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