chemistry today - may 2013 (gnv64)
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www.mtg.iri | May 2013
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edit Q rialResearch on Superspecialities beckons youhe 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 followed by research of the highest order, at par with 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 w e 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? Anil Ahlawat EditorSubscribe online a t W W W . m t g . i n
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ContentsAIIMS Special: Assertion and Reason 6
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2 CHEMISTRY TODAY | MAY '13
Directions : Mark the correct choice as:
AIIMSSpecialPHYSICAL CHEMISTRY 1.
(a) (b) (c) (d)
If both assertion and reason are true and reason is the correct explanation of assertion. If both assertion and reason are true but reason is not the correct explanation of assertion. If assertion is true but reason is false. If both assertion and reason are false. negative when anhydrous salts capable of forming hydrates are dissolved in water. : 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.
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. Assertion : The decomposition of NH 3 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. Assertion : In the reaction,
Assertion : SeCl 4 does not have a tetrahedral Reason structure. : Se in SeCl 4 has two lone pairs of electron. in
Assertion : Equivalent weight of K M n 0 4
so2fe) + Cl2fe), the reaction shifts to backward direction on increasing pressure. : The increase in pressure at equilibrium shifts the reaction towards lesser number of moles.
acidic medium is M/5 (M = mol. wt.) while in basic medium, it is equal to M/3. : In acidic medium, 1 mol of M n 0 4 gains 5 electrons while in basic medium it gains 3 electrons.
Assertion : Galvanic cells containing hydrogen, methane, methanol etc. as fuels are called fuel cells. : They are designed to convert the energy of combustion of fuels directly into electrical energy. BC13. : The planar BF3 molecule is stabilized to a greater extent than BC13 by B - X n -bonding.
4. , Assertion : Zinc blende and wurtzite both have fee arrangement of sulphide ions. Reason : There are four formula units of ZnS in both. 5. Assertion : Enthalpy changes are positive w h e nNa2S04 -10H20, CUS04 -5H20 and
Assertion : BF3 is a weaker Lewis acid than Reason
salt like NaCl, KC1 etc. (which do not form hydrates) are dissolved in water. But enthalpy changes are3 CHEMISTRY TODAY | MAY '13
10. A s s e r t i o n : l n
orbit is possible for the electron in K-shell. : Electron present in JC-shell c o r r e s p o n d s to principal q u a n t u m n u m b e r n = 1. ORGANIC CHEMISTRY
O II CH3-CH2- C-NH2Reason : (CH 3 ) 2 CH migrates faster t h a n C H 3 C H 2 at electron-deficient n i t r o g e n atom.
11. A s s e r t i o n : Cyclohexanone Reason
tautomerism. : In cyclohexanone, one form contains the keto g r o u p (C = 0 ) while other contains enolic g r o u p (-C= C-OH)
18. A s s e r t i o n : M e 3 N reacts w i t h BF 3 w h e r e a s P h 3 N d o e s not. Reason : The electron pair o n nitrogen a t o m in P h 3 N is delocalised in the b e n z e n e ring a n d is n o t available to b o r o n in BF 3 . 19. A s s e r t i o n : Fructose does n o t contain an a l d e h y d e g r o u p b u t still reduces Tollen's reagent. Reason : In presence of a base, fructose u n d e r g o e s r e a r r a n g e m e n t to f o r m a molecule containing an a l d e h y d e group. O 20. A s s e r t i o n : H C O H O II HO-C-OH. Reason : - H is electron releasing while - O H is electron w i t h d r a w i n g g r o u p . INORGANIC CHEMISTRY 21. A s s e r t i o n : N i t r o g e n is unreactive at r o o m t e m p e r a t u r e b u t b e c o m e s reactive at elevated t e m p e r a t u r e s (on heating) or in the presence of catalyst. Reason : In nitrogen molecules, there is extensive derealization of electrons. 22. A s s e r t i o n : F - a t o m h a s less negative electron affinity t h a n CI-atom. Reason : A d d i t i o n a l electrons are repelled m o r e effectively b y 3p- electrons in C I - a t o m t h a n b y 2p- electrons in F-atom. 23. A s s e r t i o n : A1 is obtained b y h i g h t e m p e r a t u r e r e d u c t i o n of a l u m i n a w i t h carbon. Reason : A l u m i n a reacts w i t h carbon to f o r m a l u m i n i u m carbide w h i c h d e c o m p o s e s at h i g h t e m p e r a t u r e to is less acidic than
12. A s s e r t i o n : Oxiranes are cleaved u n d e r acidic Reason a n d basic conditions. : The oxirane ring is strained a n d the tetrahedral b o n d angle (109.5) is distorted to 61.5
13. Assertion : Greater the stability of carbanion, greater is its ease of f o r m a t i o n a n d hence, m o r e reactive is the aryl halide. Reason Chlorobenzene is less reactive t h a n p-chloroanisole t o w a r d s nucleophilic substitution reactions. 14. Assertion : Ethanal o n t r e a t m e n t w i t h selenium dioxide can be converted into glyoxal. Reason : S e 0 2 oxidizes the m e t h y l e n e g r o u p adjacent to C = 0 g r o u p in a l d e h y d e s or ketones to carbonyl g r o u p . 15. A s s e r t i o n : m-Chlorobenzoic acid is a stronger Reason acid t h a n p-chlorobenzoic acid. : In wi-chlorobenzoic acid both - /-effect a n d + R- effect of CI operate b u t in p-ch