Galvanic Cells
Introduction:
The goal of the experiment was to measure the voltage of cells with known concentrations. The Nernst Equation: Ecell = Eo - .0592/n ; was useed to calculate unknown concentrations from the measured voltages and observed polarities of galvanic cells. The concentrations were then used to calculate the values of the equilibrium constants for the formation of tetraammineezinc ion, and the dissolving silver chloride. The experiment was divided into five parts. Each part contained a discussion of the theory and calculations, which corresponds to the construction of the galvanic cell. The equation used for part D was:
Kf=[Zn(NH3)2+] / [Zn2+] [NH4]4
The equation used in part E was: Ksp = [Ag+] [Cl-]
Procedure:
Part A- A vial was filled half way with a 0.2M ammonium nitrate solution, and clamped onto a ring stand. A small wad of cotton was packed tightly into the bottom of a medicine dropper. The dropper was filled two-thirds of the way with 0.1M copper (II) sulfate. The dropper was placed into the ammonium nitrate solution, and a bit more copper (II) sulfate solution was added. A piece of copper was added to the dropper. A half cell containing 0.1M Silver Nitrate and a wire of silver medal was prepare vial with the copper electrode. The voltmeter leads were attached to the copper and sliver electrodes so there as a positive reading. The initial Ecell was recorded along with the polarity. The half-cell reactions and the equation for the spontaneous cell reaction were written. Finally, the Nernst Equation was used to calculate the Eo for the cell.
Part B- The silver half-cell was replaced by a zinc half-cell. The half-cell was prepared from a dropper, wad of cotton, 0.1M zinc sulfate, and a zinc strip. The voltmeter leads were attached in order to get a positive reading. The Ecell and the polarity were measured and recorded. The half cell reactions and the equation for the spontaeous cell reaction were written. The Eo for the cell was calculated.
Part C -- The copper and silver half cells were exchanged and the liquid levels were adjusted. The Ecell and polarity were measured and recorded. The half-cell reactions and the equation were written. The Eo was also calculated.
Part D- Part D started by mixing in a clean vial, twenty drops of 0.1M zinc sulfate with twenty drops of 6M ammonia. A half-cell was prepared from the solution, a dropper, a wad of cotton, and zinc strip.
The pump exchanges three sodium molecules for two potassium molecules. In doing so an electrical gradient is formed across the basolateral membrane of the cell due to the imbalance of charge generated. The interior of the cell is negative by about 80mV in relation to the outside...
- The area should be kept dry and taps should be switched off. Variables: I will only be changing the current by moving the variable resistor. I will repeat the experiment twice so that I can be sure of my readings and see if anything has changed or gone wrong. I will take 12 readings at 0.1 amps intervals. Apparatus: o Voltmeter o Ammeter o Variable resistor o 12 volt lamp o Battery pack (set at 12 volts ) o Leads Method: 1.
In the first part of this project, two cation elimination tests and one cation confirmation test were performed. 10 drops of 4 cation solutions: potassium, zinc(II), copper(II)
Volume's Effect on a Copper Sulphate Solution We are trying to find out if the current though a copper sulphate solutions volume is increased. To find this information out I shall perform an experiment using the following equipment; · 1 power pack · 1 beaker · 2 carbon rods for anode and cathode · 1 ammeter · 1 measuring cylinder · 2 crocodile clip wirers I shall also be using 60cm3 volume of copper sulphate in my preliminary results to decide upon the concentration of copper sulphate and the voltage I shall use. The following diagrams show the step by step process in which I will do my experiment; [IMAGE] [IMAGE] [IMAGE] [IMAGE] I will take 10 readings from 10cm3 to 100cm3. I will repeat my experiment to give my experiment a fair average. I will keep the power pack the beaker the carbon rods the crocodile clips the ammeter the concentration of copper sulphate and the measuring cylinder the same each time I do the experiment this experiment.
The purpose of this experiment is to determine the molarity of a permanganate solution through the use of redox titration.
