Problem Set

Lesson 9

 

1. a. Assign oxidation numbers to all the elements in the formulas below

(1) Ga2O3: Ga ____ O ____
(2) Ca(ClO3)2: Ca ____ Cl ____ O ____
(3) PO43-: P ____ O ____
(4) C3H6O3: C ____ H ____ O ____

    b. Circle the oxidized form in the pairs listed.

(1) Cu, Cu2+ (2) O, O2- (3) N3-, N2+ (4) F, F- (5) Fe2+, Fe3+

 

2. For the following reactions,

(a) indicate if it is [yes] an oxidation-reduction reaction or not [no];
(b) write the oxidation number of each element below its chemical symbol; and
(c) indicate what is being oxidized, what is being reduced, the oxidizing agent and the reducing agent. (Show the form of the element. For example, if charged, include ion charge.)

  reaction redox
reaction		 being
oxidized		 being
reduced		 oxidizing
agent		 reducing agent
Ex.
2Na + Cl2 rtarrow.gif (850 bytes) 2NaCl
0 0 +1 -1
yes Na Cl2 Cl2 Na
a.
2Cu + O2 rtarrow.gif (850 bytes) 2CuO
         
b.
HCl + NaOH rtarrow.gif (850 bytes) NaCl + H2O
         
c.
2NaCl + Br2 rtarrow.gif (850 bytes) 2NaBr + Cl2
         

 

 

3. Use the standard oxidation potential (SOP) list in your workbook to determine these.

a. Rank the following by how easily they can be oxidized (1# most easily oxidized).

b. Which of these chemical species can be reduced? Which of these can be most easily reduced?

Chemical

Rank for ease
of oxidation.

 Can be reduced? Most easily reduced?
Zn      
Sn      
Sn2+      
Al3+      
Al      
Au      

 

c. For the following reactions, calculate the voltage from the SOP list. Predict whether the reaction will occur spontaneously. (Yes or No)

d. Which of these reactions work (or qualify) as voltaic cells?

Reaction Voltage Spontaneous? Voltaic cell?
Zn + 2Ag+ rtarrow.gif (850 bytes) 2Ag + Zn2+      
Sn2+ + Cl2 rtarrow.gif (850 bytes) Sn4+ + 2Cl-      
2Br- + I2 rtarrow.gif (850 bytes) 2I- + Br2      

 

4. Draw a voltaic cell for: Zn + Fe2+ rtarrow.gif (850 bytes) Zn2+ + Fe

a. Label anode, cathode, salt bridge, and direction electrons flow.

b. Write the anode half reaction:

c. Write the cathode half reaction:

d. The purpose of the salt bridge is:

 

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E-mail instructor: Eden Francis

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