Canvas . 9:00 AM 491 75-125 re-Lab.docx 0 Pre- Lab 6: Redox Lab 1.(10 points) Ir

Question

Canvas . 9:00 AM 491 75-125 re-Lab.docx 0 Pre- Lab 6: Redox Lab 1.(10 points) Iron can be found in the following oxidation states: 0, +2, and Arsenic can be found in the following oxidation states:-3, 0, +3, and+5 i. What is the oxidation state of As in FeAsO i. What is the oxidation state of Fe in FeAso 2. (20 points) Given the following unbalanced chemical equation, balance the reaction under acidic conditions. Identify which species is being oxidized, which is being reduced, which is the oxidizing agent, and which is the reducing agent. BrO, (aq)+Fe (aq) à Br (aq)+Fe (aq) .(20 points) Using a suitable reference table, write the corresponding half- reactions for the following electrochemical cell and determine the standard cell potential. Identify which cell represents the anode and which represents the cathode. Mg (s) | Mg (aq) Cu (aq) | Cu (s)

Explanation / Answer

1.

(i)

Oxiation state of O = -2

For four oxygens O.S = - 8

Therefore, From the possible oxidation state of Fe and As given,

Oxidation state of As = + 5

And

(ii)

Oxidation state of Fe = + 3

2.

BrO3- + Fe2+ ------------> Br- + Fe3+

+5         +2                      -1       + 3

Therefroe,

Species being oxidised = Fe2+

Species being reduced = BrO3-

Oxidising agent = BrO3-

Reducing agent = Fe2+

Oxidation Half Reaction                   Reduction Half Reaction

(i) Fe2+ -------> Fe3+                         BrO3- --------------> Br-

(ii) To balance oxygen atoms in acidic medium add H2O atoms.

Fe2+ ---------------> Fe3+                   BrO3- ----------> Br- + 3 H2O

(iii) To balance hydrogen atoms in acidic medium add H+ ions.

Fe2+ ----------> Fe3+                        BrO3- + 6 H+ ------> Br- + 3 H2O

(iv) To balance charge add electrons

Fe2+ ------> Fe3+ + e                    BrO3- + 6 H+ + 6 e ---------> Br- + 3 H2O

(v) To equalise electrons in both half reactions,

do OHR * 6 and RHR * 1

6 Fe2+ ----------> 6 Fe3+ + 6 e    BrO3- + 6 H+ + 6 e -----------> Br- + 3 H2O

(vi) Add both half reactions to get balanced equation.

6 Fe2+ + BrO3- + 6 H+ -----------> 6 Fe3+ + Br- + 3 H2O

This is the final balanced equation.

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