Q: Define "BOD". Give its possible values of clean water and municipal water. (2 Marks)

Chemistry Environmental Chemistry, Organic Chemistry 2 Marks Questions Q: Define "COD". How is it determined? A: The amount of oxygen required to oxidise organic material present in polluted water. It is determined with acidified (50% H2SO4) K2Cr2O7. Q: Define "Sink" and "Receptor". A: Sink: The medium which is not only effected by the pollutant but also remains there. Trees are sinks of CO2. ★ Receptor: The medium which is badly effected by the pollutant. Eyes are receptors during traffic jam. Q: What is "Threshold Limit Value" (TLV)? A: The permissible level of a toxic pollutant in atmosphere where a healthy person works in that atmosphere for 8 hours per day without any adverse effect. Q: What is "green house effect"? A: The phenomenon of gradual rise of temperature of earth due to absorption of infrared radiation of sun rays by the gases like CO2, CH4, CFCs and O3. Q: Which oxides cause acid rains? What is its pH value? A: Acid rains are caused by the oxides NO2 and SO2 (due to formation of H2SO4, HNO3) when they reacts with O2 & H2O. pH of acid rain water is below 5.6. Q: Name two adverse effects caused by acid rains. A: Decrease of fertility of soil as acid rains dissolve nutrients and washes away. ★ Damage of historical monuments like Taj Mahal. Q: What is "PAN''? What effect is caused by it? A: When O3 & NO2 react with unburnt hydrocarbons to form formaldehyde, acrolein and PAN (Peroxy Acetyl Nitrate). PAN causes irritation of eyes. H2C = CH CH O + 2O3 → H3C COOO NO2 (Acrolein) (PAN) Q: What is "ozone hole"? Where was it first observed?

4 Marks Questions Q: Explain a) Position isomerism and b) Functional isomerism with one example each. A: a) The isomerism that arises due to change in the position of substituent atom or functional group or multiple bond on the carbon skeleton. Eg: Propan - l - ol & Propan - 2 - ol b) The isomerism that arises when 2 or more compounds having same molecular formula but different functional groups. Eg: C2H5OH & CH3O CH3 Q: Discuss "Markownikov's rule" and "Kharasch effect". A: Markownikov's rule: The −ve part of the adding reagent gets attached to that carbon atom of the double bond which has least no. of H atoms. H I H ⎯ C ⎯ C = C ⎯ H + H+ − Br − ⎯→ I I I H H H H Br H I I I H ⎯C ⎯C ⎯C ⎯H I I I H H H

A: The amount of oxygen consumed by micro organisms present in polluted water during 5 days at 20°C. A.N.S. Sankara Rao

★ BOD of clean water is 5 PPm, municipal water is 100 to 4,000 PPm.

What is Green Chemistry? A: The depletion of ozone layer present in stratosphere is caused by CFCs. It was first observed over the south pole. Q: What are the harmful effects caused by ozone layer depletion? A: Causes skin cancer & cataract. ★ Damage to fish productivity. ★ Paints & fibres fade faster. ★ Decrease of moisture in soil. Q: What is 'Eutrophication'? A: Drying of lake due to overgrowth & decay of algae and other plants & killing of fish (due to lack of oxygen) due to over nutrition of lake water. Q: What is "Green Chemistry"? A: New branch of Chemistry which helps in reduction in the production & use of harmful pollutants by using existing knowledge of Chemistry and other sciences. Q: Write IUPAC names of the following compounds. a) CH3 I b) H3C ⎯ CH2 ⎯ CH ⎯ C ⎯ CH ⎯ C2H5 I I I CH3 CH3 CH3 A: a) 1, 3 - Buta diene b) 3, 4, 4, 5 - Tetra methyl heptane. Q: Discuss "Lassaigne's test." A: Organic compounds having N, S, halogens are covalent hence which are to be converted into ionic compounds by fusing with sodium metal. ∆ Eg: Na + C + N ⎯→ NaCN Q: Explain the principle of Chromatography. A: The technique in which the mixture of substances is applied on stationary phase (solid or liquid) and a mobile phase (gas or solvent) is allowed to move slowly over the stationary phase. The components are separated from Anti Markownikov's rule (Kharasch effect): In presence of peroxide, the −ve part of the adding reagent gets attached to that carbon atom of the double bond which has more no. of H atoms. H I (C6H5CO)2O2 H ⎯ C ⎯ C = C ⎯ H + H+ ⎯ Br − ⎯⎯⎯⎯→ I I I H H H H H H I I I H ⎯ C ⎯ C ⎯ C ⎯ Br I I I H H H Q: Give two methods of preparation of Benzene. A: C6H6 is formed when sodium benzoate is heated with soda lime (NaOH + CaO) CaO

C6H5 COO Na + Na O H ⎯⎯→ ∆ C6H6 + Na2CO3 ★ C6H6 is formed on distillation of phenol with Zn ∆ C6 H5 O H ⎯→ C6H6 + ZnO + Zn Q: Explain: a) Nitration; b) halogenation; c) sulphonation and d) acylation of benzene. A: a) −NO2 is introduced into C6H6 ring when

one another in pure form. Q: Write the conformations of Ethane.