Results and Discussion A film of COOH-functionalized nanotube suspense was dried on the working electrode of the SPE. Experiments were performed at the physiological pH of 7.4 because at this pH both the carboxyl group of the nanotubes and a hydroxyl group of ascorbic acid would be largely deprotonated.7 It was expected that the repulsion of like charges would prevent ascorbic acid from reaching the working electrode, and therefore would prevent the ascorbic acid from taking part in a redox reaction. While the application of the nanotube suspension reduced the effect of ascorbic acid at higher potentials in cyclic square wave voltammetry, it also resulted in the occurrence of a split anodic peak for the ascorbic acid at a potential near
The Nernst equation line in Figure 1 shows only how the change in extracellular potassium concentration can lead to a change in membrane voltage. Therefore, the other lines may be a reflection of the effects of chloride extracellular concentration changes. It is important to realize that these changes in chloride concentration also affected chloride’s reversal potential; increases in chloride’s concentration also lead to an increase in chloride’s reversal potential. Given the membrane’s slight permeability to chloride, the ion was able to more easily than other ions travel down its chemical gradient and into the cell. In the areas of the graph where the experimentally derived data points were significantly depolarized relative to the Nernst values, the chloride ion may have had a lowered driving force, given that the pipet did have a minute amount of chlorine in it that entered the intracellular environment.
The procedure for this experiment can be found in Inorganic Chemistry Lab Manual prepared by Dr. Virgil Payne.
Another widely used primary cell is the zinc-mercuric-oxide cell, more commonly called a mercury battery. It can be made in the shape of a small flat disk and is used in this form in hearing aids, and electric wristwatches. The negative electrode consists of zinc, the positive electrode is of mercuric oxide, and the electrolyte is a solution of potassium hydroxide. The mercury battery produces about 1.34 volts.
In the first part of the experiment, The mixture was combined with saturated sodium chloride, and the aqueous layer, containing alcohol, some acid, and water, was discarded. The organic layer was then dried with granular anhydrous sodium sulfate; this drying agent is used to absorb any water in a solution and should thus, result in a colorless solution. The final product was collected; it was mostly clear, though it has a pale yellow tint. Data Table 2 shows the results and calculations that were gathered after the completion of this experiment. No errors had occurred during the course of the experiment, which is testified by the fairly, high yield of Data Table 3 indicates the observations from these tests.
== § Test tubes X 11 § 0.10 molar dm -3 Copper (II) Sulphate solution § distilled water § egg albumen from 3 eggs. § Syringe X 12 § colorimeter § tripod § 100ml beaker § Bunsen burner § test tube holder § safety glasses § gloves § test tube pen § test tube method = == = =
...ations served as background information for the calculations and for the general procedure of the lab. The solid acid, when added to water ionized to form charged particles causing the solution to have a certain pH that could be figured out from a titration curve graph. The acid used in this lab, KHP, ionized in water and formed Hydronium ions in the water. These ionized particles were what gave the acid a certain pH and those particles were what was being neutralized in the reaction. Multiple titrations were performed to neutralize the acid, in each titration, the lab groups attempted to reach the exact endpoint of the reaction without going over it. The endpoint was indicated by a slight color change in the solution to a pale pink color. When the endpoint was achieved, the calculations for the moles of acid to the moles of base were equal at that point.
In the experiment there are several possible ways of changing the electric current such as changing the voltage or the position of the electrodes within the electrolysis cell. However, it was found from preliminary work that the most effective way to change the current was to change the concentration of the acid solution. The preliminary work showed that the greater the concentration of the acid, the greater the current. Ohm's law states that R(resistance) =
Chemistry: Acid-Base Titration. Purpose: The objective of this experiment were: a) to review the concept of simple acid-base reactions; b) to review the stoichiometric calculations involved in chemical reactions; c) to review the basic lab procedure of titration and introduce the student to the concept of a primary standard and the process of standardization; d) to review the calculations involving chemical solutions; e) to help the student improve his/her lab technique Theory: Titration was used to study acid-base neutralization reaction quantitatively. In acid-base titration experiment, a solution of accurately KHP concentration was added gradually to another solution of NaOH concentration until the chemical reaction between the two solutions was completed. The equivalence point was the point at which the acid was completely reacted with or neutralized by the base.
In this experiment three different equations were used and they are the Stoichiometry of Titration Reaction, Converting mL to L, and Calculating the Molarity of NaOH and HCl (Lab Guide pg. 142 and 143).