Sulfuric acid
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Sulfuric (or sulphuric) acid, H2SO4, is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry. World production in 2001 was 165 million tonnes, with an approximate value of US$8 billion. Principal uses include ore processing, fertilizer manufacturing, oil refining, wastewater processing, and chemical synthesis.
Many proteins are made of sulfur-containing amino acids (such as cysteine and methionine) which produce sulfuric acid when metabolized by the body.
Contents
Occurrence
Pure (undiluted) sulfuric acid is not encountered on Earth, due to sulfuric acid's great affinity for water. Apart from that, sulfuric acid is a constituent of acid rain, which is formed by atmospheric oxidation of sulfur dioxide in the presence of water - i.e., oxidation of sulfurous acid. Sulfur dioxide is the main byproduct produced when sulfur-containing fuels such as coal or oil are burned.
Sulfuric acid is formed naturally by the oxidation of sulfide minerals, such as iron sulfide. The resulting water can be highly acidic and is called Acid Mine Drainage (AMD). This acidic water is capable of dissolving metals present in sulfide ores, which results in brightly-colored, toxic streams. The oxidation of iron sulfide pyrite by molecular oxygen produces iron(II), or Fe2+:
2 FeS2 + 7 O2 + 2 H2O → 2 Fe2+ + 4 SO42− + 4 H+.
The Fe2+ can be further oxidized to Fe3+, according to:
4 Fe2+ + O2 + 4 H+ → 4 Fe3+ + 2 H2O,
and the Fe3+ produced can be precipitated as the hydroxide or hydrous oxide. The equation for the formation of the hydroxide is
Fe3+ + 3 H2O → Fe(OH)3 + 3 H+.
The iron(III) ion ("ferric iron", in casual nomenclature) can also oxidize pyrite. When iron(III) oxidation of pyrite occurs, the process can become rapid. pH values below zero have been measured in ARD produced by this process.
ARD can also produce sulfuric acid at a slower rate, so that the Acid Neutralization Capacity (ANC) of the aquifer can neutralize the produced acid. In such cases, the Total Dissolved solids (TDS) concentration of the water can be increased form the dissolution of minerals from the acid-neutralization reaction with the minerals.
[edit] Extraterrestrial sulfuric acid
[edit] The cycle, in atmosphere of Venus
Sulfuric acid is produced in the upper atmosphere of Venus by the Sun's photochemical action on carbon dioxide, sulfur dioxide, and water vapor. Ultraviolet photons of wavelengths less than 169 nm can photodissociate carbon dioxide into carbon monoxide and atomic oxygen.
Atomic oxygen is highly reactive. When it reacts with sulfur dioxide, a trace component of the Venusian atmosphere, the result is sulfur trioxide, which can combine with water vapor, another trace component of Venus's atmosphere, to yield sulfuric acid.
CO2 → CO + O
SO2 + O → SO3
SO3 + H2O → H2SO4
In the upper, cooler portions of Venus's atmosphere, sulfuric acid exists as a liquid, and thick sulfuric acid clouds completely obscure the planet's surface when viewed from above. The main cloud layer extends from 45–70 km above the planet's surface, with thinner hazes extending as low as 30 and as high as 90 km above the surface.
The permanent venusian clouds produce a concentrated acid rain, as the clouds on the atmosphere of Earth produce water rains.
Thus, it's exist a double combined cycle of sulfur dioxide and water, because when sulfuric drops fall down, they are heated up and release water vapor, becoming more and more concentrated. And when they reach above 300°C, sulfuric acid begins to decompose in sulfur trioxide and water (both gaseous). sulfur trioxide is highly reactive (like sulfuric acid) and become sulfuric dioxide and oxygen, which oxides traces of CO, or surface rocks.
Sulfuric dioxide and water (vapor) continuously equilibrate their pressure from deep venusian atmosphere to upper altitudes, where they will be transformed again in sulfuric acid, and the cycle is closed !
[edit] On Europa's icy surface
Infrared spectra from NASA's Galileo mission show distinct absorptions on Jupiter's moon Europa that have been attributed to one or more sulfuric acid hydrates. The interpretation of the spectra is somewhat controversial. Some planetary scientists prefer to assign the spectral features to the sulfate ion, perhaps as part of one or more minerals on Europa's surface.
