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 Multiple Choice QuestionsMultiple Choice Questions

1.

Which of the following element does not show variable valency ?

  • Ni

  • Zn

  • Cu

  • Mn


B.

Zn

The electronic configuration of Zn is [Ar]3d10, 4s2. Hence, due to complete d- subshell, it does not show' variable valency. It shows only +2 valency.


2.

Which of the following dissolves in hot conc. NaOH solution?

  • Fe

  • Zn

  • Cu

  • Ag


B.

Zn

Zinc dissolves in hot conc. NaOH solution. It is a reactive metal. It dissolves in excess of hot NaOH to give sodium zincate.

Zn + 2NaOH Na2ZnO2 + H2 sodium zincate 


3.

Lanthanide for which +II and +III oxidation states are common is

  • La

  • Nd

  • Ce

  • Eu


D.

Eu

Europium or Eu has +II and +III oxidation states common as lanthanide.


4.

The general electronic configuration of transition elements, is :

  • (n-1)d1-5 ns0

  • (n-1)d1-10 ns1

  • (n-1)d1-10 ns2

  • (n-1)d1-10 ns1-2


D.

(n-1)d1-10 ns1-2

The general electronic configuration of transition elements is (n-1)d1-10 ns1-2


5.

The compound used for gravimetric estimation of copper(II) is

  • Cu2(SCN)2

  • Cu2O

  • Cu2I2

  • Cu2CO3


A.

Cu2(SCN)2

Copper thiocyanate or Cu2(SCN)2 is used to estimate copper gravimetrically.

2Cu2+ + SO42- + 2SCN + H2O → 2CuSCN + H2SO4


6.

Assertion: Cuprous ion (Cu+) is colorless whereas cupric ion (Cu2+) is blue in the aqueous solution.
Reason: Cuprous ion (Cu+) has unpaired electrons while cupric ion (Cu2+) does not.

  • If both assertion and reason are true and reason is a correct explanation of the assertion.

  • If both the assertion and reason are true but the reason is not a correct explanation of the assertion.

  • If the assertion is true but the reason is false.

  • If both the assertion and reason are false.


C.

If the assertion is true but the reason is false.

Cuprous ions (Cu+) is colourless because it has no unpaired electrons in the 3d sub-shell as it has 3d configuration. The cupric ion (Cu2+) has one unpaired electron as it has configuration 3d10. By absorbing the visible light, the unpaired electron can migrate from one set of d-orbitals to another under the applied field of water molecules. Hence, cupric ion (Cu2+) in aqueous solution shows a blue colour.


7.

Which of the following turns potassium dichromate paper green?

  • NO2

  • HCl

  • NH3

  • SO2


D.

SO2

SO2 gas is a reducing agent, hence turns dichromate paper green due to formation of chromium sulphate. Sulphite radical (SO32- is identified by this:

K2Cr2O+ 3SO2 + H2SO4 Cr2(SO4)2 + K2SO4 + H2O


8.

The transition metals mostly are

  • paramagnetic

  • diamagnetic

  • both 'a' and 'b'

  • neither diamagnetic nor paramagnetic


A.

paramagnetic

Most of the transition metals show paramagnetic behaviour. The unpaired electrons in (n - 1)d orbitals are responsible for the magnetic properties.


9.

The 3rd transitional series contain elements having atomic numbers from:

  • 21 to 29

  • 21 to 30

  • 20 to 30

  • 21 to 31


B.

21 to 30

The third transitional series contain elements having atomic numbers from 21 to 30.


10.

Transition metals are related to which block ?

  • 's' block

  • 'p' block

  • 'd' block

  • none of these


C.

'd' block

d-block elements are called transition elements. These show variable valency due to their incomplete d-subshell.