Forming and Naming Ionic Compounds Lab

Name:_______________________________________ Pd.:______ Forming and Naming Ionic Compounds Lab Problem When do ionic substances react to form a product? What are the names and formulas for these products? Introduction When they dissolve in water, ionic compounds break apart into ions. These ions move about among the water molecules bumping into the other ions and molecules in the solution. When two ionic solutions are mixed several things can happen! In this experiment you will have an opportunity to mix various ionic compounds in solution. When solutions of some ionic compounds are mixed, the cation from one and the anion from another form an insoluble compound which appears as cloudy or grainy solid, called a precipitate. On the other hand, if all cation-anion combinations form soluble pairs, no precipitate appears. All of the ions remain in solution. In this experiment your task will be to mix ions of different kinds and to observe whether they form precipitates. If a precipitate is formed you will write the formula for the new compound and then name the product. Pre-laboratory Assignment 1. Read the Introduction and Procedure before you begin. 2. For the following pairs of ions, write the formula of the compound that you would expect them to form: a. barium and hydroxide b. cobalt(III) and phosphate c. iron(II) and sulfate d. silver and hydrogen carbonate 3. Platinum is a transition metal and forms Pt2+ and Pt4+ ions. Write the formulas for the compounds for each platinum ion with: a. bromide ions b. carbonate ions. c. nitrate ions. Materials Lab apron Safety goggles96-well tray Toothpicks Assorted Solutions Safety 1. Wear safety goggles and lab aprons at all times in the laboratory. 2. No food or drink is allowed in the laboratory at any time. Procedure 1. Obtain a well tray and a paper grid. 2. Obtain a set of the solutions to be tested. These may be in bottles or pipets. It may be helpful to organize these according to their positions on your paper grid. In each box or well place three drops of each solution corresponding to that box. 3. Record in your data/observations table any reaction that occurs or cloudiness that develops. Note both the color and texture of the precipitate (use a toothpick to help determine texture). In those cases where no reaction occurs, mark NR (no reaction) on your data sheet. 4. Continue mixing and recording until your entire data table is complete. Data/Observations K3PO4 PO43− KOH OH− K4Fe(CN)6 Fe(CN)64− K2CO3 CO32− KI I− K2 C2O4 C2O42− Co(NO3)2 Co2+ Pb(NO3)2 Pb2+ CuSO4 Cu2+ Fe(NO3)3 Fe3+ Ni(NO3)2 Ni2+ Sr(NO3)2 Sr2+ AgNO3 Ag+ Cleaning Up 1. Clean the accumulated precipitates and solutions directly from the test plate into the container indicated by your teacher. 2. Thoroughly rinse the test plate. 3. Dispose of all used toothpicks in a waste basket. 4. Wash your hands thoroughly before leaving the laboratory. Analysis and Conclusions 1. For each case in which you found a reaction occurred, write the correct formula for the substance formed. In those cases where no reaction occurred, mark NR (no reaction). K3PO4 PO43− KOH OH− K4Fe(CN)6 Fe(CN)64− K2CO3 CO32− KI I− K2 C2O4 C2O42− Co(NO3)2 Co2+ Pb(NO3)2 Pb2+ CuSO4 Cu2+ Fe(NO3)3 Fe3+ Ni(NO3)2 Ni2+ Sr(NO3)2 Sr2+ AgNO3 Ag+ 2. For each formula write the correct chemical name for the compound formed. In those cases where no reaction occurred, mark NR (no reaction). K3PO4 PO43− Co(NO3)2 Co2+ Pb(NO3)2 Pb2+ CuSO4 Cu2+ Fe(NO3)3 Fe3+ Ni(NO3)2 