Hoffman voltameter used to electrolyze water.

Electrolysis of Water is an electrolytic process which decomposes water into oxygen and hydrogen gas with the aid of an electric current, where a power source from a 6 volt battery is commonly used. The electrolysis cell consists of two electrodes (usually an inert metal such as platinum) submerged in an electrolyte and connected to opposite poles of a source of direct current. Image File history File links Hoffman_voltameter. ... Image File history File links Hoffman_voltameter. ... Hofmann voltameter as described. ... It has been suggested that Electrolytic process be merged into this article or section. ... This article describes water from a scientific and technical perspective. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Lightning strikes during a night-time thunderstorm. ... Josephson junction array chip developed by NIST as a standard volt. ... An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... In English, to be inert is to be in a state of doing little or nothing. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms positive ions (cations) and has metallic bonds. ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Atomic mass 195. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ...

The electric current disassociates water molecule into hydroxide and hydrogen ions. This article describes water from a scientific and technical perspective. ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... ...

In the electrolytic cell, at the cathode, hydrogen ions accept electrons in a reduction reaction that forms hydrogen gas: Diagram of a copper cathode in a Daniells cell. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... Semi-accurate illustration of a redox reaction Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ...

At the anode, hydroxide ions undergo an oxidation reaction and give up electrons to the anode to complete the circuit and form water and oxygen gas: Diagram of a zinc anode in a galvanic cell. ... The most fundamental reactions in chemistry are the redox processes. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ...

hence decomposing water into Oxygen and Hydrogen;

The volume of hydrogen gas produced is therefore twice the amount of oxygen gas. Assuming equal temperature and pressure for both gases, the hydrogen gas has twice the volume of the oxygen.

Hoffman voltameter connected to a direct current power source converter.

---

This image has an uncertain copyright status and is pending deletion. You can comment on the removal.

Image File history File links Elektrolyse1. ... Image File history File links Elektrolyse1. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... A switched-mode power supply, switch-mode power supply, or SMPS, is an electronic power supply unit (PSU) that incorporates a switching regulator — an internal control circuit that switches power transistors (such as MOSFETs) rapidly on and off in order to stabilize the output voltage or current. ...

Electrolyte selection

Main article: Electrolyte

As pure water conducts electricity very poorly, a water-soluble electrolyte must be added to the electrolysis cell to close the circuit. The electrolyte dissolves and disassociates into cations and anions (positive and negative ions) that carry the current. Electrolytes are normally acids, bases, or salts. An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... Water is a chemical substance that is essential to all known forms of life. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... An ion is an atom or group of atoms with a net electric charge. ... ... ... For alternative meanings see acid (disambiguation). ... The best STM agency in the world ... For other meanings of the word salt see table salt or salt (disambiguation). ...

Care must be taken in choosing an electrolyte, since an anion from the electrolyte is in competition with the hydroxide ions to give up an electron. An electrolyte anion with less standard electrode potential than hydroxide will be oxidized instead of the hydroxide, and no oxygen gas will be produced. A cation with a greater standard electrode potential than a hydrogen ion will be reduced in its stead, and no hydrogen gas will be produced. An anion is an ion with negative charge. ... The electron is a fundamental subatomic particle that carries an electric charge. ... An anion is an ion with negative charge. ... It has been suggested that Electrode potential be merged into this article or section. ... A cation is an ion with positive charge. ... It has been suggested that Electrode potential be merged into this article or section. ...

The following cations have lower electrode potential than H⁺ and are therefore suitable for use as electrolyte cations: Li⁺, Rb⁺, K⁺, Cs⁺, Ba²⁺, Sr²⁺, Ca²⁺, Na⁺, and Mg²⁺. Sodium and lithium are frequently used, as they form inexpensive, soluble salts. An ion is an atom or group of atoms with a net electric charge. ... General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/grey Atomic mass 6. ... General Name, Symbol, Number rubidium, Rb, 37 Chemical series alkali metals Group, Period, Block 1, 5, s Appearance grey white Atomic mass 85. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ... General Name, Symbol, Number caesium, Cs, 55 Chemical series alkali metals Group, Period, Block 1, 6, s Appearance silvery gold Atomic mass 132. ... General Name, Symbol, Number barium, Ba, 56 Chemical series alkaline earth metals Group, Period, Block 2, 6, s Appearance silvery white Atomic mass 137. ... General Name, Symbol, Number strontium, Sr, 38 Chemical series alkaline earth metals Group, Period, Block 2, 5, s Appearance silvery white metallic Atomic mass 87. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/grey Atomic mass 6. ...

If an acid is used as the electrolyte, the cation is H⁺, and there is no competitor for the H⁺ created by disassociating water. An acid (often represented by the generic formula HA) is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a pH of less than 7. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ...

The most commonly used anion is SO₄^2-, as it is very difficult to oxidize. An anion is an ion with negative charge. ...

Standard potential for oxidation of this ion to the peroxydisulfate ion is −2.05 volts.

Strong acids such as Sulfuric acid (H₂SO₄) are frequently used as electrolytes. Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ...

