interview questions

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Question 1 .What do you mean by a mole ?

Ans.    ‘A mole is defined as the number equal to the number of carbon atoms in exactly 12 grams of pure carbon-12″

            No. of C-atoms in 12 grams of carbon-12=6.023×1023


1 mole = 6.023×1023  i.e. Avogadro’s number.

Question 2.What is normality?

Ans.    Number of gram equivalents present in one litre of solution, is called normality of solution.

Question3. What do you mean by ‘5N’ solution?

Ans.    When 5gm. equivalents of solute are present in one litre of solution, then normality of soution is ‘5N’

Question4.What do you mean by N/10 or 1/10 N solution?

Ans     When 1/10 gram equivalents of solute are present in one litre of solution, then normality of solution is 1/10.

Question5. What is molarity?

Ans.    Number of moles of solute present in one litre of solution is called molarity of solution.

Question6.What do you mean by 10M solution?

Ans.    When 10 moles of solute are dissolved in one litre of solution, then solution is 10M.

Question7. What do you mean by M/1000 solution?

Ans.    When 1/1000 moles of solute are present in one litre of solution, then it is M/1000.

Question8. What is molality?

Ans. Number of moles of solutes present in 1 kg of solvent, is called Molality of solution.

Question9. What do you mean by one molal (1m) solution?

Ans.    When one mole of solute is dissolved in 1kg of solvent, then solution is one molal.

Question10. What do you mean by m/100 solution?

Ans.    1/100 mole of solute is dissolved in one Kilogram of solvent, then solution is 1/100 m or m/100.

Question11. What is the unit of normality, molarity & Molality?

Ans.    Unit of normality= gram equivalents/litre

Unit of Molarity = Moles/litre

Unit of Molarity = Moles/Kg

  1. Electronic Configuration of Cr, Cu, Pd, Ag, Au

Ans.    24Cr      –          1s2,2s2,2p6,3s2,3p6,4s1,3d5

29Cu     –          1s2,2s2,2p6,3s2,3p6,4s1,3d10

46Pd     –          1s2,2s2,2p6,3s2,3p6,4s2,3d10,4p6,5s0,4d10

 47Ag     –          1s2,2s2,2p6,3s2,3p6,4s2,3d10,4p6,5s1,4d10

79Au     –          1s2,2s2,2p6,3s2,3p6,4s2,3d10,4p6,5s2,4d10,5p6,6s1,4f14,5d10

  1. Electronic Configuration of Cu+,Cu++,Ag+,Na+,O– –

29Cu+               –          1s2,2s2,2p6,3s2,3p6,4s0,3d10

29Cu++              –          1s2,2s2,2p6,3s2,3p6,4s0,3d9

47Ag+               –          1s2,2s2,2p6,3s2,3p6,4s0,3d10,4p6,5s0,4d10

11Na+               –          1s2,2s2,2p6

8O– –                 –          1s2,2s2,2p6

Question12.Define Acid & base according to Arrhenius concept?

Ans.    An acid is a substance which gives hydrogen ion (H+) is aqueous solution

Ex                    HCl –>H++Cl




A base is a substance which gives hydroxide ion (OH) in aqueous solution.

Ex.                   KOH (aq.) –> K++OH

NaOH (aq.) –>Na+ +OH

 Question13. Define Acid  & base according to Bronsted Lowry Concept?

Ans.    An acid is a substance (molecule or cation or anion)

that gives proton i-e H+

HCl –> H++Cl

A base is a substance (molecule or cation or anion) that accepts proton i-e H+

H+ +CN –> HCN

Question14.Define Acid & base according to Lewis concept?

Ans.    Lewis acid is lone pair acceptor  Lewis base is lone pair donar.

[H3N:   –>    BF3]

Lone pair         Lone pair

donar               acceptor

(Lewis base) (Lewis Acid)

Question15.What is the equivalent weight of Anhy. oxalic acid & hydrated oxalic acid?

Ans.    Anhy oxalic acid = H2C2O4 or

hydrated or Crystalline oxalic acid = H2C2O4.2H2O or  2H2O

Mol wt of H2C2O4      = 2×1+2×12+4×16=90

oxalic acid is dibasic acid

basicity of oxalic acid= 2

Eq. Wt. of H2C2O4= 90/2 = 45 Ans.

