Module 3
1. Module 3
1.21. Page 3
Module 3—Electrochemical Reactions
Lesson 4 Lab: Oxidation States of Manganese
In this investigation you will use your skills of observation to investigate the changes in oxidation number that can occur with certain transitional metals. In preparation for the investigation, complete SC 3.
Self-Check
SC 3. Complete “Lab Exercise 13.B” and “Analysis” questions a–c on page 586 of the textbook.
Self-Check Answers
Contact your teacher if your answers vary significantly from the answers provided here.
SC 3.
a.
Reaction in Table 3 |
Vanadium Ions in Sequence of Reactions |
1 |
VO3–(aq) |
2 |
VO3–(aq) → VO2+(aq) → V3+(aq) → V2+(aq) |
3 |
V2+(aq) → V3+(aq) |
4 |
VO3–(aq) → VO2+(aq) |
5 |
VO2+(aq) (no change) |
6 |
V2+(aq) → V3+(aq) → VO2+(aq) → VO3–(aq) |
b.
Reaction in Table 3 |
Description of Chemical Change |
1 |
Ammonium vanadate(V) dissociates, thus no chemical change or change in oxidation number occurs. |
2 |
Vanadium is reduced from +5 to +2. |
3 |
Vanadium is oxidized from +2 to +3. |
4 |
Vanadium is reduced from +5 to +4. |
5 |
There is no change in oxidation number. |
6 |
Vanadium is oxidized from +2 to +5. |
c.
Reaction in Table 3 |
Explanation of Chemical Change |
3 |
Vanadium is oxidized from +2 to +3, probably due to exposure to atmospheric oxygen. |
4 |
Vanadium is reduced from +5 to +4, forming VO2+(aq). The blue colour of the VO2+(aq) coincides with the appearance of aqueous iodine, the product of the other half-reaction in the system. Aqueous iodine is brown in colour. The combination of the two colours results in the solution appearing black. |
5 |
There is no change in oxidation number because iodide ions do not react spontaneously with VO2+(aq). |
6 |
Vanadium is oxidized from +2 to +5 forming VO3-(aq), since permanganate ions in acidic conditions react spontaneously with V2+(aq). |
Retrieve your copy of the Module 3: Lesson 4 Assignment that you saved to your computer earlier in this lesson. You will complete Part 1 as you view the virtual investigation “Oxidation States of Manganese.”
View the virtual investigation “Lesson 4 Lab: Oxidation States of Manganese.” Remember to record data and observations as you view the presentation.
Module 3: Lesson 4 Assignment
If you have not already done so, retrieve your copy of the Module 3: Lesson 4 Assignment that you saved to your computer earlier in this lesson. Complete Part 1. You will receive instructions later in the lesson on when to complete the rest of the Lesson 4 Assignment and submit your work to your teacher.