Tag: coloured complexes

Questions Related to coloured complexes

Why are the compounds of transition metal generally coloured ?

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

  1. due to s being filled before d (Aufbau principle)

  2. Due to presence of unpaired electron

  3. unfilled d orbital

  4. d-d transition

Show answer
Correct Option: B,D
Explanation:

coloured compound of transition elements is assosiated with partially filled (n-1)d orbitals. the transition metal ions containing unpaired d-electrons undergoes electronic transition from one d-orbital to another. during this d-d transition process the electrons absorb certain energy from the radiation and emit the remainder of energy as colored light. the color of ion is complementary of the color absorbed by it. hence, colored ion is formed due to d-d transition which falls in visible region for all transition elements.

Statement 1: Transition metal compounds are often colored.
Statement 2: They frequently possess partially filled d-orbitals.

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

  1. Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

  2. Both the Statement 1 and Statement 2 are correct, but Statement 2 is NOT the correct explanation of Statement 1.

  3. Statement 1 is correct, but Statement 2 is not correct.

  4. Statement 1 is not correct, but Statement 2 is correct.

Show answer
Correct Option: A
Explanation:

Transition metals are often coloured.

reason - they frequently posses partially filled of orbitals.

Salt of which of the elements are mostly blue in colour ?

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

  1. Cu

  2. Zn

  3. Fe

  4. Cr

Show answer
Correct Option: A
Explanation:

$Cu\longrightarrow $ Blue colour

$Zn\longrightarrow $ White colour
$Fe\longrightarrow $ Green colour
$Cr\longrightarrow $ Orange colour

Colour of $Fe^{+2}$ ions is:

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

  1. blue

  2. light green

  3. very dark green

  4. yellow

Show answer
Correct Option: B
Explanation:

Colour of $Fe^{2+}$ is light green.

Due to this many salts having $Fe^{2+}$ ion are also green in colour.
For ex: $FeSO _4$

The silver salts like $AgBr$ and $AgI$ are coloured because of:

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

  1. d-d transition of electrons

  2. charge transfer

  3. polirisation of halid${Ag}^{+}$ by

  4. both (b) and (c)

Show answer
Correct Option: A
Explanation:

The silver salts like$AgBr$ and $AgI$ are colored, the color of transition metal ions is due  to the presence of unpaired electron . The electrons which absorbs radiations of color that from the visible or UV spectrum and undergo transition from ground state to excited state within d-sub shells,so it is d-d transitions of electrons.

Which of the following compounds is not coloured ?

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

  1. $ Na _{2}[CuCl _{4}] $

  2. $ Na _{2}[CdCl _{2}] $

  3. $ [Cr(H _{2}O) _{6}]Cl _{3} $

  4. all of the above

Show answer
Correct Option: B
Explanation:

The outer shell electronic configuration of $Cu^{2+}$ has $3d^{9}$ configuration and contain 1  unpaired electron, thus it is coloured.

$Na _2[CdCl _2]$, compound is not coloured because of central atom $Cd$ which has $4d^{10} 5s^2$ electronic configuration so transition do not occur.
Hence option B 

The color of $KMn{ O } _{ 4 }$ is due to:

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

  1. L-> M charge transfer transition

  2. $\sigma -{ \sigma }^{ * }$ transition

  3. M-> L charge transfer transition

  4. d-d transition

Show answer
Correct Option: A
Explanation:

The color in $KMnO _4$ arises from an electronic transition.

In the permanganate ion $MnO _4^{-}$, manganese is in the +7 oxidation state, so it has no d electrons. Photons promote an electron from the highest energy molecular orbital to an empty d orbital on the manganese. When a photon of light is absorbed, this charge transfer takes place from L to M.

Choose the correct statement.

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

  1. Only few transition metal complexes are coloured

  2. d-orbital are degenerated hence, they form complexes

  3. Transition metal complexes reflect the complimentary colour of absorbed colour

  4. Energy difference between ${ t } _{ 2(g) }$ and ${ t } _{ g }$ level is very large

Show answer
Correct Option: C
Explanation:

During this d-d transition process, the electrons absorb certain energy from the radiation and emit the remainder of energy as colored light. The color of ion is complementary of the color absorbed by it. hence, colored ion is formed due to d-d transition which falls in the visible region for all transition elements.

Which of the following  is expected to form colourless complex?

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

  1. ${ Ni }^{ 2+ }$

  2. ${ Cu }^{ + }$

  3. ${ Ti }^{ 3+ }$

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

Show answer
Correct Option: B
Explanation:
$Cu^+$ is colourless 
D block elements of periodic table are called as Transition elements. Transition elements have partially filled d orbitals. The colour for the elements of D block is due to transition of electrons which is called as  d -Transition for which presence of partially filled d electrons is must.
copper  Cu , has 29 electrons. 
so  electronic configuration will be $1s^22s^22p^63s^23p^64s^13d^{10}$
but in case of $Cu^+$ ion, 28 electrons so:
electronic configuration will be $1s^22s^22p^63s^23p^63d^{10}$
$Cu^+$ ion will loose its $4s^1$ electron,  and as it has filled $3d^{10}$ orbital,therefore no transition  and hence $Cu^+$ ion will not have any colour.


Out of $TiF _{6}^{2-},\ CoF _{6}^{3-},\ Cu _{2}Cl _{2}$ and $NiCl _{4}^{2-}$, the colourless sphere are..... 

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

  1. $Cu _{2}Cl _{2},\ NiCl _{4}^{2-}$

  2. $TiF _{6}^{2-},\ Cu _{2}Cl _{2}$

  3. $CoF _{6}^{3-},\ NiCl _{4}^{2-}$

  4. $TiF _{6}^{2-},\ CiF _{6}^{3-}$

Show answer
Correct Option: B