Experiment 2: Chemical Changes

Topics: Chemical reaction, Solubility, Copper Pages: 5 (1345 words) Published: May 17, 2015
Dagondon, Vanessa OlgaDate of experiment: July 1, 2013 Nablo, Janica Mae Date of submission: July 18, 2013
Palmitos, Isabel

Experiment # 2
chemical changes

I. INTRODUCTION
Chemical changes occur when a substance combines with another to form a new substance whether by combination reaction, combustion reaction, decomposition reaction and etc. These changes can be observed by evolutions of gas, appearance or disappearance of a precipitate, evolution or absorption of heat or even change in color. This experiment aims to observe the different chemical changes copper undergoes in different conditions.

II. METHODOLOGY

1. Precipitation of Copper (II) Hydroxide

Materials used: 0.100 M Cu(NO3)2 solution, 250-mL beaker, 6.00 M NH3, watch glass, litmus paper, stirring rod, dropper.

A 10-ml of 0.001 M Cu(NO­3)­­2­­ was measured in a 250-ml beaker. Then, about 0.5 mL of 6.00 M of NaOH was added with constant stirring. Afterwards, observations were noted. Two pieces of litmus paper (red and blue) were placed on a clean dry watch glass and the papers were dampened by created solution with the use of the stirring rod. More NaOH were added until the solution was completely alkaline or basic.

2. Formation of Copper (II) Oxide

Materials used: NaOH and Cu(NO­3)2 solution in the latter activity, stirring rod, 6.00M NaOH, Bunsen burner, dropper.

The created solution in the latter activity was heated in about two minutes with constant stirring. The change in color was noted. The copper (II) oxide precipitates were settled down and the change of color on the precipitate was noted. A few drops of NaOH were added to the solution for testing. The solution was again heated until such time that the precipitated changed its color.

3. Conversion of Copper (II) Hydroxide to Copper (II) Sulfate

Materials used: The solution from the previous activity, filter paper, Erlenmeyer flask,6.00 M H2SO4, stirring rod,10 mL water.

The precipitate settled down until the supernate was clear. Then it was through a filter paper into the Erlenmeyer flask. The precipitate was washed in the beaker using 10 mL of water. The precipitate settled down and was decanted again through the filter paper into the Erlenmeyer flask containing the filtrate. The whole process was repeated until the precipitate is washed four times. The same filter paper was washed with about 1 mL 6.00 M H2SO4 and then the filtrate was caught in the beaker containing the copper (II) oxide precipitate. Then the solid was dissolved by stirring. More H2SO4 was added to dissolve the precipitated completely. The filter paper was washed again with 10 mL water. Then observations were recorded.

4. Reduction of Cu (II) Ions to Metallic Copper

Materials used: solution from the previous activity, 1.5 g Zn dust, 6.00 M NH3, of 0.100 M Cu(NO3)2, Water, 6.00 M HCl, filter paper, beaker. About 1.5 g zinc dust was slowly added to the solution in the previous activity with constant stirring. The chemical changes were observed and noted. It stirred until no reaction is occurring and then more zinc was added to make the solution color less. The completeness of the reaction was tested by adding a few drops of the solution in a test tube containing 1 mL of 6.00 M NH3.This solution was compared to the controlled solution(prepared by adding a drop of 0.100 M Cu(NO3)2 solution and 2 drops of NH3 to 1 mL water). Observations were noted. The supernate in the latter step was decanted and discarded and the precipitate was washed in the beaker twice using 10 mL water. The wash water was decanted and discarded after each washing. A 10 mL water and a 2 mL 6.00 M HCl were added to the precipitate slowly. It was stirred until no more change is observed. The precipitate was settled and the supernate was again decanted and discarded. The precipitate was washed again with 10 ml of water. The wash water was again decanted and discarded. The entire solid (precipitate) was...

References: [1] http://www.ccchemistry.us/ch%20111%20experiment%208.pdf
[2] http://dwb.unl.edu/Chemistry/microscale/MScale04.html
[3] http://web.lemoyne.edu/~giunta/chm151L/copper.html#reactions
[4] http://chemmovies.unl.edu/chemistry/smallscale/SS016.html
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