Reactions of liquid Sulfur dioxide PDF

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Sulfur dioxide (SO2) Definition: Sulphur dioxide or sulphur dioxide (British English) is the chemical compound with the formula SO2 It is a toxic gas responsible for the smell of burnt matches. It is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of fossil fuels contaminated with sulphur compounds. OR A colourless, non-flammable, water-soluble, suffocating gas, SO2, formed when sulphur burns: used chiefly in the manufacture of chemicals such as sulphuric acid, in preserving fruits and vegetables, and in bleaching, disinfecting, and fumigating.

Chemical composition of Sulphur dioxide: Sulphur dioxide is a bent molecule with polar covalent bonds between one sulphur atom and two oxygen atoms. The chemical formula is SO2. It is a step toward converting sulphur, oxygen, and water into sulphuric acid. Free oxygen molecules combine with sulphur dioxide given off by the oxidation of sulphur-containing materials to form sulphur trioxide (SO3). This molecule is ideally set up to absorb water and become sulphuric acid (H2 SO4), which is also the primary industrial use for sulphur dioxide.

Occurrence Occurring in nature in volcanic gases and in solution in the waters of some warm springs, sulfur dioxide usually is prepared industrially by the burning in air or oxygen of sulfur or such compounds of sulfur as iron pyrite or copper pyrite. Large quantities of sulfur dioxide are formed in the combustion of sulfur-containing fuels. In the atmosphere it can combine with water vapor to form sulfuric acid, a major component of acid rain. 1 | Page

History Sulphur dioxide has a number of important uses. It has been used as fumigant since ancient times. In the Odyssey, Homer describes the burning of sulphur (formation of SO2) as a way that homes were ‘fumigated’. In the second half of the 20th century, measures to control acid rain were widely adopted. Sulfur dioxide is a precursor of the trioxide (SO3) used to make sulfuric acid. In the laboratory the gas may be prepared by reducing sulfuric acid (H2SO4) to sulfurous acid (H2SO3), which decomposes into water and sulfur dioxide, or by treating sulfites (salts of sulfurous acid) with strong acids, such as hydrochloric acid, again forming sulfurous acid.

Physical properties of Sulphur dioxide Sulphur dioxide (SO2) is a colorless, non-inflammable and toxic gas. It has a very pungent smell. Its odor resembles smolders sulphur. It is highly soluble in water. SO2 can be easily liquefied. It can be liquefied under moderate pressures at room temperatures; the liquid freezes at −73° C (−99.4° F) and boils at −10° C (14° F) under atmospheric pressure.  It is one of the most straightforward gases to melt. This is because it consolidates at room temperature under a pressure of 2 atm. Some Physical properties of sulphur dioxide are shown below in table.     

Property Molecular weight

Value 64.06 −75.5 °C Melting point Latent heat of fusion (at 115.6 J/g m.p) Dynamic viscosity at 0 °C 368 Pa/s Density at −10 °C 1.46 g/cm3 Critical density 0.525 g/cm3 Critical pressure 78.8 bar Critical temperature 157.5 °C Boiling point −10 °C Molar volume (0 °C, 1013 21.9 l/mol mb)

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Chemical Properties of Sulphur Dioxide 

It is an acidic oxide.



It is readily dissolvable in water.

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It can dissolve other compound because of its non-aqueous solvent nature.

Structure of sulphur dioxide (so2): 

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The sulphur Dioxide which is also known as Sulphur Dioxide is the entity of a bond between Sulphur and Oxygen atoms. The molecular shape of SO2 is same as the molecular geometry of Carbon Dioxide (CO2). Now, if we want to check the exact molecular shape of SO2, then we should understand the positions and number of electrons distributed between Sulphur and Oxygen. In the outer level, Sulphur has six electrons, and the Oxygen has four of them among which one electron is used for each bond. So total number of ten electrons in five pairs. To make bonds, four pairs are needed, so one pair remains alone. The two double bonds use two pairs each and form as a single unit. As the single lone pair not counted in the shape’s description, we can conclude that the molecular shape of SO2 is V-Shaped or Bent. The SO2 has a bond angle of 120-degree. One single atom of Sulphur is bonded with two atoms of Oxygen covalently. It causes a repulsion of electron pairs to form the 120degree angle. The hybridization of so2 will be SP2. To calculate the hybridization we have to check the total number of atoms which are attached with sulphur and the lone pair of electrons. Sulphur has two atoms and one lone pair of electron so the hybridization will be SP3 hybridization.

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Reactions of sulphur dioxide (SO2): 1.