Many proteins are made of sulfur-containing amino acids (such as cysteine and methionine) which produce sulfuric acid when metabolized by the body.
Contents
Occurrence
Pure (undiluted) sulfuric acid is not encountered on Earth, due to sulfuric acid's great affinity for water. Apart from that, sulfuric acid is a constituent of acid rain, which is formed by atmospheric oxidation of sulfur dioxide in the presence of water - i.e., oxidation of sulfurous acid. Sulfur dioxide is the main byproduct produced when sulfur-containing fuels such as coal or oil are burned.
Sulfuric acid is formed naturally by the oxidation of sulfide minerals, such as iron sulfide. The resulting water can be highly acidic and is called Acid Mine Drainage (AMD). This acidic water is capable of dissolving metals present in sulfide ores, which results in brightly-colored, toxic streams. The oxidation of iron sulfide pyrite by molecular oxygen produces iron(II), or Fe2+:
2 FeS2 + 7 O2 + 2 H2O → 2 Fe2+ + 4 SO42− + 4 H+.
The Fe2+ can be further oxidized to Fe3+, according to:
4 Fe2+ + O2 + 4 H+ → 4 Fe3+ + 2 H2O,
and the Fe3+ produced can be precipitated as the hydroxide or hydrous oxide. The equation for the formation of the hydroxide is
Fe3+ + 3 H2O → Fe(OH)3 + 3 H+.
The iron(III) ion ("ferric iron", in casual nomenclature) can also oxidize pyrite. When iron(III) oxidation of pyrite occurs, the process can become rapid. pH values below zero have been measured in ARD produced by this process.
ARD can also produce sulfuric acid at a slower rate, so that the Acid Neutralization Capacity (ANC) of the aquifer can neutralize the produced acid. In such cases, the Total Dissolved solids (TDS) concentration of the water can be increased form the dissolution of minerals from the acid-neutralization reaction with the minerals.
[edit] Extraterrestrial sulfuric acid
[edit] The cycle, in atmosphere of Venus
Sulfuric acid is produced in the upper atmosphere of Venus by the Sun's photochemical action on carbon dioxide, sulfur dioxide, and water vapor. Ultraviolet photons of wavelengths less than 169 nm can photodissociate carbon dioxide into carbon monoxide and atomic oxygen.
Atomic oxygen is highly reactive. When it reacts with sulfur dioxide, a trace component of the Venusian atmosphere, the result is sulfur trioxide, which can combine with water vapor, another trace component of Venus's atmosphere, to yield sulfuric acid.
CO2 → CO + O
SO2 + O → SO3
SO3 + H2O → H2SO4
In the upper, cooler portions of Venus's atmosphere, sulfuric acid exists as a liquid, and thick sulfuric acid clouds completely obscure the planet's surface when viewed from above. The main cloud layer extends from 45–70 km above the planet's surface, with thinner hazes extending as low as 30 and as high as 90 km above the surface.
The permanent venusian clouds produce a concentrated acid rain, as the clouds on the atmosphere of Earth produce water rains.
Thus, it's exist a double combined cycle of sulfur dioxide and water, because when sulfuric drops fall down, they are heated up and release water vapor, becoming more and more concentrated. And when they reach above 300°C, sulfuric acid begins to decompose in sulfur trioxide and water (both gaseous). sulfur trioxide is highly reactive (like sulfuric acid) and become sulfuric dioxide and oxygen, which oxides traces of CO, or surface rocks.
Sulfuric dioxide and water (vapor) continuously equilibrate their pressure from deep venusian atmosphere to upper altitudes, where they will be transformed again in sulfuric acid, and the cycle is closed !
[edit] On Europa's icy surface
Infrared spectra from NASA's Galileo mission show distinct absorptions on Jupiter's moon Europa that have been attributed to one or more sulfuric acid hydrates. The interpretation of the spectra is somewhat controversial. Some planetary scientists prefer to assign the spectral features to the sulfate ion, perhaps as part of one or more minerals on Europa's surface.
