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Process of Electrolysis

Question

How is hydrogen produced from the process of electrolysis?

2 years ago

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13 Replies

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N

Norbert Mayer


13 Answers

K
Komalam Lakshmanan Lalitha

Solid Oxide Electrolyzers

Water at the cathode combines with electrons from the external circuit to form hydrogen gas and negatively charged oxygen ions. The oxygen ions pass through the solid ceramic membrane and react at the anode to form oxygen gas and generate electrons for the external circuit.


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Hydrogen can be produced by the splitting of water by electrolysis. The formula of water is H2O so the process produces both hydrogen gas and oxygen gas. Water is an unusual covalent substance in that it can dissociate into ions, H+ and OH-, and it is this dissociation (which only occurs to a small extent) that makes the process possible.

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The answer is really straightforward Norbert. Water is H2O. So that means it has 2 H atoms. When electricity passed through water one of the H atoms splits off and forms an H+ ion ( the other ion formed is OH-; remember that the two ions - H+ and OH-must add up to H2O and there must be a balance of the + and - charges to make the water molecule neutral overall.


So Norbert we know that opposites attract so the H+ ion (has a positive charge) is attracted to the negative electrode that is there delivering the electricity passing through the water.


When the H+ arrives at the electrode it gains an electron to become a neutral H atom ( the negative electron cancels the positive charge; remember that the H+ ion is a Hydrogen atom without an electron - think back to the work on atoms and electronic structure).


So now we have a neutral H atom. But H atoms are not stable and don't like being on their own ( again think back to electronic structure and H atoms only have one electron in the first electron shell and the shell is stable if it has 2.


So what does the H atom do to fill its first shell and become stable? It shares an electron with another H atom and becomes H2 a hydrogen molecule. This if you recall is covalent bonding. Remember it is covalent bonding that happens between non metals and where atoms share electrons to become stable.


I hope that helps you understand the answer to the question you asked. But please ask another question back if there are any parts you are unclear about. Well done for asking such a good question!


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Hydrogen is made using electrolysis of water. Electricity is used to split the molecule into hydrogen and oxygen. Because water alone is not a good electrical conductor weak salt solutions or weak acids are usually added to increase the conductivity during the process. A DC voltage is placed across electrodes inserted into the water mix ( called an electrolyte). At the negatively charged electrode or 'cathode', a reaction takes place, with electrons (e) from the cathode being given to hydrogen cations to form hydrogen gas. The reaction is 2 H+(aq) + 2e → H2(g).

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Q
Qurra

electrolysis is the process of using electricity to split water into hydrogen and oxygen.

this reaction takes place in a unit called the electrolyser.

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Hi!

Electrolysis requires an ionic compound (so for example, water, table salt - NaCl, etc). If we electrolysise water alone, then the hydrogen component of the water (which is an H+ ion) is attracted to the cathode (which is negatively charged and attracts positive ions, which are sometimes called cations). The H+ ion contacts the cathode, loses its charge, and the neutral Hydrogen atom is released and can be collected in a test tube. You can confirm that it is hydrogen you collected by doing the Squeaky pop test :)


Interestingly, due to the reactivity series, when you dissolve NaCl into the water and make Na+ and Cl- ions, H+ is less reactive than Na+ and so electrolysis will still attract the H+ ions instead of the Na+ ions, which will instead really want to react with the stuff already in the water. That is why in this electrolysis reaction, you produce hydrogen and chlorine, not sodium and chlorine.

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P
Pujan Fanju

Water contains positively charged hydrogen ions (H+) and negatively charge Hydroxide ions (OH-). When a direct current is passed through the electrodes, the cations (H+) are attracted to the cathode (negatively charged electrode) and gain electrons and form Hydrogen (H2). The anions (OH-) also get attracted to the anode to form oxygen after losing electrons.

D
Duman Bakayev

When water molecules are electrolyzed there are two options for each molecule. A molecule can go to the cathode or to the anode. As we need hydrogen I will explain what happens at the cathode. The cathode is the electrode that receives electrons from the power supply. Therefore, the cathode shares the electrons it receives with anything that comes nearby. If water comes close enough to the cathode a reaction takes place. If you look at formal charges H has a "+" and O has a "-". We know that electrons are negatively charged, hence only hydrogen will be able to receive them. Hydrogen is still in the molecule, so H2O + electrons will give H2 and will leave the OH^(-). In order to understand the reaction is easy to imagine H2O as HOH, so we take two Hs from two HOH, combine them into H2 and two OH^(-) particles will be left. From that, we can see that two H+ will need two electrons. The final reaction will be H2O + 2e -> H2 + 2OH^(-).

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Dihydrogen molecules (H2) are produced through splitting water (H2O) molecules in their constituents oxygen and hydrogen atoms by applying an electric potential. In particular, the electrolysis reaction could be written as:


2(H2O) ---> 2(H2) + O2 V = +1.23 V


Meaning that by applying an electric potential of V = +1.23 V, two molecules of water will be split into 2 dihydrogen molecules and one dioxygen molecule.


In particular, the H atoms in H2O will get reduced and the O atoms oxidised.



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K
Kürşat Emre

In the electrolysis method, also known as the water separation method, water is separated into hydrogen and oxygen by passing an electric current between two electrodes. Commercial low temperature electrolysis systems have efficiencies between 56% and 73%.

R
Rebeca Athina

Steam at the cathode combines with electrons from the external circuit to form hydrogen gas and negatively charged oxygen ions. The oxygen ions pass through the solid ceramic membrane and react at the anode to form oxygen gas and generate electrons for the external circuit.

Z
Zalihe Halil

During the electrolysis of aqueous solutions, water molecules dissociate to produce H+ and OH- ions. The positively charged H+ and metal ions are attracted to the cathode, which is the negative electrode. If the metal is higher in the reactivity series than hydrogen, then hydrogen gas will be produced at the cathode. The reason behind this is that ions which are more reactive will remain in the solution whereas the least reactive ion will be discharged. This process is evident with the process of bubble formation at the cathode.

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If a metal is more reactive than Hydrogen, then the H+ ions will be discharged at the cathode. The H+ ions will be gaining one electron (reduction), and once they become an atom, they will bond covalently with another hydrogen atom, forming hydrogen gas. The overall equation is: 2H+ + 2e- —> H2

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