I attach the numbers of the experement of Electrode Potential and its Measuremen

Question

I attach the numbers of the experement of Electrode Potential and its Measurement (please answer all the parts) and this is the procedure that we had done.

Objective:

To measure the electrode potential and Redox potential of various metals & alloys using calomel reference electrode (SCE).

Experimental Procedure:

I. Measurement of electrode potential:

1.   Prepare two small cylindrical specimens one made from Carbon Steel (CS) and the other made from Stainless Steel (SS), so as to fit the specimen holder of spherical ASTM flask. -

2.   Immerse each of the small cylindrical specimen (SS and CS) in the ASTM flask containing tap water, and brine respectively.

3    Using the digital voltmeter and a Saturated Calomel Reference Electrode (SCE), measure the potential of the SS in tap water, and in brine. Also measure the potential of the CS in same two environments.

II. Measurement of Potential in standard and non-standard conditions:

[Verification of Nernst Equation]

1.Prepare 1-M solutions of Zn+2 and Cu+2.

2.Measure the potential E0 (Zn / Zn+2 ) and E0 (Cu / Cu+2 ) in standard condition using Saturated Calomel Reference Electrode (SCE).

Measure the potential E (Zn / Zn+2 ) and E (Cu / Cu+2 ) in non-standard condition (0.5-M solutions) using Saturated Calomel Reference Electrode (SCE)

1.Determine the potentials measured in non-standard condition using Nernst Equation given below:

E = E0 + (0.0592 / n) log (Cion) Where E0 = standard electrode potential

                                 n = number of electrons transferred

                                              Cion = concentration of metal in molar units

Discussion:

1. CS in tap water develops different potential from that of SS in same environment. Explain why?

2. From the measured value of CS potential in tap water, determine whether it corrodes or not, knowing   

    that E0(Fe/Fe+2) = - 440 mV vs. Standard Hydrogen Electrode (SHE.).

3. CS in tap water develops different potential from that of CS in brine. Explain why?

4. Are the measured values of potential (E0) for Zn / Zn+2 and Cu / Cu+2 under standard   

    conditions same as those given in the text book? If Not, explain why?

Explanation / Answer

1) carbon steel is made up of iron and carbon while stainless steel is made up of chromium and iron.

And reduction potential of two alloys are different based on the metals used.

2) The reduction potential of CS is less than that of hydrogen, so it will be more reactive or more prone to oxidation and will corrode

3) Due to difference in the environment the tendancy to undergo oxidation / reduction changes.

In water we are considering only hydrogen reduction while in Brine there are salts as well

4) They are not exactly same, may be due to some error in measurements or due to difference in temperature conditions.

As standard reduction potential depends upon the temperature, pressure and concentration (1M)

5) The E is givne as

E = E0 - 0.0592 / n log [1/M+2]

So if we decrease the conncentration of metal ion, then the vale of log (1/[M]) will increase which will decrease the E cell value

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