This document discusses identifying redox reactions using oxidation numbers. It provides examples of assigning oxidation numbers to determine if a reaction is redox. A redox reaction is identified when oxidation numbers change for an element. The first reaction provided is a redox reaction where bromine is oxidized and chlorine is reduced. The second reaction shown is determined to not be a redox reaction because no oxidation numbers change. Multiple choice questions are given at the end to test identifying redox reactions.

1. REDOX REACTIONS USING
OXIDATION NUMBERS

2. Identifying Redox Reactions
The change in oxidation number can be
used to identify whether each reaction is a
redox reaction or a reaction of some other
type.
If a reaction is a redox reaction, identify the
element reduced, the element oxidized.
a. Cl2(g) + 2NaBr(aq) → 2NaCl(aq) + Br2(aq)
b. 2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l)

3. Applying oxidation numbers to the equation
a. Assign oxidation numbers.
0 +1 –1 +1 –1 0
Cl2(g) + 2NaBr(aq) → 2NaCl(aq) + Br2(aq)
If changes in oxidation number occur, the
reaction is a redox reaction

4. The oxidation numbers have increased and decreased for
bromine and chlorine respectively
• This is a redox reaction.
• The chlorine is reduced.
• The bromide ion is oxidized.
0 +1 –1 +1 –1 0
Cl2(g) + 2NaBr(aq) → 2NaCl(aq) + Br2(aq)

5. Let us look at another example.
Assign oxidation numbers.
+1 –2 +1 +1 +6 –2 +1 +6 –1 +1 –2
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l)

6. Calculate the change (if any) in the oxidation numbers
• There was no change in any of the elements oxidation numbers.
• This is not a redox reaction.
+1 –2 +1 +1 +6 –2 +1 +6 –1 +1 –2
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l)

7. Which of the following are redox reactions?
1. NH3 + HCl → NH4Cl
2. SO3 + H2O → H2SO4
3. NaOH + HCl → NaCl + H2O
4. H2S + NHO3 → H2SO4 + NO2 + H2O

8. Did you get them correct?
1. NH3 + HCl → NH4Cl
2. SO3 + H2O → H2SO4
3. NaOH + HCl → NaCl + H2O
4. H2S + NHO3 → H2SO4 + NO2 + H2O