1 Atomic Structure
Oxygen contains 90% O16 and 10% O18 Its atomic mass is:
1) 16.2 2) 17.4 3) 17. 4) 16.5.
2 Redox Reactions
Four Cl2 molecules undergo a loss and gain of 6 mole of electrons to form two oxidation states of Cl in auto redox change. What are the +ve and −ve oxidation states of Cl in the change:
1) Cl5+,Clo 2) Cl7+,Cl- 3) Cl3+,Clo 4) Cl3+,Cl-
SOLUTION
The overall reaction is:
4Cl2 → 2Cl+3 + 6Cl−
Here total number of atom is balanced and total charge is balance.
Change of oxidation state is +3 and -1.
3 Hydrogen
H2?O2? + H2O → H3?O+ + HO2−?
The reaction indicates:
1) H2?O2? is a bleaching agent 2) H2?O is more acidic than H2??O2? 3) H2?O2?? is more acidic than H2?O. 4) both H2?O2?? and H2??O are acidic
H2O is acting as a base in the above reaction as it accepts the proton. Thus, in presence of H2?O2?, water acts as a base and hence, hydrogen peroxide is more acidic.
4 States of Matter
A sample of gas occupies 300 dm3 at 27oC and 750 pressure. What contraction in volume takes place, when the gas is cooled to - 33oC at 750 mm pressure?
1) 120 dm3
2) 240 dm3
3) 60 dm3
4) No change in volume
Solution
At constant pressure, V1 /T1 = V2 /T2 ;
V1 = 300 dm3 ; V2 = ?, T1 = 300K, T2 = 273 – 33 = 240 K;
V2 = (V1 /T1 ).T2 = (300/300) ´ 240 = 240 dm3
decrease in volume = 300 – 240 = 60 dm3
5 Solutions
An aqueous solution of non-electrolyte 'A' with molecular mass 60 contains 6 g in 500 ml and has a density equal to 1.05. The molality of solution is
1) 0.30
2) 0.25
3) 0.19
4) 1.25
Mass of solution =500×1.05=525g Mass of solvent =525−6=519g
Molality = $$\displaystyle=\frac{{{6}\times{1000}}}{{{60}\times{519}}}={0.192}{M}$$
6 Environmental Chemistry
The function of automobile catalytic converter is to control emissions of:
1) carbon dioxide and hydrogen
2) carbon monoxide and hydrogen
3) carbon monoxide and carbon dioxide
4) carbon monoxide and nitrogen dioxide
CA catalytic converter is an emissions control device that converts toxic gases and pollutants in exhaust gas to less toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction).
Catalytic converters are used with internal combustion engines fueled by either petrol (gasoline) or diesel—including lean-burn engines as well as kerosene heaters and stoves.
These "two-way" converters combined oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide and water.
7 General Principles & Process of Isolation of Metals
Greyish white metal which is a good conductor of electricity and heat and has a boiling point of 920?C is : 1) aluminium 2) tin 3) iron 4) zinc
Greyish white metal which is a good conductor of electricity and heat and has a boiling point of $$920^\circ C$$ is zinc.
8 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
9 P – Block Elements
Ammonia gas dissolves in water to form NH4OH. In this reaction water acts as :
1) A conjugate base 2) A non-polar solvent 3) An acid 4) A base.
NH3?+H2?O → NH4+? +OH−
Water acts as a proton donor in this reaction. Since, a proton donor is an acid, water acts a Bronsted-Lowry acid.
10 Chemical Bonding and Molecular Structure
The correct sequence of decrease in the bond angle of the following hydrides is 1) NH3 > PH3 > AsH3 > SbH3 2) NH3 > AsH3 > PH3 > SbH3 3) SbH3 > AsH3 >PH3 > NH3 4) PH3 > NH3 > AsH3 > SbH3
More the electronegative central atom more the bond angle
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