Ni2+ Sr(NO3)2 Sr2+ AgNO3 Ag+ KOH OH− K4Fe(CN)6 Fe(CN)64− K2CO3 CO32− KI I− K2 C2O4 C2O42− Experiment 15 Forming and Naming IIonic onic Compounds Introduction Intent This experiment provides students with visual examples of many, many ionic compounds, and the opportunity to see the precipitates form in small-size samples. The mixing is done directly on a sheet of acetate, which is placed over a preprinted grid. The solutions are distributed to the students in small plastic bottles. The simple procedure and the colorful outcomes make formula-writing more directly connected to real chemical reactions. Objectives 1. To perform reactions mixing ionic solutions together. 2. To practice writing formulas for the compounds that form when the solutions are mixed. Materials (for each lab team of 2 students) Appar Apparatus atus      Lab apron (2) Safety goggles (2) 96-well tray or acetate sheet Toothpicks Paper grid Reagent solutions            Sodium phosphate Potassium hydroxide Sodium oxalate Cobalt chloride Strontium chloride Potassium ferrocyanide Sodium carbonate Silver nitrate Copper(II) sulfate Nickel(II) chloride Potassium iodide   Lead(II) nitrate Iron (III) nitrate Prepar Preparation ation Hints 1. Very small quantities of the solutions are used. If you prepare about 1000 mL of each solution, and distribute each in small plastic bottles, the solutions can be kept from year to year and simply replenished as needed. 2. Concentration of all solutions are 0.2 are as follows: M. Directions for the preparation of the solutions Potassium hydroxide (KOH, 11.2 grams/liter) Sodium oxalate (Na2C2O4, 26.8 grams/liter) Cobalt chloride (CoCl2 · 6H2O, 47.6 grams/liter) Potassium permanganate (KMnO4, 31.6 grams/liter) Potassium ferrocyanide (K4Fe(CN)6 · 3H2O, 84.5 grams/liter) Nickel(II) chloride (NiCl2 · 6H2O, 47.5 grams/liter) Sodium carbonate (Na2CO3, 21.2 grams/liter) Potassium iodide (KI, 33.2 grams/liter) Sodium sulfide (Na2S · 9H2O, 48.0 grams/liter) Lead(II) nitrate (Pb(NO3)2, 66.2 grams/liter) Copper(II) sulfate (CuSO4 · 5H2O, 49.9 grams/liter) Iron (III) nitrate (Fe(NO3)3 · 9H2O, 80.8 grams/liter) Silver nitrate (AgNO3, 34.0 grams/liter) Strontium chloride (SrCl2 · 6 H2O, 71.1 grams/liter) Sodium phosphate (Na3PO4 · 12H2O, 76.0 grams/liter) 3. Many different ionic solutions can be effectively used in this experiment. Student interest is heightened when the reactions produce colorful, interesting precipitates. 4. Suggestions for solutions with reactive positive ions include: Ba(NO3)2, Fe(NO3)3, NiCl2, Al(NO3)3, Pb(NO3)2, AgNO3, CoCl2, CuSO4, Ca(NO3)2, Sr(NO3)2, MnCl2 5. Suggestions for solutions with reactive negative ions include: Na2SO4, Na2CO3, K4Fe(CN)6, NaOH, Na3PO4, NaCl, KI, NaBr, Na2SO3 6. Distribute the bottles labeled with the entire formula on them, such as: AgNO3, Na3PO4. Since this lab is an introduction to writing formulas, the key positive or negative ions are listed on the table in the Report Sheet. Prelab Discussion This experiment requires little or no prelab discussion. Students are given the opportunity to see many different chemical reactions in a short period of time. The text gives formulas for all ions except ferrocyanide. As part of the prelab, put the formula for potassium ferrocyanide on the board. Have students reason out, perhaps using the flow chart in Figure 4.2, what the formula and charge of ferrocyanide must be: Fe(CN)64–. Procedure Hints 1. Some students will find the use of toothpicks helpful to test the actual texture of the precipitates. 