chemistry today - may 2013 (gnv64)
Post on 19-Jan-2016
Embed Size (px)
www.mtg.iri | May 2013
l e a r n i n g M e d i a
NCERTXtract Trust of more than 1 Crore Readers
JEE AIIMS JEE NEET SPECIAL PMTs ADVANCED M A I N
CHEMISTRY Vol. XXII No. 5 May 2013 Corporate Office: Plot 99, Sector 44 Institutional area,
Gurgaon -122 003 (HR). Tel: 0124-4951200 e-mail: email@example.com website : www.mtg.in
Regd. Office 406, Taj Apartment, Near Safdarjung Hospital, Ring Road, New Delhi -110029.
Managing Editor Mahabir Singh Editor : Anil Ahlawat (BE, MBA)
AIIMS Special: Assertion and Reason 6
NEET Special (Scrapbook) 13
NCERT Xtract 21
Practice Paper: AIIMS 29
Practice Paper: JEE Advanced 38
Quick Revision of 46 Inorganic Chemistry (Part-ll)
Solved Paper: JEE Main 60
Practice Paper: Target PMTs 64
Concept Booster 72
Brainstorming Problems 80 (Physical Chemistry)
Owned, Printed and Published by Mahabir Singh from 406, Taj Apartment, New Delhi - 29 and printed by Personal Graphics and Advertisers (P) Ltd., Okhla Industrial Area, Phase-11, New Delhi. Readers are adviced to make appropriate thorough enquiries before acting upon any advertisements published in this magazine. Focus/Infocus features are marketing incentives MTG does not vouch or subscribe to the claims and representations made by advertisers. All disputes are subject to Delhi jurisdiction only. Editor: Anil Ahlawat Copyright MTG Learning Media (P) Ltd. All rights reserved. Reproduction in any form is prohibited.
edit Q rial Research on Superspecialities beckons you
The system of Ayurveda is as old as the ancient history of India. Luckily for us, in spite of repeated invasions, we had retained the purity of our ancient knowledge. We are also absorbing modern systems of knowledge fol lowed by research of the highest order, at par wi th any nation. However in the these days, we have also to learn to make money like the developed countries. India has a large population because the area of the continent is as much as Europe and Britain, excluding the older Russia. A large population with many states and universities and research institutions is our asset. We also need a large quantity of allopathic medicines for our people. Many of them are patented. These medicines are also having forbidding costs. However, many of their patents also lapse. Are we ready to substitute the generic medicines to replace imported ones? We have to completely map the medicines, study their structure and reproduce the generic one of every available medicine including those with patents so that the day the patents lapse for them, one can start making them for our use. We know that there are very powerful and useful medicines produced by not only Ayurvedic laboratories but also Unani and Homeopathy. We know their composition. But we do not know which molecule is attacking the parasites in blood, their mode of action and applicability have not been tried before for our systems of medicine. It is a life-time research for many scientists and for generations this will be continued. Every single instrument ranging from X-ray spectroscopy, diffraction and scanning, U.V., I.R. etc. should be used to study them. Then experiments on their action on various molecules of the polluted blood has to be continued. Once one can establish their utility for controlling the disease is proved, one has taken a wicket. The game continues. Don't you like to play super-games?
Ani l Ah lawat Editor
Subscribe online a t W W W . m t g . i n
Individual Subscription Rates Combined Subscription Rates 1 yr. 2 yrs. 3 yrs. 1 yr. 2 yrs. 3 yrs.
Mathematics Today 300 500 675 PCM 800 1200 1700 Chemistry Today 300 500 675 PCB 800 1200 1700 Physics For You 300 500 675 PCMB 900 1500 2100 Biology Today 300 500 675 Send D.D/M.0 in favour of MTG Learning Media (P) Ltd. Payments should be made directly to : MTG Learning Media (P) Ltd, Plot No. 99, Sector 44, Gurgaon - 122003 (Haryana) We have not appointed any subscription agent.
2 CHEMISTRY TODAY | MAY '13
A S S E R T I O N R E A S O N
Directions : Mark the correct choice as:
1. Assertion : The volume of a gas is directly proportional to the number of moles of the gas.
Reason : The ratio of the volumes of the reactants to products are in agreement with their molar ratio.
2. Assertion : The decomposition of NH3 on finely divided platinum surface is first order when the concentration is low, however at higher concentration, the reaction becomes zero order.
Reason : In first order reaction, the rate of reaction is proportional to the first power of the concentration of the reactant.
3. Assertion : In the reaction, so2ci2te) so2fe) + Cl2fe),
4. , Assertion
the reaction shifts to backward direction on increasing pressure.