Techniques

This reaction is simple to replicate. Two leads running from the terminals of a battery into a cup of water and electrolyte are sufficient to produce a visible stream of oxygen or hydrogen bubbles at either electrode. The presence of hydroxide (OH^-) ions can be detected with a pH indicator such as phenolphthalein or Bromothymol blue. An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... ... A pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH (acidity or alkalinity) of the solution can be determined easily. ... Phenolphthalein is a sensitive chemical with the formula C20H14O4 (often written as HIn in chemistry shorthand notation). ... Bromothymol blue (alt: dibromothymolsulfonephthalein, bromthymol blue, BTB) is a chemical indicator for weak acids and bases. ...

Match test used to detect the presence of Hydrogen.

---

This image has an uncertain copyright status and is pending deletion. You can comment on the removal.

Image File history File links Elektrolyse2. ... Image File history File links Elektrolyse2. ...

Hofmann voltameter

Main article: Hofmann voltameter

The Hofmann voltameter is often used as a small-scale electrolytic cell. It consists of three joined upright cylinders. The inner cylinder is open at the top to allow the addition of water and the electrolyte. A platinum electrode is placed at the bottom of each of the two side cylinders, connected to the positive and negative terminals of a source of electricity. When current is run through the hofmann voltameter, gaseous oxygen forms at the anode and gaseous hydrogen at the cathode. Each gas displaces water and collects at the top of the two outer tubes, where it can be drawn off with a stopcock. The Hofmann voltameter is not, in fact, a meter but an apparatus used for the electrolysis of water. ... Water is a chemical substance that is essential to all known forms of life. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Atomic mass 195. ... Lightning strikes during a night-time thunderstorm. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... Diagram of a zinc anode in a galvanic cell. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Diagram of a copper cathode in a Daniells cell. ...

Industrial electrolysis

Many industrial electrolysis cells are very similar to Hofmann voltameters, with complex platinum plates or honeycombs as electrodes. Hydrogen gas is usually created, collected, and burned on the premises, as its energy density per volume is too low to make transporting or storing it economically feasible. Oxygen gas is treated as a byproduct. The Hofmann voltameter is not, in fact, a meter but an apparatus used for the electrolysis of water. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ...

High-temperature electrolysis

Main article: High-temperature electrolysis

High-temperature electrolysis (also HTE or steam electrolysis) is a method currently being investigated for water electrolysis with a heat engine. High temperature electrolysis is more efficient than traditional room-temperature electrolysis because some of the energy is supplied as heat, which is cheaper than electricity, and because the electrolysis reaction is more efficient at higher temperatures. High-temperature electrolysis schema. ... In engineering and thermodynamics, a heat engine performs the conversion of heat energy to mechanical work by exploiting the temperature gradient between a hot source and a cold sink. Heat is transferred from the source, through the working body of the engine, to the sink, and in this process some...

Applications

About four percent of hydrogen gas produced worldwide is created by electrolysis, and normally used onsite. Hydrogen is used for the creation of ammonia for fertilizer via the Haber process, and converting heavy petroleum sources to lighter fractions via hydrocracking. There is some speculation about future development of hydrogen as an energy carrier. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... The Haber Process (also Haber-Bosch process) is the reaction of nitrogen and hydrogen to produce ammonia. ... Pumpjack pumping an oil well near Sarnia, Ontario Ignacy Łukasiewicz - inventor of the refining of kerosene from crude oil. ... In petroleum geology and chemistry, cracking is the process whereby complex organic molecules (e. ... A hydrogen economy is a hypothetical future economy in which energy, for mobile applications (vehicles, aircraft) and electrical grid load balancing (daily peak demand reserve), is stored as hydrogen (H2). ...

Efficiency

The energy efficiency of water electrolysis varies widely. Some report 50–70%[1], while others report 80–94%.[2] These values refer only to the efficiency of converting electrical energy into hydrogen's chemical energy. The energy lost in generating the electricity is not included. For instance, when considering a power plant that converts the heat of nuclear reactions into hydrogen via electrolysis, the total efficiency is more like 25–40%.[3] In physics and engineering, including mechanical and electrical engineering, energy efficiency is a dimensionless number, with a value between 0 and 1 or with times 100 given in percent. ...

See also

Listen to this article · (info)

This audio file was created from an article revision dated 2006-07-21, and may not reflect subsequent edits to the article. (Audio help)

More spoken articles

   

• Electrochemistry
• Electrolysis
• Hydrogen production
• Gas cracker

Image File history File links Sound-icon. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... July 21 is the 202nd day (203rd in leap years) of the year in the Gregorian Calendar, with 163 days remaining. ... Image File history File links Sound-icon. ... English chemists John Daniell (left) and Michael Faraday (right), both credited to be founders of electrochemistry as known today. ... It has been suggested that Electrolytic process be merged into this article or section. ... Hydrogen production is done in bulk today from hydrocarbon fossil fuels via a chemical path. ... A gas cracker is any device that splits the molecules in a gas or liquid, usually by electrolysis, into atoms. ...

References

• Electrolysis of Water. Experiments on Electrochemistry. Retrieved on November 20, 2005.
• Electrolysis of Water. Do Chem 044. Retrieved on November 20, 2005.