Teacher Notes
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Teacher Notes![]() Mole RatiosStudent Laboratory KitMaterials Included In Kit
Acetone, 250 mL*
Copper wire, Cu, 18-gauge, 15 ft (457 cm) Nitric acid, HNO3, 3 M, 10 mL† Silver nitrate, AgNO3, 25 g Wooden splints, 15 *Two rinse beakers with 125 mL of acetone should be shared. Place in the hood or a central location. †In a dropper bottle for safety and ease of use. Additional Materials Required
(for each lab group)
Water, distilled or deionized Balance, centigram (0.01-g precision), 3 Beaker, 50-mL, 15 Beaker, 100-mL, 15 Beakers, 250-mL, 2 Erlenmeyer flasks, 125-mL, 15 Labeling or marking pens, 3 Spatulas, 15 Stirring rods, 15 Wash bottles, 15 Wire cutters Safety PrecautionsNitric acid is a corrosive liquid and a strong oxidizer. Silver nitrate is a corrosive solid and is toxic by ingestion; it will stain skin and clothes. Acetone is a flammable liquid; avoid contact with flames and other sources of ignition. Avoid contact of all chemicals with eyes, skin and clothing. Wear chemical splash goggles and chemical-resistant gloves and apron. Remind students to wash hands thoroughly with soap and water before leaving the laboratory. Please consult current Safety Data Sheets for additional safety, handling and disposal information. DisposalPlease consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The solution remaining after the silver-clad copper wire has been removed contains excess silver nitrate and should be disposed of by precipitating silver chloride, according to Flinn Suggested Disposal Method #11. The aqueous rinse solution may be flushed down the drain with excess water according to Flinn Suggested Disposal Method #26b. Acetone may be allowed to evaporate in the hood according to Flinn Suggested Disposal Method #18a. Leftover silver metal and copper wire may be disposed of in the solid waste according to Flinn Suggested Disposal Method #26a. Many teachers allow their students to keep their silver in a small vial as a souvenir. It is also possible to recycle the silver: collect the silver, place it in a hollow formed in a block of charcoal, and fuse it into a little silver nugget using a mini torch. Lab Hints
Teacher Tips
Further ExtensionsSupplementary Information {13867_Extensions_Table_2}
Sample Results The results of all calculations have been rounded to the appropriate number of significant figures. {13867_Extensions_Table_3}
Procedure
Correlation to Next Generation Science Standards (NGSS)†Science & Engineering PracticesPlanning and carrying out investigationsAnalyzing and interpreting data Using mathematics and computational thinking Disciplinary Core IdeasHS-PS1.B: Chemical ReactionsCrosscutting ConceptsScale, proportion, and quantityEnergy and matter Performance ExpectationsHS-PS1-6: Refine the design of a chemical system by specifying a change in conditions that would produce increased amounts of products at equilibrium. Answers to Prelab QuestionsCopper(II) chloride (CuCl2; 0.98 g) was dissolved in water and a piece of aluminum wire (Al; 0.56 g) was placed in the solution. The blue color due to copper(II) chloride soon faded and a red precipitate of solid copper was observed. After the blue color had disappeared completely, the leftover aluminum wire was removed from the solution and weighed. The mass of the leftover aluminum wire was 0.43 g.
Sample Data{13867_Data_Table_1}
Answers to Questions
ReferencesThis activity is from Flinn ChemTopic™ Labs, Volume 7, Molar Relationships and Stoichiometry; Cesa, I., Ed., Flinn Scientific: Batavia, IL, 2002. |
Student Pages
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Student Pages![]() Mole RatiosIntroductionThe reaction of copper wire with silver nitrate in aqueous solution shows chemistry in action—delicate silver crystals grow on the wire surface and the color of copper(II) ions gradually appears in solution. What relationships govern the relative quantities of reactants and products in this chemical reaction? Concepts
BackgroundStoichiometry is the branch of chemistry that deals with the numerical relationships and mathematical proportions of reactants and products in a chemical reaction. One of the most important lessons of stoichiometry is that the amounts of the reactants and products in a chemical reaction are related to one another on a mole basis. Chemical reactions are normally represented by balanced chemical equations. The coefficients in a balanced chemical equation summarize the relative number of moles of each reactant and product involved in the reaction. The ratios of these coefficients represent the mole ratios that govern the disappearance of reactants and appearance of products. Knowing the mole ratios in a balanced chemical equation is essential to solving stoichiometry problems. a Cu(s) + b AgNO3(aq) → c Cu(NO3)2(aq) + d Ag(s) The values of the coefficients a, b, c and d can be determined experimentally by measuring the mass of copper wire that reacts and the mass of metallic silver that is produced in the above reaction.Experiment OverviewThe purpose of this experiment is to determine the number of moles of reactants and products in the reaction of copper and silver nitrate and calculate their mole ratio. The mole ratio relating the disappearance of copper and the formation of silver metal will be used to write the balanced chemical equation for the reaction. Materials
Acetone, CH3COCH3, 125-mL, in a 250-mL beaker*
Copper wire, Cu, 25 cm Nitric acid, HNO3, 3 M, 3 drops Silver nitrate, AgNO3, 1.5 g Water, distilled or deionized Balance, centigram (0.01-g precision) Beakers, 50- and 100-mL Labeling or marking pen Erlenmeyer flask, 125-mL Spatula Stirring rod Wash bottle Wooden splint *This acetone rinse beaker (shared) will be in a safe location determined by instructor. Prelab QuestionsCopper(II) chloride (CuCl2; 0.98 g) was dissolved in water and a piece of aluminum wire (Al; 0.56 g) was placed in the solution. The blue color due to copper(II) chloride soon faded and a red precipitate of solid copper was observed. After the blue color had disappeared completely, the leftover aluminum wire was removed from the solution and weighed. The mass of the leftover aluminum wire was 0.43 g.
Safety PrecautionsNitric acid is a corrosive liquid and a strong oxidizer. Silver nitrate is a corrosive solid and is toxic by ingestion; it will stain skin and clothes. Acetone is a flammable liquid; avoid contact with flames and other sources of ignition. Avoid contact of all chemicals with eyes, skin and clothing. Wear chemical splash goggles and chemical-resistant gloves and apron. Wash hands thoroughly with soap and water before leaving the laboratory. Procedure
Student Worksheet PDF |