Introduction: The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction. If we account for all reactants and products in a chemical reaction, the total mass will be the same at any point in time in any closed system. http://www.nature.com/scitable/knowledge/library/the-conservation-of-mass-17395478 Chemical reactions relate to many different relationships and mass relationship is one of the most important coloration. So today’s experiment is going to discover the relationship between mass of Copper(II) Chloride dehydrate and aluminum foil. In this experiment, the conditions are not ideal, so there will be limiting reactant and excess reactant. By finding the limiting reactant, it is easy to find the excess reactant and the mass of each reactant. In this experiment, the equation is given and so the mass of each chemical can be determined. So the relationship should be obvious to see. In a chemical reaction, the total atoms will not transform, however, the mass can be affected by the mass of water in the air. According to the conservation of the mass, the atoms will not change, but the mass of each atom will be affected.
Research question: What is the mass produced by the reaction of copper(II) chloride dehydrate and aluminum foil?
Variable: The mass of all the products, the room temperature, the surface area of the aluminum foil, the concentration of the solution, the temperature of the hot plate.
Materials: refer to “Mass relationships in a chemical reaction”
Procedure: refer to “Mass relationships in a chemical reaction”
Data table 1: Mass of chemicals
Copper(II) chloride dehydrate| 2.00±0.01|
Beaker 200mL| 68.18±0.01|
Data table2: Qualitative observations
Before| During| After|
Shiny silver Aluminum pieces. No odor and crystal pieces.| After adding water, the water becomes green and crystals dissolve in the water. After adding the aluminum piece into the liquid, bubbles are produced, the Aluminum pieces turn into reddish brown. Heat is released and steam is on the side of the tube.| The liquid is cloudy grey, not so much Aluminum pieces left in the tube and solid stays on the bottom. Odorless. Mass is 69.28±0.01g.| Solids are dry and the color is reddish brown. Mass is 69.28±0.01g| N/A| Some solids turn into green, some crystals are still reddish brown. Solids are dry and the mass is 68.95±0.01g.|
Limiting reactant: CuCl2 2.00±0.01gCuCl2*1mol CuCl2/134.45g CuCl2*3mol CuCl2/3mol Cu*63.55g Cu/1mol Cu=0.945g Cu Al: 0.00519mol Al/ 2mol Al*3mol Cu/1 mol Cu*63.55g Cu=0.51g
So Al is the limiting reactant
Mass of copper: 69.28±0.01g-68.18±0.01g=1.10±0.02g
(Experimental result / Theoretical result) * 100% = percentage yield 1.10±0.02/0.495g*100%=(2.22±0.040g)*100%=200±4%
Mass of copper after drying: 68.95±0.01-68.18±0.01=0.77±0.02g (Experimental result/ Theoretical result)*100%= 0.77±0.02g/0.495g*100%=(1.56±0.01)*100%=156±1%
The final table of all the data’s
| Number of Moles Used in the Limiting Reactant (Aluminum)| Mass of Copper Formed in the Lab | Mass of Copper Dried Overnight (Experimental Yield)| Theoretical Yield of Copper | Percentage Yield of Copper Formed in the Lab| Percentage Yield of Copper Dried Overnight| Values| 0.00519 mol Aluminum| 1.10 ± 0.02 g Cu| 0.77 ± 0.02 g Cu| 0.495 g Cu| 200 ± 4 %| 156 ± 1%|
Conclusion and Analysis:
According to the experiment, the purpose is to determine the mass of copper formed when excess aluminum is allowed to react with a given mass of a copper salt. The experimental mass of copper without drying overnight is 1.10±0.02g and after leaving it overnight, the mass is 0.77±0.02g. So...