Chapter 12: Nitrogen and Sulfur

The bond present in nitrogen molecule has a bond enthalpy of +944 kJmol-1. High energy is required to break this bond to form new bonds, making N2 very unreactive. The second reason for its lack of reactivity is the nonpolarity of its bond. Both the atoms are the same having zero electronegativity difference. This causes equal sharing of the three bonded electrons between the two atoms making the bond nonpolar

In industrial processes, nitrogen is typically obtained by cooling air until it becomes a liquid In laboratory settings, nitrogen can be generated by slowly heating a solution of ammonium nitrite. 2(g) + H, 0(1) NH,NO 2(29)

See Q.1 from theory

→ 2NO (g) N2(g) + 02(g) 2N0(B) + 02(g) 2N02(g) fred hv → NO NO 2(g) (8) + 0(8) 8) + 02(g) → 03(8) RCH = RCH (g) + 03(g) - the construction and What is

See Q.3 from theory. As shown in the structure two oxygen atoms have double bonds with sulfur while two have single double bonds, acidic bond have less bond length than single bond and hence greater bind energy, therefore two different bond lengths are observed for sulfur and oxygen bond in sulfuric acid.

Construction A catalytic converter is a ceramic or metallic monolith with a honeycomb-like structure. Its inner channels have a layer of alumina to ared. Noble provide a high surface expensive metals such as Pt (Platinum), Pd and Rh (Rhodium) are (Palladium), dispersed on the alumina. Working These metals catalyze three redox reactions to remove the half harmful exhaust gases. The three-way converter converts harmful CO, NO, and hydrocarbons into CO2, N2, and water. These precious metals can also be recycled. (Reduction) Pt / Rh → N2(g) + 2CO2(g) 2NO (g) + 2CO (g) (Oxidation) Pt / Pd 2CO (8) + 02(g) •→ 2CO2(g) Pt / Pd → 4C0 2(g) + 4H, 0(g 2C, H4 + 602(g)

See Q.8 from theory.

At room temperature it occurs as octasulfur which is quite unreactive and has a high bond strength S S • S Cyclo-octasulfur, (Ss) crown molecule most stable are the

See Q.9 from theory.

At pH = 0 (strongly acidic) Most stable oxidation state: +b • • Common sulfur species: • H2SO4 • At pH = 14 (strongly acidic) • Most stable oxidation state: -2 • Common sulfur species: • S2- HS- •

SF4 and SF6. Sulfur hexafluoride (SF6) is a gas and is very unreactive. It is used as an insulator gas in electric devices. Sulfur readily, reacts with Cl to form S2C12 (yellow liquid) which further reacts with Cl to form SCl (red liquid). → SE6(B) S(s) + 352(g) →S, C12(1) 25(s) + C12(g) → 2SC12(1) S, C12(0) + 5(8) Draw the structures of cyclo-

Sulphur is used as a cross linker for the molecular rubber chains. This is called and it vulcanization improves the strength of rubber cross S-S linkage between polymer chains.

Gun powder is a coarse blend of 75% potassium nitrate (KNO3), 15% wood charcoal, and 10% sulfur. Charcoal carbon is the main fuel, nitrate is the oxidizer and sulfur is the additional fuel that burns the powder faster. The following reaction in burning takes place: 10KNO3(s) + 35(s) + 8C (s) - 2K, CO3(s) + 3K,SO 4(8) + 6CO 2(g) + 5N 2(g) is the importance of

Disulfide bridges are crucial in organic molecules stability of large including biomolecules such as proteins. They provide structural integrity to the molecule. Sulfur dyes are synthesized by the process of thionation or sulfurization of organic compounds that contain nitro or amino groups. These compounds contain sulfur linkages. They generally give black, brown, khaki, blue, and green colours. self-ionization Write down

It self-ionizes or undergoes autoprotolysis as follows. K. = 2.7 × 10" The equilibrium constant value is greater than that of water which makes it to be used as a non-aqueous protic solvent. Sulphuric acid is a strong acid as shown by its pKal value: • + HSO- HO!+ 4 (aq) (aq) H, SO 4(a9) + H2O (pKa, =-2) But hydrogen sulfate (HSO") is a tar weaker acid due to a positive plaz value: 4(aq) : H, O*, + SO*- (pKa2 = 1.92)

