Illustrated Guide to Home Chemistry Experiments

Chapter 10 Laboratory: Reduction-Oxidation (Redox) Reactions 187

SBSTITUTIU oNS ANd modIfICATIoNS

• If you do not have a 0.01 M solution of potassium
  permanganate, make one up by diluting your potassium
  permanganate stock solution as required. Alternatively,
  dissolve 0.08 g of potassium permanganate in about 40 mL
  of water and make it up to 50 mL. (The exact concentration
  is not critical for this lab.)


• If you do not have a bench solution of 1.0 M sodium
  hydroxide, dissolve 4.00 g of sodium hydroxide in 90 mL of
  water and make it up to 100 mL. (Be careful; this reaction is
  extremely exothermic.)


• If you do not have a bench solution of 1.0 M sulfuric acid,
  carefully add 5.6 mL of concentrated (18 M) sulfuric acid to
  90 mL of water and make it up to 100 mL. (Be careful; this
  reaction is extremely exothermic.).


• If you do not have a 0.01 M solution of sodium bisulfite,
  dissolve 0.10 g of sodium bisulfite in 90 mL of water and
  make up the solution to 100 mL.

POCEDURER
1.f you have not already done so, put on your splash I
goggles, gloves, and protective clothing.

2. Label four test tubes A through D, place them in the
   test tube rack, and transfer about 10 mL of 0.01 M
   potassium permanganate solution to each of the tubes.


3. Test tube A will contain only the potassium
   permanganate solution, and will serve as the control
   and example of manganese in oxidation state +7.
   Record the color of this solution on line A of Table 10-3.


4. With stirring, slowly add 0.01 M sodium bisulfite
   solution to test tube B until no further color change
   occurs. Record the color and the presence or absence
   of any precipitate on line B of Table 10-3.


5. Add 8 mL of 1.0 M sodium hydroxide solution to test tube C.

FIGURE 10-2: Oxidation states of manganese

TABLE 10-3. Observe the oxidation states of manganese—observed and calculated data

Test tube ColorPrecipitate?Oxidation state

A. Potassium permanganate only

B. Potassium permanganate + sodium bisulfite

C. Potassium permanganate + sodium hydroxide + sodium bisulfite

D. Potassium permanganate + sulfuric acid + sodium bisulfite

6. With stirring, slowly add 0.01 M sodium bisulfite
   solution to test tube C until no further color change
   occurs. Record the color and the presence or absence
   of any precipitate on line C of Table 10-3.


7. Add 6 mL of 1.0 M sulfuric acid solution to test tube D.


8. With stirring, slowly add 0.01 M sodium bisulfite
   solution to test tube D until no further color change
   occurs. Record the color and the presence or absence
   of any precipitate on line D of Table 10-3.


9. Comparing the appearances of the contents of the
   four test tubes, decide which oxidation state of
   manganese is represented by the contents of each
   test tube and enter that value on the appropriate line
   of Table 10-3.

dISpoSAL: you can flush the dilute solutions used

in this lab down the drain with plenty of water.