1 Thermodynamics
Given C + 2S → CS2 , ΔHfo=+ 117.0 kJ/mol C+ O2 → CO2 , ΔHfo=- 393.0 kJ/mol S+ O2 → SO2 , ΔHfo=- 287.0 kJ/mol The heat of combustion of CS2 + 3O2 → CO2 + 2SO2 is 1) - 807 kJ/mol 2) -1104 kJ/mol 3) +1104 kJ/mol 4) +807 kJ/mol
Add equations C+ O2 → CO2 , ΔHfo=- 393.0 kJ/mol and 2( S+ O2 → SO2 , ΔHfo=- 287.0 kJ/mol) Resultant is C+ 2S + 3O2 → CO2 + 2SO2 ( -393 - 2×287 = -987 kJ ) By subtracting C + 2S → CS2 , ΔHfo = + 117.0 kJ/mol from above equation we get CS2 + 3O2 → CO2 + 2SO2 ( -987 - 117=-1104 kJ /mol)
2 Chemistry in Everyday Life
Which of the following fertilizers does not replenish nitrogen in the soil? :
1) CAN 2) Urea 3) Super phosphate lime. 4) Ammonium phosphate
Superphosphate lime is produced by treating rock phosphate with sulfuric acid. It is the principal carrier of phosphate, the form of phosphorous usable by plants.
3 Hydrocarbons
Nitrobenzene on reaction with conc. HNO3/H2SO4 at 80-100°C forms which one of the following products?
1) 1,2-dinitrobenzene 2) 1,3-dinitrobenzene 3) 1,4-dinitrobenzene 4) 1,2,4-trinitrobenzene
SOLUTION
4 Hydrogen
Hydrogen gas is liberated by the action of aluminium with a concentrated solution of
1) NaHCO3 2) Na2CO3 3) NaOH 4) none of these
2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H2
This reaction is extremely quick and produces a lot of energy.
This reaction occurs because AlAl is always covered by a layer of un-reactive Al2O3 layer has to be taken down first.
5 Alcohols Phenols and Ethers
Among the following, the compounds nitrobenzene, benzene, aniline and phenol the strongest basic behaviour in acid medium exhibited by 1. phenol 2. aniline 3. nitrobenzyne 4. benzene
Because the N atom in amiline has a lone pair to donate and also due to +I effect of −NH2 group.
6 Surface Chemistry
Calculate the surface area in (sq m) of a catalyst that adsorbs 103cm3 of nitrogen reduced to STP per gram in order to form the monolayer. The effective area (in m2) occupied by N2? molecule on the surface is: ( surface area of N2?=1.62×10−15cm2)
1) 4115 m2 2) 2355 m2 3) 4355 m2 4) 435.5 m2
According to the given data,
Number of N2? molecules = Volume(ml) × NA / Volume at STP(in ml)
= (103×6.023×1023) / 22400 = 2.69×1022
Total area covered by N2? = 2.69×1022 × 1.62×10−15 = 435×105 cm2 = 4355 m2.
7 Basic Principles of Organic Chemistry
The number of enantiomers of the compound CH3CHBrCHBrCOOH is
1) 0
2) 1
3) 3
4) 4
There are two chiral carbons.
Hence the number of isomers are 22=4
8 Aldehydes Ketones and Carboxylic Acids
The correct sequence of decreasing order of reactivity of hydrolysis of acid chlorides is :
1) PhCOC l> p−O2NC6H4COCl > p−CH3OC6H4COCl 2) PhCOCl > p−CH3OC6H4COCl > p−O2NC6H4COCl 3) p−O2NC6H4COCl > PhCOCl > p−CH3OC6H4COCl 4) p−O2NC6H4COCl > p−CH3OC6H4COCl > PhCOCl
The hydrolysis of acid chloride involves a nucleophilic attack on the fairly positive carbon atom by one of the lone pairs on the oxygen of a water molecule.
9 Mole Concept
If a mixture containing 3 moles of hydrogen and 1 mole of nitrogen is converted completely into ammonia, the ratio of initial and final volumes at the same temperature and pressure would be :
1) 1:2 2) 2:1 3) 1:3 4) 3:1
10 Titrations
When MnO4−? and I− react in a strongly basic solution, the products will most likely be :
1) Mn and I2?
2) MnO42−?, IO3?−
3) MnO2?,O2?,IO−
4) Mn2+, I2?
The reaction between MnO4−? and I−? is as follows: 12MnO4−?+I− + 6OH−→6(MnO4?)2−+(IO3?)−+3H2?O Therefore, the products are likely to be MnO42−? and IO3−?.
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