Concentrated sulphuric acid is a powerful dehydrating agent that removes water from many substances such as sucrose, starch, wood, and paper to produce carbon, steam, and heat. • Dehydration of table sugar 4(aq) 12C(g) + 1 1H, 0(g) + H,SO e a black porous carbon mass called carbon snake protrudes out of the apparatus. • Dehydration of alcohol It also dehydrates ethyl alcohol to ethene or ethoxyethane depending upon the reaction conditions. V205 catalyze the

Purified SO2 and air, preheated at 420°C- 450°C, are fed to the first converter stage of the contact tower at 1-2 atm SLO BASED SHORT QUESTION ANSWERS

Mixing SOs with water is not feasible because the reaction is extremely exothermic and acidic vapor or mist is produced rather than a liquid solution. Mainly, sulfur trioxide is dissolved in recalculating hot 98.5% sulphuric acid. The term fuming sulphuric acid or oleum is used for the mixtures of sulfur trioxide with 100 percent sulphuric acid. nitrogen atom in ammonia utilizes this lone pair of electrons to form ammonium, this ion adopts a tetrahedral shape in which all the bonds are of equal length and strength, H H H H

Natural Sources Natural sources include lightning, volcanos, soil forest fires, decay, biological microorganisms, oceans, etc. • NO is produced when N2 and O2 in the air react during lightning • It is produced by microorganism using air N2 Anthropogenic (Man-made) Sources • The main anthropogenic sources of NOx are the combustion of fossil fuels in vehicles and power plants. • Other sources include chemical plants, biomass burning, welding, etc

Nitrogen is a significant component of the air, known for its low reactivity due to its-small size, symmetrical electronic cloud, and nonpolar triple bond With an electronic configuration of 1s 2s 2p? , nitrogen requires three electrons to complete its octet, forming à triple bond by sharing three electrons with another nitrogen atom. Catalytic converter reaction in reduction

Ammonia NH3 / NH" is converted into nitrite (NO,) and nitrate (NO,). Nitrifying bacteria aerobic conditions, pH 6.5 - 8.0, optimum temperature 20 °C-30°C

Iron pyrite often called "Fool's gold" because of its gold like appearance. Many people considered it gold when it is mined. It's formula is FeS2.

pH: In general, under acidic conditions, reduced forms (like H2S, -2 oxidation state) are more stable, while under basic or neutral conditions, oxidized forms (like SO*, +6 oxidation state) become more stable in water Thermodynamics and kinetics: Although sulfur (+6), as in SO3, is thermodynamically the most stable kinetic limitations can prevent it from forming readily at standard temperatures, making sulfur (+4), as in SO2, the more frequent form

Sulfuric acid has melting point of 10°C and boiling point of 290°C between the range of boiling and melting point any substance will be liquid state therefore sulfuric acid is liquid at room temperature. As it is a strongly polar molecule it has a high boiling point and low vapor pressure does NOz catalyze the

It oxidizes SO2 to SO3 in the process and itself is reduced to NO NO reacts with O2 to get into NO2 state 250, + 2N0, → 250, + 2NO 2N0 + 0½ → NO, NO2 acts as a catalyst in tis reaction industrially catalyst like vanadium pentoxide is used.

Because high temperature increases the rate of reaction but lowers the yield while low temperature has high yield but the reaction is very slow Therefore high temperature and catalysts are used and yield is increased by adding oxygen into the reaction chamber. How is catalyst regenerated in

Sulphuric acid is a strong acid as shown by its pKal value: pka=-2) But hydrogensulfate (HSO+ ) is a far weaker acid due to a positive pKa value (pK 2=1.92) HSO 4(ag) + H, 0(.) H, 0(ag) + SO 4(ag)

Sulfur reacts directly with F2 to form SF4 and SF6. Sulfur hexafluoride (SF6) is a gas and is very unreactive. It is used as an insulator gas in electric devices. Sulfur readily reacts with Cl to form S2 Cl (yellow liquid) which further reacts with Cl to form SCl (red liquid). S(s) + 352(g) →→SE6(8) 25(g) + C/2(g) →→S,CL21) Cl 2(g) + S, Cl 2(0) 25Cl 2(e)