View source for Sulfuric acid

{{Compound|name=Sulfuric acid|chemf=H2SO4|stp_p=liquid|stp_q=oily|mm=98.79|density=1.84|mp=10|bp=337|pKal=−3, 1.99|group=Mineral Acids|nfpa_h=3|nfpa_r=2|nfpa_o=<s>W</s>|industrial=yes|sol_aq=misc|azeo_aq_ww=98|azeo_aq_mm=88.5|azeo_aq_vv=95.8}}
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Sulfuric acid is a strong acid. It is not ''the'' strongest acid, but it is arguably the source of most other acids, weaker or stronger. In fact, according to most sources, sulfuric acid is the primary industrial chemical on earth, and a nation's ability to produce it may be a good indicator of it's industrial strength.
==Uses==
===Primary===
* Sulfuric acid is the preeminent [[:Category:Industrial Chemicals| industrial chemical]].
* The precursor to many mineral acids including [[hydrochloric acid]], [[phosphoric acid]] and [[nitric acid]]

===Secondary===
* purification of [[copper]]
* in lead-acid [[voltaic cell]]s
* as a chemical dehydrating agent, particularly during nitration of hydrocarbons.
==Natural Occurrence==
* Sulfuric acid '''does''' occur naturally, primarily in post-volcanic acid rain and as acidic rock drainage from sulfide minerals.

==Hazards==
'''N.B.''' Sulfuric acid is among the most hazardous chemicals we list in this project. Treat it with the utmost care.
* Sulfuric acid will dissolve most metals and virtually all organic matter. Spills of concentrated acid are often essentially unfixable: adding a correspondingly strong alkali in the hopes of neutralizing the acid can result in even more heat being produced and splatters of acid (and concentrated alkali) flying in all directions. Sometimes it is best to wait until the reactions stop of their own accord, then repair the damage.
* Sulfuric acid, in the process of breaking down most organics, produces substantial amounts of heat. Often enough to start fires where there were none before. In fact, a mixture of sulfuric acid added to organics was (for a while) used as a fire starting mechanism before reliable strike matches were available. Be very careful.
==Character==
===Stoichiometry===
: 228g (190.5L, a sphere with R=35.66cm, D=71.32cm, or a cube 58cm on an edge) of (dry, 20&deg;C) air contains 1.5 mol of {{#Chem: O2}}. (48g or 3 mol of O)
: 32g (16cc) of sulfur contains 1 mol of {{#Chem: S}}
: 18g (18cc) of water contains 1 mol of {{#Chem: H2O}}
So...
: 1.5 mol {{#Chem: O2}} + 1 mol S + 1 mol {{#Chem: H2O}} = 1 mol {{#Chem: H2SO4}}
: 48g {{#Chem: O2}} + 32g S + 18g water = 98g {{#Chem: H2SO4}}