Precipitation reaction:

In these type of reaction precipitates are formed in the solution. Precipitation defined as the creation of a solid from a solution. When the reaction occurs in a liquid solution, the solid formed is called the 'precipitate'. The chemical that causes the solid to form is called the 'precipitant'. OR A chemical reaction in which a cation and anion combine to form an insoluble anionic solid, the reaction is known as precipitation reaction.

Precipitation reactions for liquid sulphur dioxide: A large number of precipitation reactions can be carried out in liquid sulphur dioxide so2 due to solubility relationships. The precipitation of several compounds in liquid sulphur dioxide can be carried out by treating soluble compound in so2.

Reaction number 1: When silver acetate (2CH3COOAg) which is an inorganic compound white crystalline solid reacts with Thionyl chloride, which is an moderately volatile colourless liquid with an unpleasant acrid odour in the presence of liquid sulphur dioxide solution then the precipitate of silver chloride (2AgCl) and Thiodiacetic Acid Sulfoxide will form.

Reaction number 2: When potassium iodide (KI) which is prepared by reacting iodine with a hot solution of potassium hydroxide reacts with Thionyl chloride, which is a 5 | Page

colourless liquid in the presence of liquid sulphur dioxide then the precipitate of potassium chloride will form. Because the potassium chloride is soluble in water, that’s why we used liquid sulphur dioxide as a solvent to form the precipitate of potassium chloride and another product the silicon dioxide will form.

Reaction number 3: If we react Antimony trichloride (sbcl3) is the chemical compound with the formula SbCl3 which is soft colourless solid with a pungent odour with lithium iodide (LiI) in liquid sulphur dioxide then it will form the precipitate of Antimony triiodide (SBI3) and lithium chloride will be formed.

Reaction number 4: If we react the lead fluoride (PbF2) which is a white solid it exists as both an orthorhombic and cubic forms with lithium sulphate (Li2So4) which is a white inorganic salt in liquid sulphur dioxide then it will form the precipitate of lead sulphate (PbSO4) which is a white solid, which appears white in microcrystalline form. It is also known as fast white, milk white, sulfuric acid lead salt or anglesite, and another product lithium fluoride (LiF) will formed.

Reaction number 5: The Aluminium chloride (AlCl3) which is a pure compound formed by the exothermic reaction of metallic Aluminium and hydrogen chloride (HCl) in the temperature range of 650-750 °C reacts with sodium iodide (3NaI) in the presence of liquid Sulphur dioxide it will leads to the formation of precipitate of sodium chloride 3NaCl a salt which is soluble in water and insoluble in liquid sulphur dioxide and the other product will be Al I3.

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Reaction number 6: In this reaction the reactant barium iodide (BaI2) which is an inorganic compound with the formula BaI₂ exists as an anhydrous and a hydrate, both of which are white solids reacts with another reactant zinc salt Zn2 (CNS) 2. The Zinc salts are an entire class of compounds where zinc molecules are bound to other elements to create the aforementioned neutral compound. This reaction will takes place in the presence of liquid sulphur dioxide then the barium salt will formed in the precipitated form Like most other barium salts, it is white, toxic, and imparts a yellow-green coloration to a flame and the other product will be zinc iodide (ZnI2).

Redox reaction Here is a specific type of chemical reaction called oxidation-reduction reactions. In these reactions, electrons are transferred from one reactant to another. So, simply put, electrons are lost from one substance and gained by another. Reduction: A process in which an atom gains an electron and therefore decreases (or reduces its oxidation number). Basically the positive character of the species is reduced. Oxidation: A process in which an atom loses an electron and therefore increases its oxidation number. In other words, the positive character of the species is increased. Example

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Redox reaction of liquid Sulphur dioxide Many reactions are known where gaseous sulphur dioxide (so 2) behaves both as oxidizing and as reducing agent. But sulphur dioxide in liquid state does not have any marked reducing or oxidizing tendency and only acts as a medium for many redox reactions. .

