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In Lab 9, students performed acid-base titrations. Redox reactions can also be used in titrations.
An example is the titration of ascorbic acid (H2C6H6O6) in lemon juice using triiodide (I3– ). A
starch indicator will turn the solution blue-black at the endpoint. The half-reactions involved are
shown below.
C6H6O6 + 2 H + + ? H2C6H6
+0.06
–
2e
O6
V
?–
+0.53
I3– + 2 e–
3I
V
(a) What is the net redox reaction that occurs? (Use the lowest possible coefficients. Omit statesof-matter from your answer.)
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(b) What is the stoichiometry of H2C6H6O6 to I3–?
3:1 8:3 2:1 1:1 1:2 3:8 1:3
(c) Use the data given below to determine the amount of ascorbic acid in lemon juice. (Note: The
recommended daily allowance of ascorbic acid (Vitamin C) is 90 mg.)
Data Table P6: Titration of ascorbic acid in lemon juice with
triiodide
concentration of I3–
0.0210 M
volume lemon juice
83.44 mL
mass lemon juice
84.94 g
–
equivalence volume of I3
14.93 mL
–
mmol of I3
mmol
mmol of H2C6H6O6
mmol
mass of H2C6H6O6
mg
Determine the errors (if any) with each galvanic cell set-up when the anode is on the left. (Select
all that apply.)

There is nothing wrong with this diagram. The electrodes are in the wrong solution. The
electrons are traveling the wrong direction down the wire. The salt bridge ions are migrating to
the incorrect electrode. The electrons are traveling through the salt bridge. The electrodes and
solutions are in the wrong compartment.

There is nothing wrong with this diagram. The electrodes are in the wrong solution. The
electrons are traveling the wrong direction down the wire. The salt bridge ions are migrating to
the incorrect electrode. The electrons are traveling through the salt bridge. The electrodes and
solutions are in the wrong compartment.

There is nothing wrong with this diagram. The electrodes are in the wrong solution. The
electrons are traveling the wrong direction down the wire. The salt bridge ions are migrating to
the incorrect electrode. The electrons are traveling through the salt bridge. The electrodes and
solutions are in the wrong compartment.

There is nothing wrong with this diagram. The electrodes are in the wrong solution. The
electrons are traveling the wrong direction down the wire. The salt bridge ions are migrating to
the incorrect electrode. The electrons are traveling through the salt bridge. The electrodes and
solutions are in the wrong compartment.

There is nothing wrong with this diagram. The electrodes are in the wrong solution. The
electrons are traveling the wrong direction down the wire. The salt bridge ions are migrating to
the incorrect electrode. The electrons are traveling through the salt bridge. The electrodes and
solutions are in the wrong compartment.
Consider your experimental results from part A of this lab. Suppose your strongest reducing
agent were added to your strongest oxidizing agent. (Use the lowest possible coefficients. Omit
states-of-matter from your answers.)
(a) Write the half-reaction for your strongest reducing agent.
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Mg ? Mg2+ + 2e1-

Correct.
(b) Write the half-reaction for your strongest oxidizing agent.
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MnO4- + 8H+ + 5e- ? Mn2+ +4H2O
Correct.
(c) Note the number of electrons in each half reaction.
In order to balance the number of electrons lost and gained, the oxidation half-reaction must be
multiplied by and the reduction half-reaction must be multiplied by
(d) Write the net redox reaction.
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Assemble a battery, represented by the diagram below with the cathode in compartment A, with
Sn2+/Sn and Cu2+/Cu couples in which the voltage reads positive. (Use the . Use the lowest
possible coefficients. Omit states-of-matter from your answer.)

(a) What half-reaction occurs in compartment A?
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Sn ? Sn2+ +2eYour answer contains an ambiguous or incomplete reaction equation. Check all the components
on the reactant-side of the equation. Check all the components on the product-side of the
equation.
(b) What half-reaction occurs in compartment B?
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Cu2+ +2e- ? Cu
Your answer contains an ambiguous or incomplete reaction equation. Check all the components
on the reactant-side of the equation. Check all the components on the product-side of the
equation.
(c) Write the net redox reaction.
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Sn + Cu2+ ? Sn2+ + Cu
Correct.

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Additional Requirements 

Level of Detail: Only answer needed 
Other Requirements: This is my last postlab assignment and I can't figure it out. If I can get the answers I'm done with the course, thanks so much!