2. The acetate sheets or well trays make clean-up very easy. Caution students to use small quantities of solutions on the acetate sheets so that the precipitates do not run together. Disposal All precipitates should be cleaned off the plastic sheets or out of the well trays with paper towels and disposed of in solid waste containers. Supply cotton swabs for cleaning stubborn precipitates from test plate wells. Postlab Discussion Some students will be uncertain as to whether or not an actual reaction has occurred during the experiment. Some of the precipitates are quite indistinct, thus the results may vary. Name___________________________ Report for Experiment 15 Section___________ Date___________ Prelabor Prelaboratory atory Questions 1. For the following pairs of ions, write the formula of the compound that you would expect them to form: a. barium and hydroxide b. cobalt(III) and phosphate c. iron(II) and sulfate d. silver and hydrogen carbonate Ba(OH)2 CoPO4 FeSO4 AgHCO3 2. Platinum is a transition metal and forms Pt2+ and Pt4+ ions. Write the formulas for the compounds for each of these ions with a. bromide ions PtBr2, PtBr4 b. carbonate ions PtCO3, Pt(CO3)2 Data/Observ Data/Observations ations All colors listed indicate precipitates Na3PO4 PO43− KOH OH− K4Fe(CN)6 Fe(CN)64− KI I− Pink/purple None Na2 C2O4 C2O42− CoCl2 Co2+ Pink Cloudy blue green Pb(NO3)2 Pb2+ White White White White Bright yellow White CuSO4 Cu2+ Light blue Light blue Brown Light blue Light brown None Fe(NO3)3 Fe3+ Yellow brown Yellow brown Dark blue Brown NiCl2 Ni2+ Light green Light green Light green Pale yellow green None None SrCl2 Sr2+ White Cloudy white None White None White AgNO3 Ag+ Yellow brown Brown White White Pale yellow White Analysis and Conclusio Conclusions ns Green Na2CO3 CO32− None None None 1. For each case in which you found a reaction occurred, write the correct formula for the substance formed. Na3PO4 PO43− KOH OH− K4Fe(CN)6 Fe(CN)64− Na2CO3 CO32− KI I− Na2 C2O4 C2O42− CoCl2 Co2+ Co3(PO4)2 Co(OH)2 Co2Fe(CN)6 CoCO3 --- --- Pb(NO3)2 Pb2+ Pb3(PO4)2 Pb(OH)2 Pb2Fe(CN)6 CuSO4 Cu2+ Cu3(PO4)2 Cu(OH)2 Cu2Fe(CN)6 CuCO3 CuI2 --- Fe(NO3)3 Fe3+ FePO4 Fe(OH)3 Fe4(Fe(CN)6)3 Fe2 (CO3)3 --- --- NiCl2 Ni2+ Ni3(PO4)2 Ni(OH)2 Ni2Fe(CN)6 NiCO3 --- SrCl2 Sr2+ Sr3(PO4)2 Sr(OH)2 --- AgNO3 Ag+ Ag3(PO4)2 AgOH Ag4Fe(CN)6 PbCO3 PbI2 SrCO3 --- Ag2CO3 AgI PbC2O4 --SrC2O4 Ag2C2O4 Note: The phosphate and carbonate anions react with water to produce basic solutions. Therefore the precipitates with these anions are often hydroxides rather than the expected compound. At this point in the course the students would have no way of knowing this so we supplied the formula for the compound the student should expect. 2. For each formula write the correct chemical name for the compound formed. Column 1: cobalt(II) phosphate, lead(II) phosphate, copper(II) phosphate, iron(III) phosphate, nickel(II) phosphate, strontium phosphate, silver phosphate Column 2: cobalt(II) hydroxide, lead(II) hydroxide, copper(II) hydroxide, iron(III) hydroxide, strontium hydroxide, silver hydroxide Column 3: cobalt(II) ferrocyanide, lead(II) ferrocyanide, copper(II) ferrocyanide, iron(III) ferrocyanide, nickel(II) ferrocyanide, silver ferrocyanide Column 4: cobalt(II) carbonate, lead(II) carbonate, copper(II) carbonate, iron(III) carbonate, nickel(II) carbonate, strontium carbonate, silver carbonate Column 5: lead(II) iodide, copper(II) iodide, silver iodide Column 6: lead(II) oxalate, strontium oxalate, silver oxalate