EXERCISE 9     

Determining the Composition of Copper Oxide

     

     

     

      OBJECTIVES:

     

           1.  To generate hydrogen

     

           2.  To reduce copper oxide

     

     

      Equipment

     

           1.  Wide mouth bottle

     

           2.  drying tube

     

           3.  iron stand

     

           4.  thistle tube

     

           5.  clamps

     

           6.  pneumatic trough

 
      

 

 


Procedure

     

           1.  Weigh approximately 32 g of zinc and place in wide mouth bottle.  Then add 5 ml of ZnSO4 and enough water to cover the zinc.

 

           2.  Heat a 6 inch test tube; allow to cool to room temperature, then weigh to nearest .001 g using the analytical balance.

     

           3.  Add about 1.0 to 1.25 g of CuO to test tube and weigh to the nearest .001 g.  Calculate weight of CuO.  Assemble apparatus as shown in Figure 9-1.  The apparatus must be air tight.  Ask instructor to approve it.  Wrap the wide mouth bottle with a towel and very carefully add 9 M H2SO4 through the thistle tube till a steady flow of hydrogen is produced.  (CAUTION!!!  Hydrogen and air mixture is VERY EXPLOSIVE!)

     

               Allow the hydrogen to displace all the air in the apparatus.  Test for purity of hydrogen.  This is accomplished by collecting hydrogen in test tube by water displacement and igniting it by introducing a wooden splint.  A loud, sharp pop indicated that the hydrogen contains air.  When the hydrogen burns quietly, then it is fairly pure.  Disconnect the rubber tubing and allow the hydrogen to flow over CuO at the end of the test tube for one minute without heating.  (Do not let the glass tubing touch the CuO.)  Then heat the test tube containing the CuO very strongly until all the CuO is reduced as observed by change in color.  Write reaction.

     

           4.  Allow test tube to cool to room temperature and weigh to nearest .001.

     

           5.  Calculate weight of Cu.

     

           6.  Calculate percent of oxygen from data.

     

           7.  Calculate percent of oxygen from formula.

     

           8.  Calculate percent error.

     

           9.  Do not discard the contents of wide mouth bottle in sink.  Your instructor will provide a container for used zinc.

     

 

 


EXERCISE 9

     

     

ANSWER SHEET

     

     

     

      NAME                                                                              SECTION                               DATE                                     

     

     

     

     

      1.  Weight of test tube ................................................................ ___________________________

     

      2.  Weight of test tube + CuO .................................................... ___________________________

     

      3.  Weight of CuO ........................................................................ ___________________________

     

      4.  Reaction:

     

     

     

     

     

      5.  Weight of test tube and contents after heating ................. ___________________________

     

      6.  Weight of Cu ........................................................................... ___________________________

     

 

 

 

      7.  Percent of oxygen from data ................................................. ___________________________

     

 

 

 

 

      8.  Calculate percent of oxygen from formula .......................... ___________________________

     

     

     

     

      9.  Calculate percent error ........................................................... ___________________________