==Production==
===Synthesis===
====via other mineral acids====
See [[mineral acid intraconversion]]
====via electrolysis====
=====electrobromine=====
=====copper sulfate=====
Using a copper anode, and a graphite, platinum, lead, or lead dioxide anode, pass 300-600 Am<sup>-2</sup> at 1-2.5V through a concentrated solution of [[copper sulfate]]:
: {{#Chem: 2CuSO4(aq) + 2H2O {= 1-2.5V } 2Cu(s) + 2H2SO4(aq) + O2(g)}}
=====magnesium sulfate=====
Using a porous ceramic partition (such as a low-fired clay pot)draw the sulfate through the partition  and form sulfuric acid on the anode side, leaving magnesium hydroxide on the cathode side of the partition. pH paper should show progressively more acidity in the anolyte and more alkalinity on the cathode side.
====via sulfur <u>tri</u>oxide====
Sulfuric acid is produced by dissolving [[sulfur trioxide]] in water. This is a very exothermic reaction.
: {{#Chem:  H2O + SO3 = H2SO4 }}
: cf. [[Chamber process]]
====via sulfur <u>di</u>oxide====
One way to bypass sulfur trioxide is to oxidize the [[sulfur dioxide]] ''in situ'' using an oxidizer:
<div style='margin-left:2em;'>
=====hydrogen peroxide=====
Bubble [[sulfur dioxide]] through [[hydrogen peroxide]], producing sulfuric acid directly:
: {{#Chem: H2O2(l) + SO2(g) = H2SO4(l)}}
=====potassium permanganate=====
Bubble [[sulfur dioxide]] through a solution of [[potassium permanganate]], producing sulfuric acid
: {{#Chem:5SO2 + 2KMnO4 + 2H2O → 2H2SO4 + 2MnSO4 + K2SO4}}
=====copper chloride=====
[[Sulfur dioxide]] will reduce two molecules of [[copper (II) chloride]] and in turn be oxidized to SO3 which immediately reacts with water producing sulfuric acid. The remaining hydrogens pick up the freed chlorine and make [[hydrochloric acid]].<ref>{{cite web|url=https://www.youtube.com/watch?v=l2AkVYxDSKc|title=Make Sulfuric Acid by the Copper Chloride Process|courtesy=Youtube/Nurdrage}}</ref>
# Bubble [[sulfur dioxide]] through a concentrated solution of [[copper (II) chloride]], giving [[sulfuric acid]], [[hydrochloric acid]] and [[copper (I) chloride]]. 
#: {{#Chem: SO2(g) + 2 CuCl2(aq) + 2 H2O = H2SO4(aq) + 2 HCl(aq) + 2 CuCl(aq)}}
#:  64.066 + 2(134.45) + 2(18.015) &rarr; 98.079 + 2(36.46) + 2 (98.999)
#:  64.066 + 268.9 + 36.03 &rarr; 98.079 + 72.92 + 197.998
#:   368.996 &rarr; {{pm|368.997|0.001}}
#: So approximately  64ubm of sulfur dioxide will be absorbed by approximately 305ubm of solution giving 369ubm of product, including approximately 98ubm of [[sulfuric acid]]
#: '''NB:''' The solubility of CuCl2 in water at 25&deg;C is 1:10.2, so you can't dissolve 2 moles of CuCl2 in 2 moles of water. Therefor, there will either be undissolved CuCl2 or an excess of water when the reaction begins.
# Decant/Filter the solid copper salts as needed, leaving mixed acids with some small amount of dissolved copper salts
# Distill off the hydrochloric acid
#: {{#Chem:H2SO4(aq) + HCl(aq) {= ~100&deg;C} H2SO4(aq) +  HCl(g) // possibly also CuSO4(s) and CuCl(s) on both sides}}
# Decant/Filter the solid copper salts as needed, leaving [[sulfuric acid]]
# Regenerate HCl/CuCl solution to {{#Chem:CuCl2(aq)}} by bubbling air through it
#: {{#Chem: 4HCl(aq) + 4CuCl(aq) + O2(g) = 4CuCl2(aq) + 2H2O(l)}}

==Purification==
===Sulfuric acid vs dissolved sulfur dioxide===
====drying====
Water with dissolved sulfur dioxide will dry completely under moderate airflow. [[sulfuric acid]] will not evaporate at OTP to any great degree.
# Take a small sample, spread it out on a warm dry surface.
#: '''Danger''': The other possibility is that this is [[sulfuric acid]], so the surface and the device used to spread the solution should be acid tolerant!
# Smell the spread-out solution.
# If it smells of eggs, or emits a greyish gas, you've got substantial dissolved sulfur dioxides.
# Attempt to air-dry the solution by blowing air over it
# If it dries completely from airflow at OTP, there was (essentially) no sulfuric acid present.
====boiling====
[[Sulfur dioxide]] is soluble in water at lower temperatures, but much less so at elevated ones. Check the pH of a sample the solution, boil it to half its volume, and check again. If the pH has decreased (become more acidic) even slightly, then the solution is mostly [[sulfuric acid]]. If the pH has increased, then the solution was mostly dissolved [[sulfur dioxide]].
==Testing==