Mol. wt of H2C2O4.2H2O =2×1+2×12+4×16+2×18=126

Eq. Wt. of H2C2O4.2H2O = 126/2 = 63 Ans

Question16. What is the equivalent weight of K2Cr2O7 in Acidic medium?   .

Ans.Molecular weight of K2Cr2O7 = 2×39+2×52+7×16

= 294

n= no. of atoms of that element whose oxidation no. is changing

n= 2

Eq. Wt. =  Ans

Question17. What is Mohr salt. Calculate its equivalent weight?

Ans.    Mohr salt is ferrous Ammonium sulphate Its formula is FeSO4(NH4)2SO4.6H2O.

(Ferrous sulphate of mohr salt)

Mol. Wt. of Mohr Salt = 56+32+16×4 +6×18

= 392

Question18. Calculate equivalent weight of potassium permanganate (KMnO4) in Acidic, Basic and neutral medium?

Ans.    In Acidic Medium

Mol. Wt. of KMnO4 = 39+55+16×4 =158

Change in O No. of Mn = 5


In Neutral Medium-

In Basic Medium

Question19. What is green house effect and global warming?

Ans.    Light from the sun travels through the atmosphere and is absorbed by the Earth. This light is converted to infrared radiation. Much of this infrared radiation is emitted back to the atmosphere. Certain gas molecules absorb part of the radiation, storing the heat energy in the atmosphere & thus warming the air. This process is called green house effect.

                        Carbon dioxide, methane, nitrous oxide, ozone, CFCs (Chlorofluoro carbons), water vapour and carbon tetrachloride are the principal green house gases.

The gradual increase in the overall temperature of earth is called global warming.

Question20. What is Acid Rain?

Ans.    The normal rainwater has a pH of 5.6 This slightly acidic pH is due to formation of H+ ions formed by the action of CO2 (of air) with water

            H2O(l) + CO2(g) –> 2H++CO3– –

when the pH of raindrop is below 5.6, it becomes acid rain. The acidity in rain is created by the presence of oxides of nitrogen & sulphur in the atmosphere. These oxides are produced by fossil fuel combustion, smelting, petroleum refining & sulphur based industries.

These oxides combine with water & produces HNO3, H2SO4 & HCl. These form acidic preparation, which is known as acid rain.

Acid rain causes extensive damage to building & sculptural materials of marble, limestone, slate, mortar etc.

Question21.What is green chemistry?

Ans.     Green chemistry may be called chemistry involved in the design, development and implementation of chemical products and processes  to reduce or eliminate the use and generation of substances hazardous to human health and the environment.

Question22. What is the effect of reforestation on water lable?

Ans.    More trees by reforestation transpire more water vapour, thereby helping in causing more rain falls, which will ultimately raise the under ground water lable.

Question 23.What is aromaticity?

Ans.    Aromaticity is defined as a property of sp2 hybridised planar rings in which the p-orbitals (one on each atom) allow cyclic delocalization of II-electrons. Criteria of aromaticity are

  1. The compound is cyclic and planar
  2. Each atom in the ring has a p-orbital that provides continuous overlap.
  3. The cyclic p-molecular orbitals formed by overlapping of p-orbitals must contain [4n+2] p Where n is an integer =0,1,2,3. This is called Huckel Rule



Image result for benzene ring sign



= 6 π electrons



Image result for naphthalene sign



= 10 π electrons


Image result for anthracene sign



=14 π electrons

Question24.What do you mean by polynuclear Aromatic Hydrocarbons?

Ans.    Polynuclear hydrocarbons are those hydrocarbons which have two or more rings. These rings may be isolated or fused together

Image result for diphenyl ring Diphenyl                                                   Diphenyl Methane

(isolated ring)                                                                                                      (isolated ring)

Image result for naphthalene sign

                                     Image result for anthracene sign                   

Naphthalene                Anthracene                           Phenanthrene

(fused ring)                 (fused ring)                             (Fused ring)