Chemquiz

Q.1 The structure of CaB₆ is close to that of
       A.Cesium chloride
       B.Nickel arsenide
       C.Rock salt
       D.Zink blende

Answer:-A
Explanation:-The calcium atoms are arranged in simple cubic packing so that there are holes between groups of eight calcium atoms situated at the vertices of a cube. The simple cubic structure is expanded by the introduction of the octahedral B₆ groups and the structure is a CsCl-like packing of the calcium and hexaboride groups. Another way of describing calcium hexaboride is as having a metal and a B₆²⁻ octahedral polymeric anions in a CsCl-type structure were the Calcium atoms occupy the Cs sites and the B₆ octahedra in the Cl sites The Ca-B bond length is 3.05 Å and the B-B bond length is 1.7 Å.

Q.2 Dinuclear  anion [I₂(OH)₂O₈]⁴⁻ has two bridging oxo groups.The geometry around each iodine         is
      A.octahedral
      B.monocapped octahedral
      C.square pyramidle
      D.pentagonal bipyramidle
Ansewer:-A
Explanation:--Central element is Iodine.
                      -All ligands should be equally distributed between two Iodine.
                      -Two oxygen are presents as oxo (bridging) groups.
                      -Rest 6 oxygen will be as three to each iodine.
 The structure of these compound is octahedral.

Q.3 Using a double beam U-V visible spectrophotometer Beer's law fails for K₂Cr₂O₇ solution when
       A.Intensity of light source is changed
       B.Detector is not a photomultiplier tube
       C.Cuvette of 2cm size is used
       D.pH is not kept same in all measurement
Answer:-D
Explanation:--Beer's law is given as
                        A=εcl
                      ε = molar absorbtibility ,
                      c = concentration of compound,
                      l = path lenth
- K₂Cr₂O₇ contain dichromate ion Cr₂O₇²⁻
-The ions are less basic
-Increase in pH will increase the basisity of compound.
-In solution......Cr₂O₇²⁻ + 2H₂O⟶ 2CrO⁴⁻ + 2H⊕
-According to Le-chetellier's principle increase pH will increase no. of  H⊕ ion and equilibrium will shift right side.
-more chromate ion will form.

Q.4 Trivalent lanthenide ion having isotropic magnetic susceptibility is
     A.Eu3+
     B.Gd3+
     C.Yb3+
     D.Lu3+
Answer:-B

Q.5 Among the elements Zn,Ga,Ge and As,the one with the lowest first ionization energy is
      A.As
      B.Zn
      C.Ga
      D.Ge
Answer:-C

Physical chemistry quiz

Q.1 In order to increase the volume of a gas by 10%, the pressure of the gas should be
      A. increased by 10 %
      B. increased by 1 %
      C. decreased by 10 %
      D. decreased by 1 %
 
Answer:-C
Explanation:-Boyle measured the volumes of gases at different pressures. Boyle found that when the pressure of gas at a constant temperature is increased, the volume of the gas decreases. when the pressure of gas is decreased, the volume increases. this relationship between pressure and volume is called Boyle's law
.
Q.2 Which one of the following is not a perfect differential ?
       A.dG
       B.dT
       C.dQ
       D.dH
Answer:-C
Explanation:-dU, dG, dH etc are all exact differentials and the variables themselves are known as state functions because they only depend on the state of the system. However, dq and dw for example, are inexact differentials. Exact differentials are not dependent on the path but inexact differentials are.

Q.3 Reverse Osmosis is an example of
      A.Reversible process
      B.Irreversible process
      C.Equilibrium process
      D.Non-spontaneous process
Answer:-D

Chem quiz

Q.1  A reaction involving two different reactants can never be
       (a) Unimolecular reaction
       (b) First order reaction
       (c) second order reaction
       (d) Bimolecular reaction



Answer (a) Unimolecular reaction

Q.2 Due to the presence of an unpaired electron, free radicals are:
      (a) Chemically reactive
      (b) Chemically inactive
      (c) Anions
      (d) Cations

Answer (a) Chemically reactive

Q.3 Lattice energy of an ionic compounds depends upon
      (a) Charge on the ion only
      (b) Size of the ion only
      (c) Packing of ions only
      (d) Charge on the ion and size of the ion

Answer (d) Charge on the ion and size of the ion

Q.4 The highest electrical conductivity of the following aqueous solutions is of

      (a) 0.1 M acetic acid
      (b) 0.1 M chloroacetic acid
      (c) 0.1 M fluoroacetic acid
      (d) 0.1 M difluoroacetic acid

