2011 - International Year of Chemistry

Remember 2011 is international year of Chemistry

Copernicium - Atomic Number 112

The heaviest chemical element with the atomic number 112 has officially been named Copernicium. Its symbol is Cn. It was discoverd in Germany on 9th February 1996 by an international team of scientists.

The Recommendations will be published in the March issue of the IUPAC journal Pure and Applied Chemistry and is available online at Pure Appl. Chem., 2010, Vol. 82, No. 3, pp. pp 753-755 (doi: 10.1351/PAC-REC-09-08-20).

Reference

http://www.iupac.org/web/nt/2010-02-20_112_Copernicium

Press Release Dated 19 February 2010.

http://www.iupac.org/news/archives/2010/Element_112_Press_Release.pdf

National Science Day - 28th February

Today is National Science Day of India.

Learn your science subjects with more commitment. Try to understand things in depth. As an engineer, you need to find new solutions based on existing scientific as well as new theories.

http://knol.google.com/k/narayana-rao-k-v-s-s/national-science-day-india-28th-february/2utb2lsm2k7a/2346#

You need to keep interest in science even after you become an engineer.

Polymers and Their Monomers

Polymer - Monomers


Homopolymers (Only one monomer)

Cellulose – Glucose
Natural rubber – Isoprene (2-metyl-1, 3-butadiene)

Neoprene - Chloroprene
Nylon-6 - caprolactum

Polyacrylonytrile (PAN) or Orlon – Vinyl cyanide (acrylonitrile)
Polyethelene - Ethylene (Ethene)
(Popularly polythene)
Polyethyl acrylate (PEA) - ethyl acrylate
Polymethyl methacrylate (PMMA) – Methyl methacrylate
Polymonochlorotrifluoroethylene (PCTFE) - chlorotri-fluoroehtylene
Polypropylene – Propylene
Polystyrene or Styron – styrene
Polytetrafluoroethylene (Teflon or PTFE) - tetrafluoroethylene
Polyvinyl chloride – Vinyl chloride
Proteins - Alpha-Amino acids

Starch - Glucose


Copolymers (Two different monomers)

Bakelyte (Phenol formaldehyde resin) - Phenol and Formaldehyde
Buna-S - 1,3-butadiene and styrene
Dacron (Polyster) - Terephthalic acid and ethylene glycol
Glyptal - ethylene glycol and phthalic acid
Melamine polymer (Melamine formaldehyde) - Melamine and fromaldyhyde
Nylon-66 - Hexamethylenediamine and adipic acid
Saran - vinyl choride and vinylidene chloride
Styrene-butadiene rubber - styrene and 1,3-butadiene
Thiokol - 1,2 dichlorlethene (ethylene dichloride) and sodium polysulphide
Terylene - ethylene glycol and terephthalic acid

Difference Between a Metal and Polymer

In the chapter in polymers, it is explained that polymers are compounds of very high molecular masses formed by the combination of a large number of simple molecules. Simple example of a polymer is polyethelene. This polymer is formed by the compound formation between molecules of ethelene. The molecules of ethylene in the case of formation of polymer are referred to as monomers.

But what is the difference between a metal and polymer?

Metal

At a molecular level, the basic units that make up a metallic structure are relatively small and uniform in size. Consequently, they readily arrange into a structure that is very regular and predictable. Material scientists call these structures as crystalline solids.


Polymer

The smallest unit in a polymeric material is a very large molecule with an extended chain shape. (Remember linear chains, branched chains and cross linked chains). Even the smallest polymer molecule will be about 50 times more massive than the heaviest naturally occurring unit in a metallic structure. These polymer molecules can twist, turn, fold, and entangle in almost unlimited variations (Remember the point regarding straightening of chains due to stretching). In addition, not all of these molecules are of the same size. The smallest molecule in any random sample of plastic is often a thousand times smaller than the largest, which increases the possibilities for local variation in the structure of a material.


In a metal there ionic forces between free flowing electrons and the positive charged nucleuses that hold the metal together. In a polymer there are covalent bonds between molecules of various sizes, with each molecule being polymer of number of monomers.

