Tag: d and f block elements

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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

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

  1. $Cr{O} _{3}$
  2. ${Cr} _{2}{O} _{3}$
  3. $Cr$
  4. $CrO ({O} _{2})$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $\text{B}$
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 forms a colorless solution in aqueous medium?

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