Balanced Formula Lab: The Law Of Conservation Of Mass

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In this experiment, the Law of Conservation of Mass was illustrated by performing a series of 5 reactions, including a precipitation reaction, a decomposition reaction, two redox reactions, and an acid base reaction on a copper wire, called the Copper Cycle. The initial and final mass of the copper were measured and percent recovery was calculated to demonstrate that mass wasn’t created or destroyed. The balanced equations, balanced formula-unit equations, total ionic equations, net ionic equations, and half reaction equations were also determined for their appropriate reactions.
In the first step of the cycle, a copper wire was dissolved by reacting it with 16 M nitric acid. A green solution was formed when the nitric acid was first added
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The following equation was determined for this reaction:
Balanced Chemical Equation: Cu(OH)2(s) + heat → CuO(s) + H2O(g)
The fourth reaction was classified as an acid-base reaction because water was produced as one of the products, and the sulfuric acid was neutralized by the basic copper oxide. The following equations were determined for this reaction:
Balanced Formula Unit: CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l)
Total Ionic: CuO(s) + 2H+(aq) + SO42-(aq) → Cu2+(aq) + SO42-(aq) + H2O(l)
Net Ionic: 2H+(aq) + CuO(s) → Cu2+(aq) + H2O(l)
The fifth and final reaction was also classified as a redox reaction because electron transfer was observed from aluminum to copper ions. Aluminum was observed to have lost electrons, and was hence oxidized, which made it the reducing agent. The copper ions, on the other hand, were determined to have gained electrons, and were reduced, which made them the oxidizing agent. The following equations were determined for this reaction:
Balanced Equation: CuSO4(aq) + Al(s) → Cu(s) + Al2(SO4)3(aq)
Oxidation Half Reaction: Al(s) → Al3+ +
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According to this law, the mass of the copper wire that was used in the first step of the Copper Cycle, should be equal to the mass of the recovered copper. The percent recovery in this experiment was calculated to be __%. While this number was lower than 100%, it still supported the law to a certain degree. While decanting the solution in reaction 3, not enough of the solution was decanted, and small amounts of precipitate were accidentally decanted, which could have resulted in less copper being recovered. Small amounts of copper were also left on the aluminum wire, which led to a lower reading. On the other hand, it’s also possible that the actual amount of copper that was recovered was less than the amount measured, because some amount of copper could have oxidized when the product was dried in the steam bath. The oxidized product, CuO, has greater mass than Cu, and could have caused higher readings than what was actually

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