Tag: coloured complexes

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Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

Which one of the following ionic species will not impart color to an aqueous solution?

  1. ${Ti}^{4+}$
  2. ${Cu}^{+}$
  3. ${Zn}^{2+}$
  4. ${Cr}^{3+}$
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation
The transition metal ions which have completely filled d-orbitals are colorless.

The transition metal ions which have completely empty d-orbitals are also colorless.

$ Cr^{3+}$ has a blue-green color.  because contain unpair electrons.

Rest all are colorless. 
Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

The colorless species is:

  1. $V{Cl} _{3}$
  2. $VO{SO} _{4}$
  3. ${Na} _{3}{VO} _{4}$
  4. $\left[ V{ \left( { H } _{ 2 }O \right) } _{ 6 }{ SO } _{ 4 } \right] .{ H } _{ 2 }O$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$ VCl _3$ is green.

 
$ VOSO _4$ is blue. 

$ Na _3VO _4$ is colorless vanadium is present in +5 oxidation state .it does not have any unpaired electron.
 
$\left[ V{ \left( { H } _{ 2 }O \right)  } _{ 6 }{ SO } _{ 4 } \right]$ .${ H } _{ 2 }O$ is purple.

Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

The aqueous solution of the salt will colored in the case of:

  1. $Zn{({NO} _{3})} _{2}$
  2. $Li{NO} _{3}$
  3. $Co{({NO} _{3})} _{2}$
  4. $Cr{Cl} _{3}$
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

$ Co^{2+}$ = $3d^7$  


$Cr^{3+}$ = $3d^3$
 
$ Co^{2+}$ and $Cr^{3+}$   will have unpaired electrons and hence are expected to have aqueous solution of the salt colored.

Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

What is/are true statement?

  1. Ions of $d$-block elements are colored due to $d-d$ transition
  2. Ions of $f$-block elements are colored due to $f-f$ transtition
  3. ${ \left[ Sc{ \left( { H } _{ 2 }O \right) } _{ 6 } \right] }^{ 3+ },{ \left[ Ti{ \left( { H } _{ 2 }O \right) } _{ 6 } \right] }^{ 4+ }$ are colored complexes.
  4. ${Cu}^{+}$ is colorless ion.
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation
$Cu^+$ is colourless because it doesn't contain any electrons which can absorb light. .

In ${ \left[ Sc{ \left( { H } _{ 2 }O \right)  } _{ 6 } \right]  }^{ 3+ }$, $ Sc^{3+}$  is $ d^0$ system and hence colorless.

Hence,option C is incorrect.
Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

The aqueous solutions of the following salts will be colored in the case of:

  1. $Zn{({NO} _{3})} _{2}$
  2. $Li{NO} _{3}$
  3. $Co{({NO} _{3})} _{2}$
  4. $Cr{Cl} _{3}$

  5. Potash alum
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation
${Co}^{2+}$
$\uparrow \downarrow $ $\uparrow \downarrow $ $\uparrow $ $\uparrow $ $\uparrow $
$z=27$
$Co=[Ar]{3d}^{7}{4s}^{2}$
${Co}^{2+}=[Ar]{3d}^{7}$
Two unpaired electrons present.

${Cr}^{3+}$:
$z=24$
$Cr=[Ar]{3d}^{5}{4s}^{1}$
${Cr}^{3+}=[Ar]{3d}^{3}$
$\uparrow $ $\uparrow $ $\uparrow $
$Co{({NO} _{3})} _{2}$ and $Cr{Cl} _{2}$ have unpaired electron; hence, they are colored.

The compounds have $ Zn^{2+}, Li^+, Co^{2+} and Cr^{3+}$ with 0, 0, 2 and 3 unpaired electrons. Hence option C and D are correct. Potash alum is colorless. 
Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

Out of the ions $Ag^+, Co^{2+}, Ti^{4+}$, which one will be coloured in aqueous solutions.


[Atomic no : Ag = 47, Co = 27, Ti = 22]

  1. $Ag^+$
  2. $Co^{2+}$
  3. $Ti^{4+}$

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

compound with unpaired d-electron will show color.


$Ag^+ = 5d^{10} \,\,\,\,\,\,,n = 0$

$Ti^{+4} = 3s^2 3p^6 \,\,\,\,\,\,, n = 0$

$Co^{+2} = [Ar]3d^7\,\,\,\,\,\,\,,n = 3$ It will show color due to unpaired d electrons.

Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

Most copper $(I)$ compounds are found to be colourless. This is due to :

  1. presence of low oxidation state of copper
  2. completely filled d-level in $Cu(I)$

  3. diamagnetic nature of the compound
  4. high polarizability of $Cu(I)$ ion
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In copper (I) ion there are no vacant d orbitals as it is diamagnetic. Copper(I) ion being less charged has small ligand field effect and the transition is in the infrared region in which no color is perceived by human eye.

Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

The ion which exhibits green colour is:

  1. $Cu^{2+}$
  2. $Mn^{2+}$
  3. $Co^{2+}$
  4. $Ni^{2+}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Transition metal ion                     Colour

            ${ Cu }^{ 2+ }$                                blue-green
            ${ Fe }^{ 2+ }$                                 olive green
            ${ Ni }^{ 2+ }$                                  bright green
            ${ Fe }^{ 3+ }$                                 brown to yellow
${ Ni }^{ 2+ }$ only exhibits green colour, other exhibits partial green colours / mixed green colours.