1 Some Basic Principles of Organic Chemistry
Dipole moment is shown by
1) cis-1, 2-dichloroethene 2) trans-1, 2-dichloroethene 3) trans-1 2-dichloro-2 pentene 4) Both (1) and (3)
SOLUTIONS
C is – 1, 2 – dichloro and trans 1, 2- dichloro – 2 – pentene have dipole moment where as in trans – 1, 2 – dichloro ethene bond moments cancel out hence it has μ = OD. The dipole moment is the vector sum of all the bond.
2 Chemical Equilibrium
At equilibrium, the concentrations of N2=3.0 × 10–3 M, O2= 4.2 × 10–3M and NO= 2.8 × 10–3 M in a sealed vessel at 800K. What will be Kc for the reaction N2(g) + O2(g) <=> 2NO(g)
1) 2.4 2) 62.2 3) 6.22 4) 0.622
SOLUTION For the reaction equilibrium constant, Kc can be written as,
3 Alcohols Phenols and Ethers
The best method to prepare cyclohexene from cyclohexanol is by using
1) conc. HCl + ZnCl2 2) conc. H3PO4 3) HBr 4) conc. HCl
Alkene (cyclohexene) will be prepared by dehydration of an alcohol (cyclohexanol) using an acid catalyst such as phosphroic acid (H3PO4)
4 D and F Block Elements
The highest magnetic moment is shown by the transition metal with the configuration:
1) 3d2 2) 3d6 3) 3d7 4) 3d9
The transition metal with most unpaired electrons shows the highest magnetic moment.
3d6 -> 4 unpaired electrons
3d2 -> 2 unpaired electrons
3d7 -> 3 unpaired electrons
3d9 -> 1 unpaired electrons
5 Aldehydes Ketones and Carboxylic Acids
. Which of the following alcohols cannot be obtained by a hydride reduction of an aldehyde or a ketone
SOLUTION
6 D and F Block Elements
In which compounds does vanadium have an oxidation number of +4?
1) NH4VO2 2) K4[V(CN)6] 3) VOSO4 4) CrO2Cl2
Oxidation state of V in NH4VO2is +3. Oxidation state of V in K4[V(CN)6] is +2. Oxidation state of Cr in CrO2Cl2is +6.
And VOSO4=VO2++SO42−; Let the oxidation number of V be X. So, X x(-2) = + 2 ∴X = +4
7 D and F Block Elements
A transition element X has a configuration $$[Ar]3d^4$$, in its +3 oxidation state. Its atomic number is:
1) 25 2) 26 3) 22 4) 19
In +3 oxidation state $$[Ar]3d^4$$ So in metallic state $$[Ar]3d^5 4s^2$$ and metal is Mn (25).
8 Aldehydes Ketones and Carboxylic Acids
Clemmensen reduction of a ketone is carried out in the presence of which of the following reagent?
1) $$Zn-Hg$$ with $$HCl$$ 2) $$LiAl{H}_{4}$$ 3) $${H}_{2}$$ and $$Pt$$ as catalyst 4) Glycol with $$KOH$$
Clemmensen reduction of a ketone is carried out in the presence of $$Zn−Hg$$ with $$HCl$$. This reduction converts carbonyl group to methylene group. It is suitable for compounds that are sensitive to alkali. $$\displaystyle R-CO-CH_3 \xrightarrow [conc \: HCl]{Zn/Hg} R-CH_2-CH_3$$
9 Chemistry in Everyday Life
AThe artificial sweetener, which is a derivative of sucrose, is:
1) stevia
2) saccharin
3) aspartame
4) sucralose
sucralose is derived from sucrose.
10 Atomic Structure
It has been found that nuclides with 2, 8, 20, 50, 82, and 126 protons or neutrons are exceptionally stable. These numbers are referred to as the magic numbers and their existence has led us to: 1) the idea of periodicity in nuclear properties similar to the periodicity of chemical elements in periodic table. 2) the so-called "liquid drop model of the nucleus" 3) the so-called "shell model of the nucleus" 4) have a convenient explanation of "nuclear fission"
The idea of periodicity in nuclear properties similar to the periodicity of chemical elements in periodic table the so-called "shell model of the nucleus".
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