Tag: d and f block elements

Questions Related to d and f block elements

Ammonium dichromate is used in fire works. The green colored powder blow in the air is:

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

  1. $Cr{O} _{3}$

  2. ${Cr} _{2}{O} _{3}$

  3. $Cr$

  4. $CrO ({O} _{2})$

Show answer
Correct Option: B
Explanation:
$(\mathrm{NH} _4) _2\mathrm{Cr} _2\mathrm{O} _7\xrightarrow{\Delta} \mathrm{Cr} _2\mathrm{O} _3+\mathrm{N} _2+4\mathrm{H} _2\mathrm{O}$

The green-coloured $ Cr _2O _3$ powder is blown in the air by the large volume of $ N _2$ and water vapour produced and settles like dust from the volcano. 

Hence, the correct option is $\text{B}$

Which one of the following forms a colorless solution in aqueous medium?

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

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

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

  3. ${Sc}^{3+}$

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

Show answer
Correct Option: C
Explanation:

$Cr^{3+}$ = $3d^3$ = coloured

$Ti^{3+}$ =  $3d^1$ = coloured

$V^{3+}$ =  $3d^2$ = coloured

$Sc^{3+}$ has electron configuration of [Ar] $4s^0  3d^0$. Therefore without any unpaired electrons it forms a colorless solution in aqueous medium.