Tag: d and f block elements

Quizzes (3) Questions (62)

Questions Related to d and f block elements

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.

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

Which ion is colourless?

  1. $C{ r }^{ +4 }$
  2. $Sc^{ +3 }$
  3. $Ti^{ +3 }$
  4. ${ V }^{ +3 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$(A)$ $Cr\quad [Ar]3d^54s^1$

$Cr^{+4}\quad [Ar]3d^2$
$2$ unpaired $e^-s\longrightarrow$ paramagnetic.

$(B)$ $Sc\quad [Ar]3d^14s^2$
$Sc^{+3}\quad [Ar]3d^2$
$0$ unpaired $e^-s\longrightarrow$ dimagnetic.

$(C)$ $Ti\quad [Ar]3d^24s^2$
$Ti^{+3}\quad [Ar]3d^1$
$1$ unpaired $e^-s\longrightarrow$ paramagnetic.

$(D)$ $V\quad [Ar]3d^34s^2$
$V^{+3}\quad [Ar]3d^2$
$2$ unpaired $e^-s\longrightarrow$ paramagnetic.

Ions which do not have unpaired electrons do not show colour in aqueous solution. These are known as diamagnetic ions.

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

When $MnO _{2}$ is fused with KOH in the presence of air, a coloured compound is formed, the product and its colour is :

  1. $K _{2}MnO _{4}$, dark green
  2. $KMnO _{4}$, purple
  3. $Mn _{2}O _{3}$, brown
  4. $Mn _{3}O _{4}$, black.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The reaction between MnO$ _2$ and KOH in presence of air is given as:

$2MNO _2 +4KOH +O _2$ $\rightarrow$ $2K _2 MnO _4 +2H _2O$
                                         (potassium manganate)
The $K _2Mn O _4$ formed is dark green in colour.

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 elements forms compounds that are all coloured?

  1. Magnesium

  2. Aluminium

  3. Iron

  4. Chromium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Most of the chromium compounds are coloured due to excitation of an electron from a lower energy d-orbital to higher energy d-orbital, the energy of excitation corresponds to the frequency of light absorbed. This frequency lies in a visible region. The colour observed corresponds to the complementary colour of light absorbed.
Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

Which of the following compounds is not colored?

  1. ${Na} _{2}Cu{Cl} _{4}$
  2. ${Na} _{2}Cd{Cl} _{4}$
  3. ${Na} _{3}[Fe{(CN)} _{6}]$
  4. ${K} _{3}[Fe{(CN)} _{6}]$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Electronic configuration: $[Kr] 4d^{10} 5s^{2}$

Cadmium is not considered as transition element which has completely filled d - configuration and is not having unpaired electrons to exhibit color property.
So $Na _2CdCl _4$ do not exhibit color
Hence option B is correct.
Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

Which of the following orbitals are degenerate for $[Cr(H _2O) _6]^{3+}$?

  1. $d _{x^2-y^2},d _{xy}$
  2. $d _{xy},d _{yz}$
  3. $d _{x^2-y^2},d _{yz}$
  4. $d _{z^2},dxy$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:- (B) ${d} _{xy}, {d} _{yz}$

$[Cr(H _2O) _6]^{3+} $ has $d^2sp^3$ hybridization .$dxy,dyz,dzx$,orbitals are degenerate.