Please an.swer questions 1-5, Given data in the last image. Lots of backround information given for reference. Thank you

Q1: Write out the chemical equation for the redox reaction that was under study in this lab and use it to calculate Q. Note: Do not worry about activities. Then, using Q and Equation

[5], find the value of Ecell 80 at each temperature point.

Q2: Crea.te a plot of Ecell versus temperature.

Q3: Using the line of best fit, interpolate what the value of Ecell should be at T = 298 K. This will be known as E298. Compare the calculated value with the literature value.

Q4: Using the value isolated for E298, calculate ?rG?.

Q5: Using the plot composed in Step C2, determine ?rS?for this reaction. Then, using the

value of ?rG? calculated earlier, find ?rH?.

Experiment 4- Thermodynamic factions of a Galvanic Cell EXPERIMENT 4 Thermodynamic Functions of a Galvanic Cell Introduction Chemical Reactions Involving the Transfer of Electrons Numerous chemical reactions have been studied which involve the transfer of electrons from one species to another. The chemical species which has donated electrons is defined as the reducing agent and is said to have undergone the process of oxidation over the course of the reaction. The chemical species which receives the electrons is defined as the oxidizing agent and is said to have undergone the process of reduction over the course of the reaction. A redox (reduction/oxidization ) reaction is the term applied to a reaction in which electrons are transferred from one chemical species to another. Half-Reactions Although the processes of oxidation and reduction occur simultaneously, the technique most widely used for understanding redox reactions involves separating them into half-reactions. This separation can be done in more than one equivalent fashion, with one way being outlined below. Consider the redox reaction where tin(II) and iron(Ill) are the reagents: Sn 2+ + 2F 03+ Sn 4+ + 2F0 2+ (aq) (aq) (aq) (aq) Above is the net ionic equation describing this redox reaction in aqueous media; below, the same redox reaction is expressed as two reduction half-reactions: (A) 2F3+ 2FO 2+ + 20 (aq) (aq) 121 (B) Sn4+ Sp 2+ + 20 (aq) (aq) By taking the difference between the two half-reactions in Equations [2], one can arrive at [1]. The Electrochemical Cell The separation of redox reactions into half-reactions is convenient, and it reminds one of the electrochemical cell, a common physical construct used when studying this type of reaction. Each physical half-cell is composed of a single electrode, which is placed in contact with an electrolyte of some sort. A typical half-cell will have a strip of metal, M, (the electrode) which is in contact with an aqueous solution that contains ions of this metal (the electrolyte), Mo, where n is the charge number associated with a particular oxidation state of the metal. A low resistancewire will allow the passage of electrons from one electrode to the other. Note that there are many variations to this scheme, one of which will be utilized in this experiment. The fashion in which the cell circuit is completed also varies, but one regularly used method involves a salt bridge, and it is the method that will be used for this experiment. A salt bridge is often made by adding agar to an electrolytic solution followed by heating. Upon cooling, the solution will turn into a gel. A connected set of two half-cells is called an electrochemical cell; a general schematic of which is provided below: Switch Voltmeter 1. 10 Zn anode NOT NJ Cu cathode NO. NO Zn - Zn2+ jani + 20 Movement of cations Movement of anions Figure 4.1 Once connected, a redox reaction may begin to occur spontaneously, accompanied with the production of electricity. In cases of this sort, the electrochemical cell is referred to as a galvanic cell. If electricity is required to drive the chemical reaction, the redox reaction being considered is non-spontaneous and the electrochemical cell is known as an electrolytic cell. Regardless of the type of electrochemical cell, the flow of electrons is from the anode (this is the electrode at which the process of oxidation occurs) to the cathode (the electrode at which reduction occurs). Gibbs Energy Change and the Cell Potential In galvanic cells, as with any spontaneous process, the redox reaction occurs spontaneously due to the fact that the chemical potential, , of the system decreases. If the system is under constant temperature and pressure conditions, the chemical potential change of the system can be related in a straightforward fashion to the Gibbs energy change, AG. Additionally, as long as the process is reversible, AG can be related to the cell potential, Es, (or the electromotive force, (emf)) which is defined as being the electrical potential difference between the anode and cathode and is related to the maximum amount of electrical work, Wemax, that can be done by the system. The above statements are represented algebraically: "B - HA = AIG = W e, max = -IF E 131 cell Where B is some final state, A is some initial state, Ecg is in units of V mol ', v is the number of electrons transferred (units of mol), and F is the Faraday constant (96 485 C mol').Experiment 4 - Thermodynamic Functions of a Galvanic Cell Eall as a function of Cell Composition The relationship between the reaction quotient, Q, and the Gibbs energy of reaction takes on the form below: AG = AG' + RTInQ HI where A G" is the change in Gibbs energy when the system is under standard conditions. The above equation can be re-expressed using Equation [3]: Ecel = E cep Boys - RT - InQ 151 The form above is known as the Nemst equation and Eca 80 is defined as the standard omf. Other Thermodynamic Functions It has been established that the emf is related directly to the Gibbs energy of reaction, but the fashion in which the emf varies with respect to temperature can allow one to determine the change in another thermodynamic function of state. By taking the derivative of the isolated Eca value with respect to temperature, the entropy of reaction, AS, can be determined: de cell AS 16] dT VF Once the values for A S and AG are known, the enthalpy of reaction, A,H, for the particular redox reaction may be determined. Glassware and apparatus: 4 - 100 mL beakers scissors 2 - 100 mL beaker lids 2 - stir bars 1 - glass funnel 2 - stir rods 1 - 10 mL graduated cylinder 2 - 50 mL volumetric flasks 2 -50 mL graduated cylinders 1 - water bath (glass) plastic tubing Instruments and equipment: Electrodes: 1 - platinum and 1 - zinc Sandpaper Hot plate stirrerswith temperature probe Voltmeter 1 MQ Resistor Chemicals agar potassium ferricyanide (K Fe(CN).) PH 4 buffer potassium nitrate (KNO.) . potassium ferrocyanide zinc chloride (ZnClz) (K.Fe(CN)-3H20)Experiment 4- Thermodynamic Functions of a Galvanic Cell Procedure Perform all pre-laboratory calculations (indicated by the icon ) prior to coming to the lab. Review the calculations with the GA before preparing the solutions. Part A: Preparation of the Salt Bridge (another group member should start on Part B) 1 . Measure 50 mL of deionized water into a graduated cylinder. 2 Using a weigh boat, weigh out enough KNO, to make a 0.1 M solution. Transfer to a clean 100 mL beaker. Rinse the weigh boat with a small amount of the pre-measured deionized water and transfer the rinsing to the beaker. 3. Weigh out 2 grams of agar into another weigh boat and transfer to the same 100 mL beaker. Rinse the weigh boat with the remaining deionized water and transfer the rinsing to the beaker. 4 He at this solution with stirring to around 85 "C. To do this, turn the heating function of the hot plate on, and set the dial to around 150 "C. On the temperature probe (or thermocouple) display, set the temperature to 95 "C (note that this is about 10 *C above the target temperature). The probe is designed such that the solution may be heated by the hot plate to a range of desired temperatures. Wait until the solution is clear and bubbles have started to form. 5 While the solution is heating, measure and cut the length of the tubing needed to prepare the salt bridges to -15 cm. A minimum of five salt bridges will be needed. 6. Remove the beaker from the heat, then using a Pasteur pipet attached to one end of the tubing, squeeze the pipet bulb to draw a portion of the hot solution into the tubing until the entire tube is filled with agar solution. Remove the pipet and allow to cool Once this cools (allow approximately 20 - 30 min), it will form a gel and may be used as the salt bridge. Repeat this procedure until a minimum of five salt bridges are prepared. Note: Dispose of any remaining agar in the solid waste container provided. Part B: Preparation of Required Solutions The reagents will be weighed in weigh boats and transferred to 50 mL volumetric flasks. Ensure all the contents of the weigh boats are transferred to the flasks by rinsing the weigh boats and then transferring the rinsing to their respective volumetric flasks. Ensure all the contents in the flasks are dissolved before completing the volume to 50 mL. Prepare the following solutions using deionized water (do not use tap water): 1 . 50 mL of a solution that is 0.10 M in BOTH potassium ferrocyanide (K Fe(CN)-3HO) and potassium ferricyanide (K Fe(CN) ). Transfer the solution to a clean 100 mL beaker.of a Galvanic Cell 2. 50 mL of 0.15 M zinc chloride (ZnCl:) solution. Dissolve initially in 10 mL of pH 4 buffer in a 50 mL volumetric flask before completing the volume with deionized water. Transfer the solution to a second clean 100 mL beaker. Part C: Effect of Temperature on Esau Note: Seek the assistance of the GA to set-up the voltmeter, leads, and electrodes. 1 . Create an ice slurry using the water bath as a container and then assemble the electrochemical cell as shown in Figure 4.2. Add a stir bar to the bath as well. temperature probe resistor/voltmeter Zn electrode connection Pt electrode connection 100 mL beaker w Zn* 100 mL beaker w Fe(CN):3-4 hot plate/stirrer Figure 4.2 2. When ready, turn the heating/stirring functions on and set the temperature to around 175 "C. On the temperature probe display, set the temperature to 20 *C. 3. As the temperature gets close to the desired value (~ 1 *C away), cut the ends of the salt bridge so that the gel runs the full length of the tubing and add to the beakers. Ensure the voltmeter is set to read direct current (or DC voltage), V . When the temperature on the temperature probe reaches at 10 *C, record the cell potential on the voltmeter in the Data Sheet. The temperature will continue to increase until the set temperature on the temperature probe. 5 Once the reading has been made, disconnect the circuit by removing one of the leads connected to an electrode and heat the system to 15 *C. 6. Continue taking measurements and heating the system until the Data Sheetis completed.EXPERIMENT 4 Thermodynamic Functions of a Galvanic Cell Part B: Preparation of Required Solutions Mass of ZnClz solution: 1.022 g Part C: Effect of Temperature on Ecar Temperature Ecell ("C) (V mol-1) 10 1.183 15 1.178 20 1.170 25 1.161 30 1.149 35 1.143 40 1.136 45 1.128 50 1.118