation state: -2
1 unit O oxidation state: -2
4 unit O oxidation state: -8
Therefore, sulfur oxidation state: +6
S2O3 2-
total oxidation state of sulfur
s2o3 2-
total OS oxygen 3(-2) = -6
OS s2 = 2- (-6) = 8
Ans: 8
no need memorise. Just know polyatomic atoms are stuff mashed tgt. with one charge
i.e. XY -, means total OS is -1
but XY means total OS is 0
does molar number (big number) affect oxidation state?
no
to find oxidation/reduction of X3 + y2 = y2x3 , look for:
X3’s OS or X’s OS?
X’s OS
look for it individual to compare (standardized)
to find out which oxidate, reduce, what to find?
- find O.S., all other element beside oxygen
XY individualO.S. of X (LHS) > 2+
XY individual O.S. of X (RHS) > 3+
Did X oxidise, or reduce?
- X in XY oxidised
- Oxidation State of X increases from 2+ to 3+ in XY
XY individual O.S. of Y (LHS) > 2-
XY individual O.S. of Y (RHS) > 3-
is Y
- Y in XY reduced
- Oxidation State of Y decreases from 2- to 3- in XY