===Concentration===
{| class="wikitable"
|-
! Mass fraction<br />H<sub>2</sub>SO<sub>4</sub>
! Density<br />(kg/L)
! Concentration<br />(mol/L)
! Common name
|-
| 10% || 1.07 || align=center|~1 || dilute sulfuric acid
|-
| 29–32% || 1.25–1.28 || align=center|4.2–5 || battery acid<br />(used in [[Voltaic_cell#Lead-acid_cell|lead–acid batteries]])
|-
| 62–70% || 1.52–1.60 || align=center|9.6–11.5 || chamber acid<br />fertilizer acid
|-
| 78–80% || 1.70–1.73 || align=center|13.5–14 || tower acid<br />Glover acid
|-
| 98% || 1.83 || align=center|~18 ||'''Azeotropic''' concentrated sulfuric acid
|}
===Molarity===
In order to get a feel for how much sulfuric acid you have in your water, add a vast excess of [[magnesium carbonate]]. Magnesium carbonate is sparing soluble (0.1g/L) in water, but will react with [[sulfuric acid]] to produce '''magnesium sulfate''', which is quite soluble. You may add more (distilled) water to assure yourself that all the magnesium sulfate is dissolved, but this should not be necessary. Evaporate and weigh the magnesium sulfate, calculate the moles of sulfuric acid in the original solution.
# Place dilute [[sulfuric acid]] of unknown strength in a container
# Add an equal mass of water to the acid
# Add an excess of magnesium carbonate
#: {{#Chem: H2SO4(aq) + MgCO3(s) = H2O + CO2(g) + MgSO4(aq)}}
# Filter
# The residue is magnesium carbonate. Recycle.
# Evaporate the filtrate (magnesium sulfate)
# Weigh the filtrate
# Multiply the mass (in grams) by {{e|4.06|-3}} to get moles of {{#Chem: H2SO4}} in the original solution. (256.366g/mol magnesium sulfate heptahydrate, normal at SPRT)
==Storage==
* Sulfuric acid does not dissolve [[silicon dioxide]], so '''glass''' or [[quartz]] containers are recommended.
* Sulfuric acid does not dissolve [[lead]], so it too can be used as a container.
* While sulfuric acid does not dissolve [[copper]], it does dissolve copper oxides, so copper is probably not a good choice.
* Sulfuric acid is strongly, even dangerously, hygroscopic and will absorb water (and other detritus) directly from the air, so a good seal on the container is recommended.
==Disposal==
* Combining sulfuric acid with almost any copper (II) salt (such as '''copper carbonate''' or '''copper hydroxide'''  will result in [[copper sulfate]], which is GRAS and occurs naturally; other predictable side products  ([[carbon dioxide]], [[water]], [[hydrogen chloride]], etc)
: {{#Chem: Cu(OH)2 + H2SO4 = CuSO4 + 2 H2O // copper hydroxide }}
: {{#Chem: Cu2CO3(OH)2 + 2 H2SO4 = 2 CuSO4 + 3 H2O + CO2 //copper carbonate }}
: {{#Chem: CuCl2 + H2SO4 = CuSO4 + 2HCl //copper chloride }}
* Combining sulfuric acid with almost any calcium salts will create [[calcium sulfate|gypsum]], a naturally occurring mineral and listed as GRAS.

==See Also==
* [[Chamber process|The Chamber Process]]
* {{cite pub|publication=Manual of Chemical Technology|title=Sulfuric Acid|last1=von Wagner|first1=Rudolf||year=1892|publisher=J &amp; A Churchill, London|url=https://books.google.com/books?id=7KWEAAAAIAAJ&pg=PA262|courtesy=Hathi Trust}}
* {{Cite pub|url=http://books.google.com/books?id=PgUC2nH-h64C&pg=PA221&lpg=PA221#v=onepage&q&f=false|courtesy=Google Books|publication=Handbook of Commercial Catalysts|title=Ch 15 Oxidation (Inorganic)|pages=221}}
* {{cite pub|title=Sulfuric Acid|publication=Cooley's Cyclopædia of Practical Receipts and Collateral Information in the Arts, Manufactures, Professions, and Trades, Including Medicine, Pharmacy, and Domestic Economy: Designed as a Comprehensive Supplement to the Pharmacopœia and General Book of Reference for the Manufacturer, Tradesman, Amateur, and Heads of Families|vol=2|first1=Arnold James|last1=Cooley|year=1897|pages=1592|publisher=J. & A. Churchill|url=https://books.google.com/books?id=3fxAAQAAMAAJ&pg=PA1592}}
* {{cite pub
|title=Manganese(II) catalyzed sulfur dioxide oxidation in aqueous solution at environmental concentrations
|first1=Takashi
|last1=Ibusuki
|first2=H.M.
|last2=Barnes
|doi=10.1016/0004-6981(84)90237-3
|publication=Atmospheric Environment
|volume=18
|issue=1
|year=1984
|pages=145-151
}}
* [[Mineral acid intraconversion]]

==References==
<references/>
[[Category:Drying Agents]]