Download Redox Reactions Test Review

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Redox Reactions Test Review
Part 1: Oxidation Numbers
1. What is the oxidation number for any neutral, uncombined element? Zero
2. What is the common oxidation number for oxygen? What is the oxidation number for oxygen in
H2O2 (the exception)? Oxygen is usually a -2, but in H2O2 it is a -1.
3. What is the oxidation number for hydrogen in a metal hydride (ex. NaH, CaH2)?
Hydrogen is usually a +1, but in a metal hydride it is a -1.
4. Assign the oxidation number for each element in the following:
a. N2O4
N = +4
O = -2
b. CO32-
C = +4
O = -2
c. H2
H=0
d. NO2
N = +4
O = -2
e. CrO42-
Cr = +6
O = -2
f. Cr2O72-
Cr = +6
O = -2
g. SO42-
S = +6
O = -2
h. SO32-
S = +4
O = -2
i.
SO3
S = +6
O = -2
j.
SO2
S = +4
O = -2
k. N2
N=0
l.
NO2
N = +4
O = -2
m. NH3
N = -3
H = +1
n. N2O3
N = +3
O = -2
Part 2: Oxidation and Reduction
5. Define an oxidation and reduction (redox) reaction
An oxidation reduction reaction involves the gain and loss of electrons.
6. In oxidation, what happens to the oxidation number? Does the element gain or lose electrons?
In oxidation, the oxidation number gets more positive because electrons are lost. LEO
7. In reduction, what happens to the oxidation number? Does the element gain or lose electrons?
In reduction, the oxidation number gets more negative because electrons are gained. GER
8. In a redox reaction, ClO4-1 is changed to Cl-1.
a. Are electrons lost or gained by chlorine?
Cl goes from +7 to -1, so electrons are gained. GER
b. How many electrons are lost or gained by chlorine?
8 electrons are gained
9. Define spectator ion.
A spectator ion does not change in oxidation number during a redox reaction.
10. In the equation Ni + 2 HCl  NiCl2 + H2 label the following
a. Oxidized: Ni
b. Reduced: H
c. Spectator Ion: Cl
11. In the equation Ca2+ + 2 Li  Ca + 2 Li+ label the following
a. Oxidized: Li
b. Reduced: Ca
12. In the equation 2 C2H6 + 7 O2  4 CO2 + 6 H2O label the following
a. Oxidized C
b. Reduced O