: The increase in pressure at equilibrium shifts the reaction towards lesser number of moles.
: Zinc blende and wurtzite both have fee arrangement of sulphide ions.
: There are four formula units of ZnS in both.
: Enthalpy changes are positive when N a 2 S 0 4 - 1 0 H 2 0 , C U S 0 4 - 5 H 2 0 a n d
salt like NaCl, KC1 etc. (which do not form hydrates) are dissolved in water. But enthalpy changes are
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false. (d) If both assertion and reason are false.
negative when anhydrous salts capable of forming hydrates are dissolved in water.
Reason : The difference in the behaviour is due to large difference in the molecular weights of hydrated and anhydrous salts. The substance with larger molecular weight usually shows positive enthalpy changes on dissolution.
6. Assertion : SeCl4 does not have a tetrahedral structure.
Reason : Se in SeCl4 has two lone pairs of electron.
7. Assertion : Equivalent weight of KMn0 4 in acidic medium is M/5 (M = mol. wt.) while in basic medium, it is equal to M/3.
Reason : In acidic medium, 1 mol of M n 0 4 gains 5 electrons while in basic medium it gains 3 electrons.
8. Assertion : Galvanic cells containing hydrogen, methane, methanol etc. as fuels are called fuel cells.
Reason : They are designed to convert the energy of combustion of fuels directly into electrical energy.
9. Assertion : BF3 is a weaker Lewis acid than BC13.
Reason : The planar BF3 molecule is stabilized to a greater extent than BC13 by B - X n -bonding.
3 CHEMISTRY TODAY | MAY '13
10. Asser t ion : l n Sommerfeld model , circular orbit is possible for the electron in K-shell.
Reason : Electron present in JC-shell corresponds to principal q u a n t u m n u m b e r n = 1.
11. Asser t ion : Cyclohexanone exhibits keto-enol tautomerism.
Reason : In cyclohexanone, one form contains the keto g roup (C = 0 ) while other contains enolic g roup ( - C = C - O H )
12. Asser t ion : Oxiranes are cleaved u n d e r acidic and basic conditions.
Reason : The oxirane ring is strained and the tetrahedral b o n d angle (109.5) is distorted to 61.5
Greater the stability of carbanion, greater is its ease of format ion and hence, more reactive is the aryl halide. Chlorobenzene is less reactive than p-chloroanisole towards nucleophilic subst i tut ion reactions.
14. Assert ion : Ethanal on t reatment wi th selenium dioxide can be converted directly into glyoxal.
Reason : S e 0 2 oxidizes the methylene g r o u p adjacent to C = 0 g roup in a ldehydes or ketones to carbonyl group.
15. Asser t ion : m-Chlorobenzoic acid is a s tronger acid than p-chlorobenzoic acid.
Reason : In wi-chlorobenzoic acid bo th - /-effect and + R- effect of CI operate but in p-chlorobenzoic acid only +R- effect of CI operates.
16. Assert ion : -Annulene is not aromatic though it contains Huckel n u m b e r of Tt-electrons.
Reason : Steric interaction be tween internal hydrogens makes it non-planar .
17. Asser t ion : ( C H 3 ) 2 C H C N H 2 undergoes faster H o f m a n n - b r o m a m i d e
reaction in compar ison to O II
C H 3 - C H 2 - C - N H 2 -
(CH3)2CH migrates faster than C H 3 C H 2 at electron-deficient n i t rogen atom.
Me 3 N reacts wi th BF3 whereas Ph 3 N does not. The electron pair on ni t rogen a tom in Ph 3 N is delocalised in the benzene ring and is no t available to boron in BF3.
Fructose does not contain an a ldehyde g r o u p bu t still reduces Tollen's reagent. In presence of a base, fructose undergoes rear rangement to form a molecule containing an a ldehyde group.
O 20. Asser t ion : H C O H is less acidic than
H O - C - O H .
Reason : - H is electron releasing while - O H is electron wi thd rawing group.
INORGANIC CHEMISTRY 21. Asser t ion : Ni t rogen is unreact ive at room
tempera tu re bu t becomes reactive at elevated tempera tures (on heating) or in the presence of catalyst.
Reason : In ni t rogen molecules, there is extensive d e r e a l i z a t i o n of electrons.
F-a tom has less negative electron affinity than CI-atom. Addi t ional electrons are repelled more effectively by 3p- electrons in CI-a tom than by 2p- electrons in F-atom.
A1 is obtained by high tempera ture reduct ion of a lumina wi th carbon. Alumina reacts wi th carbon to form a lumin ium carbide which decomposes at h igh tempera ture to
13. Assert ion :