Reactions 1. Sulphite in liquid sulphur dioxide reduces iodine to iodide Liq. so2 I2

+

2R2 So3

R2 so4 +2RI

+ so2

In this reaction Sulphite ion (SO₃²⁻) reduces iodine in to iodide ion and then converted itself in to sulphate ion (SO₄²- ).In reactant form iodine whose oxidation state is zero (0) while in product form in iodide ion its oxidation state is -1. Here oxidation state decreases from 0 to -1 so iodine reduces to iodide ion. 2. Ferric chloride in liquid sulphur dioxide oxidized iodide ion to iodine Liq. so2 2Fecl3 +2KI 2Fecl2 + 2kcl+ I2 In this reaction ferric chloride (Fecl 3) oxidized potassium iodide (KI) in to iodine (I2) and itself reduces in to ferrous chloride (Fecl2).In reactant form iodide ion whose oxidation state is zero (-1) while in product form in iodine its oxidation state is zero (0). Here oxidation state increases from -1 to 0 so iodide ion oxidized in to iodine. 3. Antimony pentachloride in the presence of liquid sulphur dioxide oxidized potassium iodide (KI) in to iodine Liq. so2 3Sbcl5 +6KI

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2k3 [Sbcl6] + Sbcl3 + 3I2

In this reaction antimony pentachloride (sbcl5) in the presence of liquid sulphur dioxide (so2) oxidized potassium iodide (KI) in to iodine and itself reduces in to Antimony trichloride (sbcl3). In reactant form iodide ion whose oxidation state is zero (-1) while in product form in iodine its oxidation state is zero (0). Here oxidation state increases from -1 to 0 so iodide ion oxidized in to iodine.

Acid-Base reaction or Neutralization reaction Any substance which gives SO2+ ions would behave as an acid, where as any substance which gives SO3 2- would behave as a base in liquid SO2. e.g. SOCl2 and SOBr2 behave as acids in liquid SO2 while Na2SO3 would behave as a base.

Some acid-base reactions in liquid SO2 are SOCl2 + Cs2SO3

Liq.So2

2CsCl

+

2SO2

Sulfuryl chloride is an inorganic compound with the formula SOCl2. At room temperature, it is a colorless liquid with a pungent odor. Sulfuryl chloride is not found in nature, as can be inferred from its rapid hydrolysis.

SO (SCN)

2

+ K2SO3

Liq.SO2

2K (SCN) +

2SO2

Thiocyanate (also known as rhodanide) is the anion [SCN] −. It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Organic compounds containing the functional group SCN are also called thiocyanates. Mercury (II) thiocyanate was formerly used in pyrotechnics. SOBr2 + [N (CH3)4]2SO3

Liq.SO2

2[N (CH3)4] Br + 2SO2

Thionyl bromide is the chemical compound SOBr₂. It is less stable and less widely used than its chloride analogue, Thionyl chloride. When it react with 9 | Page

Tetramethylammonium Sulfur trioxide is the coordination compound with the formula [N (CH3)4]2SO3 in the presence of liquid SO2 it give product Tetramethylammonium bromine and Sulfur dioxide. SOCl2 + K2SO3 Acid

Liq.SO2

2KCl + 2SO2

Base

Potassium sulfite is the inorganic compound with the formula K2SO3. It is the salt of potassium cation and sulfite anion. It is a white solid that is highly soluble in water. When it react with Sulfuryl chloride is an inorganic compound with the formula SOCl2. At room temperature, it is a colorless liquid with a pungent odor. Sulfuryl chloride is not found in nature, in the presence of liq. SO2 it give product potassium chloride and sulfur dioxide.

Amphoterism The ability of a chemical to behave as both an acid and a base is called Amphoterism, and this type of substance is known as an amphoteric substance. Generally, such a substance acts as an acid in the presence of a base, and it acts as a base in the presence of an acid. 

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Amphoteric substances include water, amino acids, and proteins. Many metals (such as zinc, tin, lead, aluminum, and beryllium) and most metalloids have amphoteric oxides. It comes from the Greek word ‘amphoteroi’ which means ‘both’. The chemicals involved in the reaction dictate whether an amphoteric molecule will act as a base or acid. Since all amphoteric compounds must be able to donate a proton, they all contain a hydrogen atom. Some examples are water and amino acids. It applies to acids and bases according to the Bronsted-Lowry theory and Lewis theory.

For Example: A water molecule can even act as an amphoteric molecule in a sample of pure water. Roughly 6 in 10 8 water molecules undergo the following reaction: 10 | P a g e

H2O (l) + H2O (l)

→ H3O+ (aq) + OH− (aq)

This reaction is called autoionisation. It occurs in every solution, no matter if the sample of pure or it is part of a solution.

Reaction no 1: Zinc chloride and potassium sulfite is amphoteric substance. Its behavior as an acid or base depends on the pH of the solution. In an acidic solution, it reacts as a base; in a basic solution, it reacts as an acid. The chemical reactions can be written as: This property can be used to separate different cations. Zinc (II) chloride, also known as butter of zinc, is an inorganic salt very soluble in water and other liquid medium. When zinc chloride is react with Potassium sulfite is an inorganic compound. It is the salt of potassium cation and sulfite anion. These 2 salts react in the medium of sulfur dioxide and make Zinc Sulfite + Potassium Chloride.

