Transcript Redox - Xavier High School

Redox
Assign oxidation
numbers to reactant
and product species.
•Define oxidation and
reduction.
Reduction of Iron Ore
•Explain oxidationreduction reactions
(redox reactions).
Oxidation of Copper
Oxidation and reduction reactions:
what the gosh darn heck are they?
Oxidation: the LOSS of electrons
Reduction: the GAIN of electrons
Redox
LEO the lion says GER!
Loss of Electrons is Oxidation.
Gain of Electrons is Reduction.
OIL RIG
Oxidation Is the Loss of electrons.
Reduction Is the Gain of electrons.
Connection to Electrochemistry
• RED CAT
• AN OX
REDuction occurs at the CAThode.
OXidation occurs at the ANode.
Half Reactions
• Show what happens to electrons in the two parts of
a redox reaction: the reduction and the oxidation
• Steel hulls in ships have zinc blocks attached
because they oxidize and release electrons. These
electrons get consumed by the steel and prevent
corrosion.
Rules for Writing Half-Reactions
Equations
1. The number of electrons gained must equal
the number of electrons lost.
2. The equation must balance with respect to
both atoms and charge.
(Charge and mass are conserved in redox equations.)
Assigning Oxidation Numbers
Write the half-reaction equations for the redox
reaction
Mg (s) + Br2 (l) → MgBr2 (s)
• Step 1: Use oxidation numbers to determine
what is oxidized and what is reduced
0
0
2+ 1Mg (s) + Br2 (l) → MgBr2 (s)
What happened to Mg?
Mg gained a positive charge so it lost electrons.
It is oxidized.
0
0
2+ 1Mg (s) + Br2 (l) → MgBr2 (s)
What happened to Br2?
Br2 got a negative charge so it gained electrons.
It is reduced.
• Step 2 : Write two separate equations: one
showing oxidation and another showing
reduction. Use coefficients to balance the
number of atoms.
Mg → Mg2+
Br2 → 2Br-
Step 3: Make the charge balance in each
equation by adding electrons.
Mg → Mg2+ + 2eBr2 + 2e- → 2Br-
Check:
1. The number of electrons gained must
equal the number of electrons lost.
2. The equation must balance with respect
to both atoms and charge.