Electrolysis of Iron(II)Sulphate

In summary, Iron(II)sulphate is reduced at the anode to form Iron, while water is reduced at the cathode to form hydrogen gas.
  • #1
hms.tech
247
0

Homework Statement



I am given a 1 M solution of Iron(II)sulphate(aq) and it is being electrolyzed using inert electrodes . What will form on the cathode ?

Homework Equations



Reduction potentials of : Fe =-0.44V
1.PNG

of water to from hydrogen : -0.83V

The Attempt at a Solution


Since iron(II) ion has a more POSITIVE value it is easily reduced at the cathode to form Iron (solid).

Unfortunately this answer is wrong .
The correct answer is Hydrogen will be formed on the cathode ... Why ?
 
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  • #2
Please help me !
 
  • #3
hms.tech said:
of water to from hydrogen : -0.83V

Please elaborate.

Generally speaking hydrogen gets reduced at 0 V by definition, doesn't it?
 
  • #4
Borek said:
Please elaborate.

Generally speaking hydrogen gets reduced at 0 V by definition, doesn't it?

It does indeed but that is something different. In this particular example we have :

Fe(II) ions , water molecules, extremely low number of Hydrogen ions and hydroxide ions, Sulphate ions .

Since the concentration of Hydrogen ions is almost negligible (as is the case in any aqueous solution) it should be OK to ignore them . So to form hydrogen gas at the cathode the reaction that occurs (in reality) is :

2 water molecules + 2 electrons → one molecule of hydrogen gas + 2 hydroxide ions with a standard redox potential of -0.83V
 
  • #5
hms.tech said:
Since the concentration of Hydrogen ions is almost negligible (as is the case in any aqueous solution) it should be OK to ignore them . So to form hydrogen gas at the cathode the reaction that occurs (in reality) is :

2 water molecules + 2 electrons → one molecule of hydrogen gas + 2 hydroxide ions with a standard redox potential of -0.83V

No, that's not a correct approach. To be exact you should not just ignore H+ presence, but take into account everything, including partial pressure of hydrogen (good luck with, as it is initially zero), and plug it all into the Nernst equation. You should do the same with your other reaction, remembering that initial concentration of OH- is not zero either (actually it is identical to the initial concentration of H+), and that -0.83 V is given for a solution in a standard state (which means concentration of OH- equal to 1M).

This is by no means a trivial prediction, but as long as you are not expected to do a very thorough analysis, just comparing -0.44 V with 0 V should do. Perhaps with some estimate of the H+ reduction potential based on just pH.
 

Related to Electrolysis of Iron(II)Sulphate

1. What is electrolysis of Iron(II)Sulphate?

Electrolysis of Iron(II)Sulphate is a chemical process that uses electricity to split Iron(II)Sulphate into its component elements - iron, sulfur, and oxygen. It involves passing an electric current through a solution of Iron(II)Sulphate, which causes the ions in the solution to migrate towards the electrodes and undergo chemical reactions.

2. What are the materials needed for electrolysis of Iron(II)Sulphate?

The materials needed for electrolysis of Iron(II)Sulphate include Iron(II)Sulphate solution, a power source (such as a battery or power supply), two electrodes (typically made of carbon or platinum), wires to connect the electrodes to the power source, and a beaker or container to hold the solution.

3. What are the products of electrolysis of Iron(II)Sulphate?

The products of electrolysis of Iron(II)Sulphate depend on the concentration of the solution and the type of electrodes used. Generally, the products can include iron metal, sulfur dioxide gas, and oxygen gas. The iron metal will collect on the cathode (negative electrode) while the sulfur dioxide and oxygen gas will be released at the anode (positive electrode).

4. What are the applications of electrolysis of Iron(II)Sulphate?

Electrolysis of Iron(II)Sulphate has several industrial applications, including the production of iron metal, purification of metals, and the creation of sulfuric acid. It can also be used in educational settings to demonstrate the principles of electrolysis and chemical reactions.

5. What are the safety precautions for electrolysis of Iron(II)Sulphate?

When performing electrolysis of Iron(II)Sulphate, it is important to handle the solution and electrodes with caution as they may be corrosive or produce harmful gases. It is recommended to wear protective gloves and eyewear, work in a well-ventilated area, and dispose of the solution properly after the experiment. It is also important to disconnect the power source before handling the electrodes or solution.

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