Q: Name the products A, B, C in the reaction: Br2 AlC. KOH Br2 Ethylene ⎯⎯→ A ⎯⎯⎯⎯→ B ⎯→ C CCl4

H

A: H

H

AlC. KOH

Br2

H

H

A: H2C = CH2 ⎯→ H2 C − CH2 ⎯⎯→ HC ≡ CH −2HBr CCl4 I I (B) Br Br (A)

H H

H

H

H

H H

Eclipsed conformer

Staggered conformer

Q: Name the products A, B, C in the reaction. H2O hot metal AlCl3 CaC2 ⎯⎯→ A ⎯⎯⎯→ B ⎯⎯⎯→ C tube CH3Cl

A: Ca C2 + 2H ⎯ OH ⎯→ C2H2 + Ca(OH)2 (A) hot metal 3 C2H2 ⎯⎯⎯→ C6H6 tube (B)

Br Br I I HC ≡ CH ⎯⎯→ H − C − C − H I I Br Br 2Br2

(C)

A = 1, 2 - dibromo ethane; B = Ethyne; C = 1, 1, 2, 2 - tetra bromo ethane Q: Write E, Z configurations for CHCl = CFBr. A: Cl

Cl

Br C=C

H

–

C=C F

H

Z Configuration

AlCl3 C6H5 ⎯ H + Cl ⎯ CH3 ⎯⎯→ C6H5.CH3 + HCl (C)

A = Acetylene; B = Benzene; C = Toluene Q: What is 'Substitution reaction'? Give one example. A: The reaction in which a group or an atom is replaced by another atom or a group. Anhyd. AlCl3 Eg: C6H5 ⎯ H + Cl ⎯ CH3 ⎯⎯⎯⎯→ C6H5.CH3 + HCl Q: What is "Carcinogenicity"? Name two compounds cause it. A: Cancer producing property by fused benzene rings (3 or more), which are formed due to incomplete combustion of tobacco, coal and petroleum. Eg: 1, 2, - Benzpyrene, 1, 2 - Benzanthracene

heated with nitrating mixture. Conc. H2SO4

C6H5 ⎯ H + HO ⎯ NO2 ⎯⎯⎯⎯→ 323 − 333 K

C6H5.NO2 + H2O b) −Cl is introduced into C6H6 ring when treated with Cl2 in presence of Anhydrous AlCl3.

Anhyd.AlCl3 C6H5− H + Cl − Cl ⎯⎯⎯⎯⎯→ C6H5Cl + HCl c) −SO3H is introduced into C6H6 ring when heated with oleum. ∆ C6H5 ⎯ H + HO ⎯ SO3 H (SO3) ⎯⎯→ C6H5.SO3H + H2O d) −COCH3 is introduced into C6H6 ring when heated with CH3COCl in presence of Anhyd. AlCl3. Anhyd. AlCl3 C6H5 ⎯ H + Cl ⎯ COCH3 ⎯⎯⎯⎯→ C6H5.COCH3 + HCl Q: Explain a) Decarboxylation and b) Kolbe's electrolytic method. A: a) The phenomenon of removal of CO2 from sodium salt of carboxylic is called decarboxylation. It happens when it is heated with soda lime. CaO ∆

CH3 COO Na + NaO H ⎯⎯→ CH4 + Na2CO3

F

Br

E-Configuration

Q: What is ''inductive effect"? A: The displacement of sigma bonded electrons towards more electronegative atom side in saturated organic compound to form polar covalent bond. δδ+ δ+ δ− Eg. CH3 ⎯→⎯ CH2 ⎯→⎯ Cl Q: Name the functional group isomers of C3H6O . A: Propanone 2 (CH3COCH3)

–

Propanal (CH3CH2CHO) Q: What is "Wurtz reaction"? A: The reaction in which alkyl halide reacts with Na in dry ether to give hydrocarbon containing double the no. of carbons present in the alkyl halide. dryether CH3 I + 2Na + I CH3 ⎯⎯⎯⎯→ H3C−CH3 + 2NaI b) An alkane (with even no. of carbons) is formed on electrolysis of aqueous solution of Na or K salt of carboxylic acid. CH3 COO Na

+

HO H

Electrolysis

⎯⎯⎯⎯→

CH3 COO Na HO H C2H6 + 2CO2 + H2 + 2NaOH Q: Explain a) Ozonolysis; b) Oxidation; c) Addition of H2SO4 and d) Polymerisation of Ethylene. A: a) Addition of O3 to ethylene forms ethylene ozonide. Which on hydrolysis gives methanol. Zn

C2H4 + O3 ⎯→ C2H4 .O3 ⎯⎯→ H2O

2HCHO + H2O2 b) C2H4 on oxidation with Baeyer's reagent (cold, dilute, alkaline KMnO4) to give glycol. CH2 + (O) + H CH2 − OH 273 K ⏐⏐ ⏐ ⎯⎯⎯⎯⎯→ ⏐ OH dil alkaline MnO4 CH2 − OH CH2 c) Addition of cold conc. H2SO4 to C2H4 gives ethyl hydrogen sulphate. 273 K

C2H4 + H−HSO4 ⎯⎯→ C2H5 −HSO4 d) Ethene on polymerisation at high pressure & temperature in presence of catalyst gives polyethene. High P&T

n (H2C = CH2) ⎯⎯⎯→ ⎯( CH2 − CH2 ⎯ ) n Catalyst

Polyethene