I need help with 3 main ideas for a aluminum and copper chloride lab. I need evidence for these 3 ideas that what happened was a chemical reaction.
Change in mass, change in color, change in temp, change in ...
Aluminum metal usually has a passivating layer of Al2O3 which prevents aluminum from reacting with Cu2+ ions. Al won't react with CuSO4(aq), for instance. But if NaCl is added then it will. It is the effect of the chloride ion that makes the reaction go. Al2O3(s) + 8Cl-(aq) + 3H2O -- 2[AlCl4]^- + 6OH- Once the passivating layer is dissolved, then aluminum metal is available to react with chloride ion. You see the aluminum metal disappear, while dark red Cu metal is formed, along with the decrease in the blue color due to hydrated copper ions, [Cu(H2O)6]^2+. In addition, aluminum metal has a side-reaction with water to form hydrogen gas. Therefore, you will observe that as gas is given off. Not only that, the temperature of the solution will increase. 2Al(s) + 2OH- + 6H2O -- 2[Al(OH)4]- + 3H2(g) In summary. There are four indicators of a chemical reaction. 1. The formation of a precipitate 2. The evolution of a gas 3. A color change 4. A temperature change. All four indicators are observed. Solid Cu metal is formed. Hydrogen gas is given off. The color of the solution changes from blue to colorless, and the temperature increases.
