Tag: coloured complexes

Questions Related to coloured complexes

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

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

  1. ${Ti}^{4+}$

  2. ${Cu}^{+}$

  3. ${Zn}^{2+}$

  4. ${Cr}^{3+}$

Show answer
Correct Option: A,B,C
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. 

The colorless species is:

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

  1. $V{Cl} _{3}$

  2. $VO{SO} _{4}$

  3. ${Na} _{3}{VO} _{4}$

  4. $\left[ V{ \left( { H } _{ 2 }O \right) } _{ 6 }{ SO } _{ 4 } \right] .{ H } _{ 2 }O$

Show answer
Correct Option: C
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.

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

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

  1. $Zn{({NO} _{3})} _{2}$

  2. $Li{NO} _{3}$

  3. $Co{({NO} _{3})} _{2}$

  4. $Cr{Cl} _{3}$

Show answer
Correct Option: C,D
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.

What is/are true statement?

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

  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.

Show answer
Correct Option: A,B,D
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.

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

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

  1. $Zn{({NO} _{3})} _{2}$

  2. $Li{NO} _{3}$

  3. $Co{({NO} _{3})} _{2}$

  4. $Cr{Cl} _{3}$

  5. Potash alum

Show answer
Correct Option: C,D
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. 

The ion that gives colourless compound:

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

  1. $Sc^{+3}$

  2. $V^{+3}$

  3. $Cr^{+3}$

  4. All of these

Show answer
Correct Option: A

Which pair of ions is colourless.

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

  1. $Mn^{+3}, CO^{+3}$

  2. $Fe^{3+}, Cr^{+3}$

  3. $Zn^{2+}, Sc^{3+}$

  4. $Ti^{2+}, Cu^{2+}$

Show answer
Correct Option: C
Explanation:

As both $Zn^{2+}  = d^{10}, Sc^{3+} = d^0$ have zero unpaired d-electron so they both are colourless.

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]

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

  1. $Ag^+$

  2. $Co^{2+}$

  3. $Ti^{4+}$

  4. None of these

Show answer
Correct Option: B
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.

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

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

  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

Show answer
Correct Option: B
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.

The ion which exhibits green colour is:

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

  1. $Cu^{2+}$

  2. $Mn^{2+}$

  3. $Co^{2+}$

  4. $Ni^{2+}$

Show answer
Correct Option: D
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.