Electrochemistry Pre-Lab Assignment

Electrochemistry Pre-Lab Assignment Purpose Using a voltage probe, the potential of five electrochemical cells will be measured. In Part A, a Cu-Pb voltaic cell will be built with two Pb-”unknown” voltaic cells in Part B which is constructed using a 24-well rest plate, pure metal electrodes and their corresponding metal nitrate solutions. Furthermore, the unknown metals are identities using their measured E° values and the table of standard reduction potentials. In Part C, a copper concentration cell will be constructed from two different concentrations of copper sulfate (CuSO4). In Part D, a lead concentration cell will be constructed from lead nitrate (Pb(NO3)2) and a solution of lead iodide (PbI2). The latter will be a precipitation reaction between the lead nitrate and the potassium iodide. Moreover, the measured potential of the lead concentration cell is then used to calculate the Ksp of the PbI2 using the Nernst equation. Objectives 1. Using a voltage probe, measure 3 voltaic and two concentration cells’ potentials 2. In Part B, identify the unknown “X” and “Y” metals 3. In each anode, determine the anode and cathode of the voltaic cells and then provide the balanced half-reactions and overall net ionic equations 4. With the Nernst equation and calculate the theoretical potential of the copper concentration cell 5. With the Nernst equation determine the Ksp of PbI2 from the potential of the lead concentration cell Compounds Cu(s) electrode Pb(s) electrode “X(s)” electrode “Y(s)” electrode 1 M KNO3 1M CuSO4 0.05 M CuSO4 0.1 M Cu(NO3)2 0.1 M Pb(NO3)2 0.1 M “X(NO3)2” 0.1 M “Y(NO3)2” 0.05 M KI deionized H2O Materials Vernier LabQuest Vernier voltage probe 24-well test plate String (1” pieces) steel wool electrode polishing pad 30 mL beakers (2) glass stirring rod Chemical Hazards Potassium nitrate, copper sulfate, copper nitrate , lead Nitrate, magnesium nitrate, zinc nitrate, and potassium iodide are harmful if touches skin or eyes as they can cause irritation and detrimental if ingested. Physical Hazards Steel wool can cause harm due to loose fibers and can get in eye Sparks from voltage clips can be a fire hazards Broken glassware Outline Part A: Measuring Potential of of a Cu-Pb Voltaic Cell - - Plug lab quest into outlet and turn on Put probe in channel 1 ‘Sensors’ ‘data collection’ ‘Mode’ - ‘selected events’ ‘Name’ should be kept as ‘events’, ‘units’ should be blank Measure the ‘systematic error’ Add KNO3 Assemble Cu-Pb voltaic cell - Add Cu(NO3)2 to A1 - Add Pb(NO3)2 to A2 Polish both sides and place into A1 and A2 Make salt bridge Data collection: - “Collect” - Connect leads from voltage probe so the Cu and Pb potential are positive numbers - Quickly disconnect electrodes - Repeat Part B: Measuring Potential of two Pb-Unknown Voltaic Cells - “X” and “Y” - - - Run 2 Assemble voltaic cell Pb- “X” Add X(NO3)2 to A3 Polish both sides and add it to A2 Polish both sides of “X” and add to A3 Make salt bridge Start collecting data - “Collect” - Connect leads from voltage probe so the Cu and Pb potential are positive numbers - Quickly disconnect electrodes - Repeat Assembled Pb-voltaic cell - Add Y(NO3)2 - Polish Pb and add to A2 - Polish Y(s) and add to B2 - Make salt bridge Collect data - Collect” - Connect leads from voltage probe so the Cu and Pb potential are positive numbers - Quickly disconnect electrodes - Repeat Part C: Measuring Copper Concentration - Assemble copper concentration - CuSO4 in A5 and A6 - Make salt bridge - Collect data Part D - - Prepare Pb(NO3)2 solution Perform reaction between Pb(NO3)2 and KI for the PbI2 solution Run 5 Assemble lead concentration cell - Pb(NO3)2 into D5 - PbI into D6 - Make salt bridge Record data