Top Down and Bottom Up Learning

Top Down learning is studying a lesson first and then solving problems. Most of the time you are doing it in all complex subjects and topics.

Bottom Up learning is trying to solve a problem and finding new issues which are to be used in solving the problem. Everybody needs to engage in bottom up learning also. Top down is not sufficient.

Solve all problems of past JEE examinations at least five years 2009, 2008,2007,2006 and 2005 and engage in bottom up learning.

Now it is the time.

Chemistry Specific Topics Tested in IIT JEE 2009 Paper II

1. Migration of H and CH3 groups in intermediate reaction compound when a positive carbon ion is present.


Migrating nature of H is more than CH3.

2. The spin only magnetic moment value


The spin only magnetic moment value (in Bohr magneton units) of Cr(CO)6 is -
(A) 0 (B) 2.84
(C) 4.90 (D) 5.92

Answer A


CO is a strong field ligand.

3. Stability order of resonance structures


The species with incomplete octet are less stable.

4. k = Ae^(–Ea/RT)


For a first order reaction A→P, the temperature (T) dependent rate constant(k) was found to follow the equation logk = – (2000)(1/T) + 6.0
The pre-exponential factor A and the activation energy E_aa, respectively, are -

Answer:
1.0 × 10⁶6 s^-1 and 38.3 kJ mol^-1



5. Identifying bonding patterns and single and double bonds


The nitrogen oxide(s) that contain(s) N-N bond(s) is (are) -


(A) N2O (B) N2O3
(C) N2O4 (D) N2O5

Answer: A,B, and C

6. Sugars : Identifying reducing sugar and nonreducing sugar and glucosidic linkages in the given compounds

7. Identifying the amine in a given reaction


In the reaction
2X + B2H6 → [BH2(X)2]⁺ [BH4]^-

amine (X) is (are)

8. Identifying state functions


Among the following, the state function(s) is (are)-
(A) Internal energy (B) Irreversible expansion work
(C) Reversible expansion work (D) Molar enthalpy

Answer A and D

9 Identifying the scope for spontaneous reaction

10. Reactions of metals with acids


Column I
(A ) Cu + dil HNO3
(B) Cu + conc HNO3
(C) Zn + dil HNO3
(D) Zn + conc HNO3

Matching is to be done with output of the reaction (various compounds)

11. Identifying compounds that are produced from given reactions


(p) Nucleopilic substitution
(q) Elimination
(r) Nucleophilic addition
(s) Esterification with acetic anhydride
(t) Dehydrogenation

Compounds are presented as line diagram format

12. coordination number


The coordination number of Al in the crystalline state of AlCl3 is –

13. Oxidation number
The oxidation number of Mn in the product of alkaline oxidative fusion of MnO2 is –

14. Emission of alpha and Beta particles in a nuclear reaction


The total number of α and β particles emitted in the nuclear reaction U[238,92]
→ Pb[214,82] is –

15. pH of a solution


The dissociation constant of a substituted benzoic acid at 25ºC is 1.0 × 10^-4. The pH of a 0.01M solution of its sodium salt is –

16. organometallic compounds structure


The number of water molecule(s) directly bonded to the metal centre in CuSO4. 5H2O is –

17. Molecular weight and kinetic energy


At 400 K, the root mean square (rms) speed of a gas X (molecular weight = 40) is equal to the most probable speed of gas Y at 60 K. The molecular weight of the gas Y is -

18. Number of Isomers


The total number of cyclic structural as well as stereo isomers possible for a compound with the molecular formula C5H10 is-

19. Enthalpy of Combustion of Gas


In a constant volume calorimeter, 3.5 g of a gas with molecular weight 28 was burnt in excess oxygen at 298.0 K. The temperature of the calorimeter was found to increase from 298.0 K to 298.45 K due to the combustion process. Given that the heat capacity of the calorimeter is 2.5 kJ K^-1, the numerical value for the enthalpy of combustion of the gas in kJ mol^-1 is-

Answer 9