Answer (d) 0.1 M difluoroacetic acid

Q.5 During the process of electrolytic refining of copper, some metals present as impurity settle as           ‘anode mud’ These are

     (a) Sn and Ag
     (b) Pb and Zn
     (c) Ag and Au
     (d) Fe and Ni

Answer (c) Ag and Au

Chem quiz

Q.1 The water exchange rates for the complex ions follow the order

         (A) [V(H2O)6]2+ > [Co(H2O)6]2+ > [Cr(H2O)6]3+

         (B) [Cr(H2O)6]3+ > [Co(H2O)6]2+ > [V(H2O)6]2+

         (C) [Co(H2O)6]2+ > [Cr(H2O)6]3+  > [V(H2O)6]2+

         (D) [Co(H2O)6]2+ > [V(H2O)6]2+ > [Cr(H2O)6]3+

Ansewr:-D 

Q.2 Based on Wade’s rule, the structure-type of [B₅H₈]⁻ is
        (A) closo
        (B) nido
        (C)  arachno
        (D)  hypho

Ansewr:-B

Q.3  The coordination geometries around the copper ion of plastocyanin (a blue-copper protein) in              oxidized and reduced form, respectively, are
         (A) tetrahedral and square-planar
         (B) square-planar and tetrahedral
         (C) distorted tetrahedral for both
         (D) ideal tetrahedral for both

Answer:-C

Chem quiz

Q.1 Mention the formula to calculate pH of a solution?

 Answer:- In order to calculate the pH of a solution you have to use the formula pH= -log [H+] or pH                    = -log [H3O+]

Q.2 Mention how many millilitre is equal to 1 litre and how many microliter is equal to litre?
Answer:-  1 millilitre = 0.0001 litre
                 1 microliter = 0.0000001 litre

Q.3 Explain what is titration?

Answer:- Titration is a process to determine the molarity of a base or an acid. In this process a reaction is carried out between the known volumes of a solution with a known concentration, against the known volume of a solution with an unknown concentration.

Organic quiz

Q.1 Phenol, when it first reacts with concentrated sulphuric acid and then with concentrated nitric              acid, gives
      (a) 2,4,6-trinitrobenzene
      (b) o-nitrophenol
      (c) p-nitrophenol

      (d) nitrobenzene

Explanation:-

Sulfonation
The reaction of phenol with concentrated sulfuric acid is thermodynamically controlled. At 25°C, the ortho product predominates while at 100°C, the para product is the major product.

Notice that at both 25° and 100°, initially an equilibrium is established. However, at the higher temperature, the equilibrium is destroyed and the more thermodynamically stable product is produced exclusively.

Nitration

Phenol, when treated with dilute nitric acid at room temperature, forms ortho‐ and para‐nitrophenol

Answer (b) o-nitrophenol

Q.2  α-D-(+)-glucose and β-D-(+)-glucose are
       (a) conformers
       (b) epimers
       (c) anomers

       (d) enantiomers

Explanation:-

Anomers are stereoisomers of cyclic sugars that differ in configuration only at the hemiacetal or hemiketal carbon.

Glucose is both an aldehyde at C-1 and an alcohol at C-5. These two groups can react with each other to form a cyclic hemiacetal (glucopyranose).

www2.chemistry.msu.edu

In the hemiacetal, C-1 has become chiral. It can have the OH group either "down" or "up". These two isomers are anomers, and C-1 (the original carbonyl carbon) is the anomeric carbon.

Answer (c) anomers

Q.3 HBr reacts with CH2 = CH – OCH3 under anhydrous conditions at room temperature to give
      (a) CH3CHO and CH3Br
      (b) BrCH2CHO and CH3OH
      (c) BrCH2 – CH2 – OCH3

      (d) H3C – CHBr – OCH3

Explanation:-

Methyl vinyl ether is a very reactive gas. It is hydrolysed rapidly by dilute acids at room temperature to give methanol and aldehyde.

However, under anhydrous conditions at room temperature, it undergoes many addition reactions at the double bond.

Answer (d) H3C – CHBr – OCH3

Basic quiz

Q.1 An atom has 2 electrons in K-shell, 8 electrons in L-shell and 6 electrons in M-shell. The number       of S-electrons present in the element is:

      A.6
      B.4
      C.10

      D.9

Answer:-6

Q.2 The Boltzmann constant K is equal to:
      A. N/R
      B. R/N
      C. 1/NR
      D. NR

Answer:-B


Q.3 Rutherford’s scattering experiment is related to:
      A. Neutron
      B. Nucleus
      C. Proton
      D. Electron

Answer:-B