posted by jo on .
I just did an online chemisty lab for Oxidation States of Manganese and I'm stuck. I have three test tubes that have been prepared as follows: Tube 1- Starting PH 13.82 2 mL of KMnO4 1 mL of NaOH Tube 2- Starting PH 7 2 mL of KMnO4 Tube 3- Starting PH 0 2 mL of KMnO4 1 mL of H2SO4 I then added five 1 mL increments of NaHSO3to each of the tubes and the reactions are as follows. Tube 1 - Started as green and turned light green as NaHSO3is added. PH 13.65, 13.65, 13.48, 13.13.41, 13.35 Tube 2 - Started as purple with a brown precipitate. Solution turns almost clear as NaHSO3 is added. PH 7.31, 7.38, 7.41, 7.38, 7.35 Tube 3 - Solution stayed purple and turned light purple with last addition of NaHSO3. PH 0,0,0,0,.14. What oxidation states did the MnO4- and HSO3- ions change in each test tube? Write the net ionic equations for the redox reaction in each test tube.
Already Tried: I'm not sure, but the green color in test tube #1 indicates MnO4-- which has the oxidation state of +6. The purple color of test tube #2 indicates MnO2 which has the oxidation state of +4. And the light purple color in test tube #3 indicates MnO2- which has the oxidation state of +2. Also, I tried coming up with the equation for each test tube, but probably didn't do them correctly: Test tube #1: KMnO4+NaOH+NaHSO3=KSO4+Na+MnO4+H2O Test tube #2: KMnO4+NaHSO3=KHSO3+NaMnO4 Test tube #3: KMnO4+H2SO4+NaHSO3= MnSO4+KSO4+NaSO4+H2O Concerning the oxidation states of H2SO4 in each test tube, I have no idea. Then comes the net ionic equation for each test tube. These I couldn't do because I wasn't sure that the equations were correct. Please help.
This may help.
MnO4^- has Mn in oxidation state of +7. It is purple.
MnO4^-2 has Mn in oxidation state of +6. It is green.
MnO2 has Mn in oxidation state of +4. It is a dark brown ppt.
Mn^+2 has Mn in oxidation state of +2. It is faintly pink.
The HSO3^- has sulfur in oxidation state of +4. It goes to +6 in all of the test tubes.
I found this on the following on the web.
Then if I have the balanced equations of:
2 MnO4- + 2 OH- + SO32- --> 2 MnO42- + SO42- + H2O
2 MnO4- + 3 HSO3- --> 3 SO42- + H2O + 2 MnO2 + H+
2 MnO4- + 5 HSO3- + H+ --> 5 SO42- + 3 H2O + 2 Mn2+
HOw do I do the net ionic equations?