Reaction no 2: Zinc sulfide (or zinc sulphide) is an inorganic compound, it mainly occurs as the mineral sphalerite. When it react with another Potassium sulfite is the inorganic compound with the formula K2SO3. It is the salt of potassium cation and sulfite anion. It is a white solid that is highly soluble in water. These 2 compound react in the presence of medium liquid Sulfur dioxide is a versatile inert solvent widely used for dissolving highly oxidizing salts. After, that we get product potassium disulfurtrioxide zincate (II).

Reaction no 3: Aluminum Sulfite is an Ionic compounds are generated by the electrostatic attraction between oppositely charged metals and polyatomic ions. Metallic elements lose electrons to become positively charged ions. Polyatomic ions are two or more atoms chemically combined that have an overall net electric charge. In this Reaction it react with potassium sulfide in the presence of

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versatile inert solvent as a medium, and make product potassium trialuminate sulfate.

Reactions no 4: Aluminium chloride (AlCl3), also known as Aluminium trichloride, are white solids, but samples are often contaminated with iron (III) chloride, giving a yellow color reacts with Potassium sulfite is the inorganic compound with the formula K2SO3. It is the salt of potassium cation and sulfite anion. It is a white solid that is highly soluble in water and non-aqueous solvents. When it react in the presence of versatile medium liquid sulfur dioxide and this reaction gives the product Potassium chloride and Aluminium sulfate.

Reaction no 5: When Aluminium chloride reacts with tetramethyl ammonium sulfide in the presence of medium liquid sulfur dioxide we, get Aluminium sulfide Gelatinous precipitate when, we add more base to this precipitate like addition of tetramethyl ammonium sulfide then, we get a soluble complex. When this soluble complex reacts with acid Thionyl chloride, because in liquid sulfur dioxide thinly chloride is an acid then we get again Aluminium sulfide precipitate.

Cl + 6SO2 Gelatinous Precipitate

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Reaction no 6: In this reaction [I3] + and [I5] + have been isolated as [AsF6] - salts from the reactions of AsF5 and I2 in liquid SO2, the product depending on the molar ratio of the reactants. Reactions of selenium with AsF5 (at 350 K) or SbF5 (at 250 K) in liquid SO2 have yielded the salts [Se4] [AsF6]2 and [Se] [SbF6]2 respectively.

Solvolysis reaction or Solvolytic reaction: Solvolysis, a chemical reaction in which the solvent, such as water or alcohol, is one of the reagents and is present in great excess of that required for the reaction. Solvolytic reactions are usually substitution reactions— i.e., reactions in which an atom or a group of atoms in a molecule is replaced by another atom or group of atoms. The solvents act as or produce electronrich atoms or groups of atoms (nucleophiles) that displace an atom or group in the substrate molecule. At high temperatures or in the presence of strong bases, some solvents act as eliminating agents, producing alkenes from alkyl halides. It is common practice to name Solvolysis reactions after the specific solvent, such as “hydrolysis” when water is the reagent.

Solvolysis reaction or Solvolytic reaction in liquid SO2: The Solvolysis is derived from two words “solvo” means solvent and “lysis” means breakdown of solvents. The reaction in which the solvents molecule reacts with the solute in such a way that the solvent molecule split up into two parts ,one or both of which get attached to the solute molecule or ion are called Solvolytic reaction.

Reactions: Only a limited no. of salts e.g. certain covalent binary halides and ammonium acetate undergo Solvolysis in liquid sulfur dioxide. For example: pcl5, UCL6, WCL6, Zn (C2 H5) etc. 13 | P a g e

Solvolytic reaction in liquid sulfur dioxide are not as common as they are in other solvents such as ammonia. Some of the reactions are given here.

Reaction No 1:

This is the reaction of ammonium acetate with liquid Sulfur dioxide. The ammonium acetate get solvolyzed as it forms the ammonium sulphite and thionyle acetate .In this case the sulfur dioxide is being split into thionyle and sulphide, the thionyle part goes with the acetate molecule and sulphite parts goes with the ammonium ion.

Reaction No 2:

Certain covalent halides also undergoes solvolyzed in liquid sulfur dioxide .when phosphorus pentachloride react with two molecules of sulfur dioxide, it produces the phosphoryl chloride and Thionyl chloride.

Reactions No 3:

If we may to react uranium hexachloride with liquid sulphur dioxide so it produce Oxy chloride of uranium and Thionyl chloride.

Reaction No 4:

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When diethyl zinc being ...