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MAKING COPPER: STOICHIOMETRY – I

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MAKING COPPER: STOICHIOMETRY – I Revised: 8/10/10 Chemistry 40 – Fall 2010 Page 1 of 8 PRE-LAB ACTIVITIES/QUESTIONS Instructions: Complete the following pre-lab activities/questions before coming to lab. The instructor will check the pages for completion at the beginning of the lab. 1. ___ I have read the Introduction to the experiment and provided my answers to all embedded questions in the spaces provided in the Introduction. 2. ___ I have watched the pre-laboratory video clip on Stoichiometry and answered all questions. See attached sheet(s) at the end of this document. Name:__________________________MAKING COPPER: STOICHIOMETRY – I Revised: 8/10/10 Chemistry 40 – Fall 2010 Page 2 of 8 OBJECTIVE Part 1: The purpose of this experiment is to verify the mass-mole relationship among reactants and products and determine percent yield of the reaction product. INTRODUCTION Stoichiometry deals with quantities and chemical reactions. You should be able to the following in order to perform stoichiometric calculations: 1) Convert between a given substance’s mass to mole (and vise versa) quantities. 2) Classify a reaction and predict reaction products. 3) Balance chemical reactions. 4) Use balanced coefficients in order to calculate any mole or mass quantity. 5) Distinguish between excess and limiting reactants. Review the above concepts from your textbook. SAFETY/LAB TECHNIQUES Wear safety goggles at all times. 1) Review all safety rules and be conscious of the environment around you. If you find someone violating any safety rules, talk to your instructor. 2) Keep your work area clean, free from spilled chemicals and scattered paper towels. 3) Dispose of all chemical waste into properly labeled waste containers. Be sure that you are clear about chemicals that can be safely disposed down the sink and those that should be properly collected as waste. 4) Don’t take any more chemicals than you need for an experiment and never return the unused chemical back into the original container. Unused chemicals should be properly discarded. 5) Work with a partner only if authorized by your instructor. Otherwise you are expected to work individually. 6) Read the introduction to an experiment before coming to the lab. It will take you less time and you are less likely to make mistakes if you review the introduction and experimental steps before actually doing them. 7) Learn to work with your lab equipment and always record any measurement to the maximum precision of any laboratory equipment. 8) Review the rules of Significant Figures and follow the rules in each calculation step. Carry an extra digit and place a bar over it, in order to keep track of SF and avoid any round off errors.MAKING COPPER: STOICHIOMETRY – I Revised: 8/10/10 Chemistry 40 – Fall 2010 Page 3 of 8 MATERIALS AND EQUIPMENT Solids Liquids Equipment/Glassware CuCl2.2H2O (s) Aluminum foil HCl, 3 M Centigram scale (shared) Hot plate (shared) 100-mL beaker (1/student) 10-mL graduated cylinder (1/student) 50-mL graduated cylinder (1/student) Watch glass (1/student) Wash bottle (1/student) Evaporating dish (1/student) Metal spatula (1/student) WASTE DISPOSAL All waste should be disposed in properly labeled waste containers. Solid metals should be separated from the liquid waste and disposed in a separate container.MAKING COPPER: STOICHIOMETRY – I Revised: 8/10/10 Chemistry 40 – Fall 2010 Page 4 of 8 EXPERIMENTAL PROCEDURES AND PROBLEM SOLVING General lab instructions: - Solve the problems following each short experiment before performing the next step. - Provide the answers to the problems on the spaces provided. - You are expected to work individually on all parts of this experiment and solve the problems on your own. If you have difficulty with any of the problems, talk to your instructor. - All lab data should be recorded in pen. All calculations should be in pencil. Lab data should not be recorded in a way to be erased or obliterated. If you have to correct a lab data, draw a line over the old data and write the corrected value above it. Calculations should always be in pencil so that you can erase and correct your mistakes keeping your work neat and organized. - Read every numbered procedure first and record the data in the spaces provided. - Record every measurement to the highest precision of the measuring device. Be sure that your reported values include units. - Unless stated otherwise water refers to pure water and not “tap” water. Find the location of pure water faucets in your laboratory. These faucets may be labeled as “DI” water. DI water is a water purified or “deionized” to serve as pure water. - Express all reported values to proper number of significant figures. - Never return unused solid powder or liquids back to the original chemical container. Discard unused chemicals in a properly labeled waste container. Part IA: A Single Replacement Reaction We will study the reaction of copper(II) chloride, CuCl2 with aluminum (foil) metal. The copper(II) chloride salt is a “hydrated” salt which means that it contains water. Water is not visible and is “locked” within the solid in an exact ratio given by the formula CuCl2.2H2O. The formula implies that every mole of CuCl2 contains 2 moles of water. You should calculate the molar mass of the hydrated salt by adding the total mass of two water molecules to the mass of CuCl2. When the hydrated salt is dissolved in water, the balanced solubility reaction is; CuCl2.2H2O (s) → CuCl2 (aq) + 2H2O (l) Reaction 1 Hydrated salt Next we will react the CuCl2 with Aluminum (foil). The unbalanced reaction is: CuCl2 (aq) + Al → Cu (s) + AlCl3 (aq) Reaction 2 Classify, balance and write total ionic and net ionic equations for Reaction 2: Reaction Type: Total ionic: Net ionic: Practice problem (check your answers with your instructor before proceeding to the next page): A student weighs 1.93 g of the hydrated salt and dissolves it in some water.MAKING COPPER: STOICHIOMETRY – I Revised: 8/10/10 Chemistry 40 – Fall 2010 Page 5 of 8 a) Calculate molar mass of the hydrated salt. Molar mass:___________ b) Calculate moles of dissolved copper(II) chloride, CuCl2 (aq). mol of CuCl2:_________ c) Calculate the minimum mass of aluminum metal needed for the reaction: mass


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