Percent Mass of Copper in a Penny Introduction The purpose of this lab is to determine the percent mass of Cu in a penny and see if the fabricator that makes the planchets for the government is using the correct amounts of Cu in the pennies. The composition of a standard penny is 97.5% Zn and 2.5% Cu. In the lab we will be using Beer’s Law (A=elc+b where A is solution absorbance‚ e is a constant called molar absorbency‚ l is the length in cm‚ and c is the concentration). Using Beer’s Law in this
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The headwaters of the Doce River rise in the southeast-east area (SE-E) of the Iron Quadrangle‚ located in south-central portion (C-S) of the state of Minas Gerais (Figure 1). The Iron Quadrangle is historically known as a rich auri-ferriferous province and is a classic region of the world Precambrian geology (Dorr‚ 1959). Its designation results from the area’s planimetric features‚ with a surface area of around 7‚000 km2‚ comprising the most important iron mines of Minas Gerais (Barbosa‚ 1968)
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Mg2+(aq) + 2e– Reduction: Cu2+(aq) + 2e– Cu(s) Overall equation: Mg(s) + Cu2+(aq) Mg2+(aq) + Cu(s) c No reaction. Iron cannot displace the more reactive zinc from solution. d Overall equation: Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s) Review Exercise 9.2 1 a –2 b 0 c +4 d +6 e +6 f –2 2 a NH3‚ ammonium salts b N2 c N2O d NO e HNO2‚ N2O3‚ nitrites f HNO3‚ nitrates 4 a Cr2O72–(aq) + 8H+(aq) + 3SO32–(aq) 2Cr3+(aq) + 4H2O(l) + 3SO42–(aq) b Cu(s) + 2NO3–(aq) + 4H+(aq) Cu2+(aq) + 2NO2(g)
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compound or an item such as a post-1983 penny. The experiment will be using HCl a strong acid to dissolve all the zinc inside the outer copper shell. The reaction follows as such; Zn+2HCLZnCl2+H2‚ but there will be no reaction with copper. The portion that will be measured is the mass of copper left after all of the Zn goes through the reaction process. Hypothesis: If the penny is post-1983‚ then there will be a percent yield of copper greater than 30%. Research Question: What is the percent
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pressure at which one mole of chlorine gas will occupy 22400 cm3 at 0oC. (For chlorine‚ a = 6.49 L2-atm/mol and b = 0.0562L/mol.) (10 marks) 5. (a) The standard potential of Zn2+/Zn electrode is -0.76V‚ and the standard potential of the cell Zn(s)│Zn2+(aq)║Cu2+(aq) │Cu(s) is 1.10V. What is the standard potential of the Cu2+/Cu electrode? (2 marks) (b) What will be the potential if the zinc ion concentration and the copper ion concentration are 0.025M and 0.25M respectively? (5 marks) (c) Calculate
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Topic 10 Rate of Reaction Part A Unit-based exercise Unit 36 An introduction to rate of reaction Fill in the blanks 1 concentration; time 2 instantaneous 3 a) the gaseous product / carbon dioxide evolved b) loss in mass 4 a) colorimeter b) standard alkali c) the gaseous product / carbon dioxide evolved 1 time to reach the opaque stage 5 transmittance; 6 hydroxide; titrimetric True or false 7 T In the oxidation of methanoic acid by bromine‚ the intensity of the orange colour of bromine
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Equations and their Examples: 1. ACID + METAL –––––––> SALT + HYDROGEN Hydrochloric acid + Magnesium Magnesium Chloride + Hydrogen 2HCl(aq) + 2Mg(s) 2MgCl(aq) + H2(g) Sulphuric acid + Zinc Zinc Sulphate + Hydrogen H2SO4(aq) + Zn(s) ZnSO4(aq) + H2(g) Nitric acid + Aluminium Aluminium Nitrate + Hydrogen 2HNO3(aq) + 2Al(s) 2AlNO3(aq) + H2(g) 2. ACID + BASE –––––––> SALT + WATER Hydrochloric acid + Copper II Oxide Copper II Chloride + Water HCl(aq) + CuO(s)
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Potentiometric titration applications general procedure similarities with redox titration INTRODUCTION Determining the endpoint from a potentiometric redox titration curve: EXPERIMENTAL Preparation of Cu/Cu2+ Reference Electrodes 5 cm Pasteur pipet: plugged with cotton saturated KCl/KNO3‚ 0.1 M of CuSO4 solution Copper wire voltmeter Modelling clay EXPERIMENTAL Preparation of KMnO4 weight of KMnO4 = ? 300 mL of 0.01 M solution Dissolve in 100 mL distilled water. Dilute to reach 300 mL. Store
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precipitate. Materiel needed: Test tubes Rack of test tubes Plastic droppers Beakers Procedure: We prepare 7 beakers of 7 different solutions (that we mark from 1→ 7). We put separately around 50 ml of: HCl NaOH Na2CO3 K2CrO4 CaCl2 CuSO4 Unknown substance Using plastic droppers we mix 10 drops of one solution with 10 drops of another solution in a test tube‚ to get all in all 20 different test tubes. We then note the observation for each test tube. Name of the unknown substance:
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Determining the Percent Copper and Zinc in Pennies from Density Lab Report Procedure: For pre-1982 pennies- Mass 10 pennies‚ record data. Fill a 100mL graduated cylinder to 40mL or enough to fully submerge the pennies with water‚ record the volume in data table. Carefully place the pennies into the graduated cylinder‚ record the final volume of the water in data table. To find the volume of the pennies‚ subtract the final volume from the initial‚ record the data. Repeat this procedure twice more
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