WHAT HAVE WE SEEN SO FAR IN LAB? Brassing a Penny Reactivity Lab Cost of a Penny BRASSING A PENNY Is brass a compound or a mixture? Explain. Mixture because the atoms of Copper and Zinc are mixing/melting together (physical reaction) and no chemical reactions are happening What is are some reasons we plate metals? Protect them from corrosion Decorative REACTIVITY LAB Reactivity of the Metals Magnesium
Aluminum Zinc Iron Tin Lead Explain why putting zinc into magnesium sulfate would NOT produce a reaction. Zinc is less reactive than Magnesium REACTIVITY LAB Would there be a reaction? Why? a. Al + AgNO 3 > YES, Al is more reactive than Ag
b. Cu + FeSO 4 > NO, Cu is less reactive than Fe c. Zn + PbSO 4 > YES, Zn is more reactive than Ag Indicators of a Chemical Reaction
Bubbles Temperature Change Precipitate/New Solid Solid Disintegrates Odor produced Light emitted Explain how a more reactive metal like zinc can be used to protect a less reactive metal like iron. Give a practical example of this. Sacrificials Hot Water Heater, Etc. REACTIVITY LAB Zinc metal could be used in the process to claim (reduce) many metals
from their ores. List three metals that zinc can replace (reduce). Do metals prefer to be oxidized or reduced? Explain. Oxidized, metals want tend to lose electrons (OIL, oxidation is losing) (Hint: Metal ATOMS start with no charge, and then change to a positive ION or gains positive charge.) Are most metals found in the ground in a pure state (as a metallic element) or as compounds (chemically combined with other elements)? Explain why. They have to be reduced to their pure form, most metals are found in compounds in the ground Predict whether magnesium is more likely to be reclaimed (reduced) from its ore by chemical reduction or electrolytic reduction. Justify your answer. Since Magnesium is above Aluminum, it will be reduced by electrolytic reduction. COST OF A PENNY Mass of Zinc = 2.5 - .07 = 2.43 g Weighed mass of copper after HCl = .07g
Percentage of Zinc in New Penny = 2.43/2.5 * 100 = 97.5% Percentage of Copper in New Penny = .07/2.5 * 100 = 2.5% Cost of Zinc in New Penny = (2.44/454) = .00537 x $1.06 = .0057 Cost of Copper in New Penny = (.07/454) = .0001377 x $1.83 = .00025 NOT IN LAB But, .0057 + .00025 = .00595 cents to make 1 penny Value of Pre-Penny = 3.04/454 = .006696 x $1.83 = .012 cents to make 1 penny NOT IN LAB Takes a little more than 1 penny worth of materials to make 1 penny COST OF A PENNY Why do you think our government switched to a Copper-clad penny? Its cheaper, they last longer, lighter. Explain what happened to the new penny when placed in HCl in terms
of oxidation/reduction and the relative activity of copper and zinc. Zn + 2HCl ZnCl2 + H2 (solid) (liquid) (liquid) (gas) Zinc + Hydrochloric acid Zinc chloride + Hydrogen Zn0 + 2H+1Cl-1 Zn+2Cl2-1 + H20 Zinc (most reactive), Hydrogen, Copper (least reactive) Copper is less reactive than Zinc and Hydrogen, so itll protect the inside and wont react with the acid But Zinc is more reactive than Hydrogen, so it replaces Hydrogen and dissolves creating Zinc chloride and hydrogen gas OIL Zinc is being oxidized RIG Hydrogen is being reduced (why we have hydrogen gas)
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