KVPY(CHEMISTRY) Interview questions

KVPY(CHEMISTRY)
1. Arrange the following compounds in increasing order of dipole moment, toluene (I), o-dichlorobenzene (II),
m-dichlorobenzene (III) and p-dichlorobenzene (IV ).
Ans. IV < I < III < II
2. Arrange CN, CN+ and CN– in increasing order of relative stabilities.
Ans. CN– < CN < CN+
3. In which solvent NaCl has maximum solubility ?
Ans. H2O
4. Indicate wether glycine (NH2 – CH2 – COOH) is an acid or a base or both.
Ans. Both (Since in this -NH2 is basic and -COOH is acidic)
5. A reaction between AlCl3 and NH3 is called -
Sol. Neutralisation
6. Which metal is not found in meteorites ?
Sol. Ag, Au
7. What is use of Hall-Heroult cell ?
Ans. Purification of aluminium.
8. What is the difference between corundum and carborundum ?
Ans. Corundum is Al2O3 and carborundum is SiC.
9. In which climate tin cannot be used as structural metal ?
Ans. In cold climate because in cold climate tin becomes brittle.
10. Oxide of which metal is used in sun screen ?
Ans. ZnO
11. What is the chemical formula of fool’s gold ?
Sol. FeS2
12. When an impurity in metal has greater affinity for oxygen and is more easily oxidised than the metal itself,
then which process is used to refine the metal ?
Sol. Cupellation
13. Which compounds act as propellant for rockets ?
Ans. Liquid hydrogen + Liquid oxygen
14. How many H-bonds are formed by a water molecule ?
Ans. 4 O
H
H
15. What is the volume of O2 liberated at NTP by complete decomposition of 100 ml of 2M solution of H2O2 ?
Ans. 2.24 L
Volume strength = 11.2 × M
= 11. 2 × 2 = 22.4 L
 1000 ml = 22.4 L
 100 ml =
1
100
1000
22.4 
= 2.24 L
16. Zinc gives H2 gas with conc. H2SO4 and conc. HCl but not with conc. HNO3. Why ?
Ans. NO3
– ion is reduced to NO2 in prefercence to H3O+ ( hydronium) ion.
17. A compound of mercury which used in cosmetics, in Ayurvedic and Yunani medicnes and known as Vermil
lion.s
Ans. HgS
18. ‘Bordeaux mixture’ is used as fungicide. Write its composition.
Ans. CuSO4 + Ca(OH)2
19. Name the metals present in insulin, haemoglobin and vitamin B12 respectively.
Ans. Zn, Fe, Co
20. A substance X is a compound of an element of group IA. The substance X gives violet colour in flame test,
X is :
Ans. KCl
21. Why is Na2S2O3. 5H2O used in photography ?
Ans. To remove decomposed AgBr as a soluble complex.
22. What are the products of electrolysis of concentrated common salt solution ?
Ans. NaOH, H2, Cl2
23. What happenss when a standard solution of NaOH is left in air for a few hours ?
Ans. Strength will decrease of NaOH solution.
24. Which impurities in crude common salt are responsible for its hygroscopic nature ?
Ans. CaCl2 and MgCl2
25. CO2 gas along with solid (Y) is obtained when sodium salt (X) is heated. (X) is again obtained when CO2 gas
is passed into aqueous solution of (Y). (X) and (Y) are :
Ans. NaHCO3, Na2CO3
2NaHCO3 Heat Na2CO3 + H2O + CO2
(X) (Y)
Na2CO3 + H2O + CO2  2NaHCO3
(X) (Y)
26. On heating a mixture containing 1 mole each of Li2CO3 and K2CO3 ------- mole of ------- gas(es) is/are formed.
Ans. One mole of CO2
Sol. Li2CO3 decomposes while K2CO3 is stable and does not decompose.
Li2CO3  Li2O + CO2
1 mole 1 mole 1 mole
27. There is loss in mass when mixture of Li2CO3 and Na2CO3.10H2O is heated strongly. The loss is due to :
Ans. Both Li2CO3 and Na2CO3.10H2O
Sol. Li2CO3 Heat Li2O + CO2
Na2CO3 . 10H2O HeatNa2CO3 + 10H2O
28. Metal (M) + N2 Nitride H2ONH3 . The metal (M) is -
Ans. Li, Mg
29. Na2O2 has light yellow colour. This is due to :
Ans. Presence of trace of NaO2 .
30. Water is added to calcium carbide and the evolved gas is passed through dilute H2SO4 containing HgSO4.
Which organic compound are formed ?
Ans. CH3CHO
Sol. CaC2 + 2H2O  C2H2 + Ca(OH)2
CH  CH + HOH
2 4
4
H SO
HgSO CH = CH 2
OH
CH – CHO 3
31. The nitrate (A) can be confirmed by flame test. The colour imparted by the salt to the flame is -
Ans. Green
32. Why Gypsum is added to portland cement ?
Ans. To slow down the process of setting.
33. A colourless gas which burns with blue flame and reduces CuO to Cu is -
Ans. CO
34. Carbon has valency four in CH4. What is its valency in acetylene ?
Ans. 4
35. Why H2SO4 is not used for the preparation of CO2 from marble chips ?
Ans. Calcium sulphate is sparingly soluble and get deposited on marble chips and stops the reaction.
36. Which type of glass has the smallest coefficient of thermal expansion ?
Ans. Pyrex glass
37. How is colour is imparted to glass ?
Ans. By adding metal oxides
38. In the ring test for nitrates, the ring formed is due to formation of -
Ans. FeSO4. NO
39. Oxalate + MnO2 + dil. H2SO4  Gas. The gas evolved is :
Ans. CO2
40. A gas is evolved which burns with blue flame when the mixture is heated with conc. H2SO4. The mixture
contains :
Ans. Oxalate/Carbonate
41. Which metal sulphide is yellow in colour ?
Ans. ZnS / PbS
42. A mixture when rubbed with organic acid, smells like vinegar. It contains :
Ans. CH3COO– acetate
43. All ammonium salts liberate ammonia when -
Ans. Heated with caustic soda
Sol. 2NH4Cl + 2NaOH  2NH3 + 2NaCl + 2H2O
44. Which of the following gives green colour to the flame ?
(i) BaCl2 (ii) CaCl2
Ans. BaCl2
45. Which of the following compound does not dissolve in hot dil. HNO3 ?
(i) HgS (ii) PbS
Ans. HgS
46. What is nessler’s reagent ?
Ans. K2HgI4
47. An object is located at a height of 5 km from the surface of the earth. The object is located in which part of
atmosphere ?
Ans. Troposphere
48. Which gases are absorbers of IR-radiation ?
Ans. Carbondioxide and chlorofluorocarbons.
49. Write formula for tear gas.
Ans. CCl3NO2
50. Which metal is used for drying organic solvents ?
Ans. Na