Chemistry

Chemical Compounds and Reactions

329 Questions

Chemical compounds and reactions involve understanding the properties, colors, and formation of various chemical substances. Questions focus on identifying precipitates, observing color changes during reactions, and naming common compounds. This topic is a fundamental part of the chemistry syllabus for competitive exams.

identifying precipitateschemical reaction colorscompound namingcolloidal particle propertiesacid base reactions

Chemical Compounds and Reactions Questions

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

Colour of transition metal ions are due to absorption of some wavelength. This results in:

  1. $d-f$ transition
  2. $s-s$ transition
  3. $s-d$ transition
  4. $d-d$ transition
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Colour of transition metal ions are due to absorption of the same wavelength. This results in $d-d$ transition.

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 ion will give colourless aqueous solution ?  

  1. $Ni^{2+}$
  2. $Sc^{3+}$
  3. $Cu^{2+}$
  4. $Mn^{3+}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:- (B) ${Sc}^{+3}$

Only the ions that have electrons in $d$-orbital and in which $d-d$ transition is possible will be coloured.
Electronic configuration of ${Sc}^{+3} \left( \text{At. no. = 21} \right) - 1 {s}^{2} 2 {s}^{2} 2{p}^{6} 3{s}^{2} 3 {p}^{6}$
Since it do not contains electrons in $d$-orbital and hence will not undergo $d-d$ transition and do not show colour.

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

Why are the compounds of transition metal generally coloured ?

  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
Reveal answer Fill a bubble to check yourself
B,D Correct answer
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.

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

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

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

Transition metals are often coloured.

reason - they frequently posses partially filled of orbitals.

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

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

  1. d-d transition of electrons

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

  4. both (b) and (c)
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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 coloured ?

  1. $ Na _{2}[CuCl _{4}] $
  2. $ Na _{2}[CdCl _{2}] $
  3. $ [Cr(H _{2}O) _{6}]Cl _{3} $

  4. all of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
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 

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

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

  1. L-> M charge transfer transition
  2. $\sigma -{ \sigma }^{ * }$ transition

  3. M-> L charge transfer transition

  4. d-d transition
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

Pair of ions which give blue colour in aqueous state: $V^{+4},\ Ni^{+2},\ Ti^{+3},\ Co^{+2},\ Fe^{+3}\ and\ Cu^{+2}$.

  1. $V^{+4}, Cu^{+2}$
  2. $Co^{+2}, Ni^{+2}$
  3. $Fe^{+3}, Ti^{+3}$
  4. $Co^{+2}, Fe^{+3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

V(4+) (as vanadyl ion) and Cu(2+) (as hydrated copper ion) are well-known for their blue colors in aqueous solutions.

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 are coloured due to charge transfer spectra?

  1. ${K} _{2}{Cr} _{2}{O} _{7}$
  2. $KMn{O} _{4}$
  3. $Cu{SO} _{4}.5{H} _{2}O$

  4. Both (1) and (2)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Both K2Cr2O7 and KMnO4 exhibit color due to charge transfer transitions (LMCT) because the metal centers are in high oxidation states with d0 configurations.

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

The colour imparted by $Co(II)$ compounds to glass is 

  1. green

  2. deep blue

  3. yellow

  4. red
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
 Vanadium yellow-green 
 Chrome emerald green 
 Iron Coke bottle green 
 Manganese amethyst 
 Cobalt violet blue 
 Copper greenish blue to blue 
 Nickel grayish brown 
 Selenium salmon pink 
 Cerium- Titanium yellow 
 Neodymium dichroic violet-pink 
 Uranium yellow (fluorescent