EXPERIMENTAL Part A obtain four 50 mL beakers and label them ZnONOh)2.1M cuso. o
ID: 497407 • Letter: E
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EXPERIMENTAL Part A obtain four 50 mL beakers and label them ZnONOh)2.1M cuso. o.1 M cusou and Feso, respectively. Using a clean graduated cylinder, transfer 30 ml of 1 M znONOh)2 solution into the beaker labelled zn (NO) Thoroughly rinse out the graduated cylinder with distilled water. Rinse a second time. Repeat this process to transfer 1M Cusoa, o.1 Mcusou and 1M Feso to each of their respective beakers. why is the use of clean glassware so important for these measurements? obtain 1 zinc plate, 2 copper wires, and 1 iron plate along with a piece of sand paper.Clean the surface of each of these electrodes with the sandpaper. Be sure to sand all sides of the electrodes and the entire length. DO NOT SAND DIRECTLY ON THE LAB BENCH. Place the electrode on a piece of scrap paper prior to sanding in order to protect the bench surface from scratches. When you have finished sanding, wipe the electrode with a damp paper towel to remove the dust particles followed by a dry paper towel. Record the appearance of the clean electrodes. Set up the electrochemical cells according to Figure 1 using the 1 M Zn(NO3)2 solution as the anode and the 1 M CuSOs solution as the cathode. Put the zinc electrode in the zinc solution and the copper electrode into the copper solution. Do not attach the salt bridge yet. At this point you are ready to connect the multimeter to the cells. Turn the multimeter dial to "DCN". Connect the black alligator clip (connected to the negative terminal of the multimeter) to the Zn electrode plate and the red alligator clip (connected to the positive terminal of the multimeter) to the copper wire. What voltage do you observe? Why? obtain 50 mL of 0.5 M KNo, and transfer to a 250 mL beaker. Place a strip of filter paper (provided at the front by the TA) into the KNO, solution and allow it to soak thoroughly. This filter paper will act as the salt bridge. It is very important that you do not allow this paper to dry out a any time during the experiment!!! If the paper becomes dry, re-soak it in the KNO3 solution.Explanation / Answer
Answer for question (3).
Le Chatelier's principle: It's a general principle suggesting that any changes in a system are temporary as the system readjusts itself and tries to attain original equilibrium.
In terms of a chemical reaction at equilibrium, changes in concentration, temperature, pressure and volume can bring changes in the system and the system tries to readjust itself to original equilibrium but only in a partial manner to counter the effects of such changes
An electrochemical cell with different concentrations of same kind of half cells is known as concentration cell, a kind of galvanic cell. They produce electricity because of reduction in the thermodynamic free energy of the electrochemical system. In the half-cells, the same reaction occurs but in opposite directions, increasing the lower and decreasing the higher concentration of half cells. In these concentration cells, the high concentration of metal ions will be cathodic and will be protected, and the area of metal in contact with the low metal ion concentration will be anodic and corroded. The potential difference in these cells is measured by Nernst equation.
Answer for question (4).
Electrochemical cells produced by Zinc electrode (zinc plate) in zinc salt solution (half cell) and Copper electrode (copper wire) in copper salt solution (half cell) which are connected by a salt bridge are known as Daniel cell. This is a standard electrochemical cell where copper oxidizes zinc. In these kind of cells zinc acts as anode (negative electrode, loss of electrons happens) and copper acts as cathods (positive electrode, gain of electrons happens). The total reaction in this is written as follows:
Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s) and the cell is represented as follows:
Zn I Zn2+ (1M) II Cu I Cu2+ (1M)
The electrical potential of the above cells can be determined by calculating the potentials for the two half cells involved. The electrode potential, E0, in volts, for each of the two half reactions is calculated by Nernst equation. Then the standard potential for the cell is equal to the more positive E0 value minus the more negative E0 value. This gives a positive voltage as observed in the above experiment.
In case of the following cell
Cu I Cu2+ (1M) II Zn I Zn2+ (1M)
the polarity is reversed and one observes a negative equal voltage .
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