1 Haloalkanes and Haloarenes
Which major product is formed in the free-radical bromination of methane by limited supply of bromine?
1) Bromomethane
2) Dibromomethane 3) Tribromomethane 4) Tetra bromomethane
CH4 + Br2 --freeradical−→CH3−Br
Free Radical Mechanism
CH3−H→CH?3+H?
Br−Br→Br?+Br?
⇒CH?3+Br?→CH3−Br (bromomehane)
H?+Br?→ H−Br
⇒ Bromomethane is mojor product.
2 Surface Chemistry
Methylene blue, from its aqueous solution, is adsorbed on activated charcoal at 25oC. For this purpose the correct statement is:
1) The adsorption requires activation at 25oC 2) The adsorption is accompanied by a decrease in enthalpy 3) The adsorption increases with increase of temperature 4) The adsorption is irreversible
Methylene blue, from its aqueous solution, is adsorbed on activated charcoal at 25 degree Centigrade. For this purpose the correct statement is The adsorption requires activation at 25 degree centigrade.
3 Stoichiometry
In Haber process 30 litres of dihydrogen and 30 litres of dinitrogen were taken for reaction which yielded only 50% of the expected product. What will be the composition of gaseous mixture under the aforesaid conditionin the end? 1) 20 litres ammonia, 20 litres nitrogen, 20 litres hydrogen 2) 10 litres ammonia, 25 litres nitrogen, 15 litres hydrogen 3) 20 litres ammonia, 10 litres nitrogen, 30 litres hydrogen 4) 20 litres ammonia, 25 litres nitrogen, 15 litres hydrogen
Reaction N2 + 3H2 → 2NH3 Hydrogen is 30 L thus requires 10 Nitrogen Hydrogen is limiting reagent Now only 50% of Hydrogen is used = 15 and Balance hydrogen =15L Therefore 5 L of Nitrogen used and 30-5 = 25 Balanced NH3 Produced = 10 L
4
Given that Zn + ½ O2 --> ZnO + 35.28 kj HgO --> Hg + ½ O2 - 9.11 kj so the heat of reaction Zn + HgO --> ZnO + Hg is 1. 26.17 kj 2. 44.39 kj 3. -44.39 kj 4. 2.617 kj.
5 Coordination Compounds
Among the ligands NH3, en, CN– and CO the correct order of their increasing field strength, is:
SOLUTION
6 S – Block Elements
The starting material used in Solvay's process is
1) Brine solution
2) Sodium sulphate
3) Carnallite
4) All of them together
7 Chemical Thermodynamics
?E° of combustion of iso-butylene is -X kJ mol -1 . The value of ?H° is
1) = ?E° 2) > ?E° 3) = 0 4) < ?E°
SOLUTIONS
8 Purification and Characterisation of Organic Compounds
Elution is the process for:
1) crystallization of compound
2) separation of compound
3) extraction of compound
4) distillation of compound
Elution is the method of extracting one material from another by washing with a solvent. It is used in the washing of loaded ion-exchange resins to remove captured ions in analytical and organic chemistry.
9 Atomic Structure
Which of the following has maximum number of zero values appear in the curve plotted between ψ2 (probability of finding electron) versus radius? 1) 3p 2) 4d 3) 5p 4) 4f
Maxm no. of zero values is given by total no. of nodes which is given by ⇒n−1.
n−1 principle quantum number
10 Classification of Elements and Periodicity
The ions O2−, F−, Na+, Mg2+ and Al3+ are isoelecronic. Their ionic radii show: 1) a significant increase from O2− to Al3+ 2) a significant decrease from O2− to Al3+ 3) an increase from O2− to F− and then decrease from Na+ to Al3+ 4) an decrease from O2− to F− and then increase from Na+ to Al3+
As all the given species are iso electronic, the ionic radii decreases with increasing atomic number as effective nuclear charge increases. Hence from O2− to Al3+, the size decreases significantly
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