Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

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.

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. 

Multiple choice chemistry materials of daily use classification of fibres fibres history of fabric

Acrylic is used for making carpets and blankets.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Acrylic fibers are synthetic fibers made from a polymer (polyacrylonitrile) with an average molecular weight of $\sim100,000$, about $1900$ monomer units. Strong and warm, acrylic fiber is often used for sweaters and tracksuits and as linings for boots and gloves, as well as in furnishing fabrics and carpets. It is manufactured as a filament, then cut into short staple lengths similar to wool hairs, and spun into yarn.
option A is correct

Multiple choice chemistry materials of daily use classification of fibres fibres history of fabric

After people began to settle in agricultural communities, they learnt to weave twigs and grass into mats and baskets.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

After people began to settle in agricultural communities, they learnt to weave twigs and grass into mats and baskets. Vines, animal fleece or hair were twisted together into long strands. These were woven into fabrics.

Multiple choice chemistry materials of daily use classification of fibres fibres history of fabric

After people began to settle in agricultural communities, they learnt to weave ____________ and ____________ into mats and baskets.

  1. grass, twigs

  2. cotton, jute

  3. twigs, grass

  4. jute, cotton
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

After people began to settle in agricultural communities, they learnt to weave grass and twigs into mats and baskets.

Multiple choice chemistry materials of daily use classification of fibres fibres history of fabric

In ancient __________, cotton as well as flax were cultivated near the river Nile and were used for making fabrics.

  1. Libya

  2. Egypt

  3. Sudan

  4. Ethiopia
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Egypt is known as the oldest agricultural civilization. Due to less rainfall, river Nile was used as a source of water for agriculture. Hence, in ancient Egypt, cotton as well as flax were cultivated near the river Nile and were used for making fabrics.