Chemistry

Chemical Bonding and Molecular Structure

1,277 Questions

This section tests your knowledge of chemical bonding, molecular structure, and hybridization. It covers ionic and covalent bonds, octet rule exceptions, and molecular geometry. These chemistry questions are common in various competitive entrance examinations.

Ionic and covalent bondsHybridisation of elementsOctet rule exceptionsMolecular geometryIntermolecular forces

Chemical Bonding and Molecular Structure Questions

Multiple choice chemistry solid state imperfections in solids

The anionic sites occupied by unpaired electrons are called F-centers or colour centers. They impart ______ $(X)$ colour to the crystals on $NaCl.$ Excess of lithium makes $LiCl$ crystals ______ $(Y)$ and excess of potassium makes $KCl$ crystals ______ $(Z)$. $(X)$, $(Y)$ and $(Z)$ are:

  1. yellow, green and pink respectively.

  2. pink, yellow and violet (or lilac) respectively.

  3. yellow, pink and violet (or lilac) respectively.

  4. red, yellow and pink respectively,
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$NaCl$ shows the metal excess defect, which results in the formation of an F-center in the crystal. When light falls on this crystal, the electron in F-center gets excited. This F-center is then responsible for the yellow $(X)$ color of $NaCl$.

In a similar way, the excess of lithium imparts Pink $(Y)$ colour of $LiCl$ crystals.
In a similar way, the excess of potassium imparts violet/lilac $(Z)$ colour of $KCl$ crystals.

Multiple choice chemistry solid state imperfections in solids

$F-$centres are :

  1. the electrons trapped in anionic vacancies

  2. the electron trapped in cationic vacancies

  3. non-equivalent sites of stoichiometric compound

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$F$-centres or colour centres are points in a crystalline compound at which negative ion missing is replaced by one or more unpaired electrons. 


Hence, they are electrons trapped in anionic vacancies.

Therefore, the option is A.

Multiple choice chemistry solid state imperfections in solids

Each of the following statement is correct except

  1. the lattice positions left vacant by anion and occupied by electrons are called F-centres

  2. the presence of F-centres makes the lattice electrically neutral and diamagnetic

  3. the presence of F-centres gives colour to the crystals

  4. F-centres contain unpaired electrons
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

F-centres contain unpaired electrons, which makes the crystal paramagnetic, not diamagnetic. The other statements are correct descriptions of F-centres.

Multiple choice chemistry chemical bonding and structure formal charge basics of chemical bonding types of bonds

Which has highest specific charge?

  1. $Na^{+}(mass\ no\ =23)$
  2. $Mg^{2+}(mass\ no\ =24)$
  3. $Al^{+3}(mass\ no\ =27)$
  4. $Si^{+4}(mass\ no\ =28)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Specific charge in the ratio of charge of ion to its mass.

Specific charge $=\dfrac { e }{ M } $
For ${ Na }^{ + }=\dfrac { e }{ 23 } ,\quad $ for ${ Mg }^{ 2+ }=\dfrac { 2\times e }{ 24 } $
For ${ Al }^{ 3+ }=\dfrac { 3\times e }{ 27 } ,\quad $ for ${ Si }^{ 4+ }=\dfrac { 4\times e }{ 28 } $
In is in the following order,
${ Si }^{ 4+ }>{ Al }^{ 3+ }>{ Mg }^{ 2+ }>{ Na }^{ + }$

Multiple choice chemistry chemical bonding and structure formal charge basics of chemical bonding types of bonds

In bisulphate ion, the formal charge on sulphur atom is:

  1. $+1$
  2. $+2$
  3. $+4$
  4. $+6$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the bisulphate ion (HSO4-), the sulphur atom is bonded to four oxygen atoms. One oxygen is bonded to hydrogen, and the others are double-bonded or single-bonded with negative charges to satisfy the octet rule, resulting in a formal charge of +2 on the central sulphur atom.

Multiple choice chemistry chemical bonding and structure formal charge basics of chemical bonding types of bonds

Formal charge on nitrogen and oxygen in $NO^- _3$ ion are respectively: 

  1. $0, \dfrac{-1}{3}$
  2. $+1, \dfrac{-1}{3}$
  3. $+1, \dfrac{-2}{3}$
  4. $0, \dfrac{-2}{3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Formula change is basically a change given to an atom, on assuming that the electrons in a chemical bond are shared equally between the atoms, neglecting theirrelative, $EN.$

$FC=V-N-\cfrac{B}{2}$       $(V=\text{no. of valance electron}\N=\text{No. of non bonding electrons}\B=\text{No. of electrons in covalent bond})$
$FC$ on $N$ in $NO^- _3=0$
$FC$ on $O$ in $NO _3^-=\cfrac{-1}{3}$

Multiple choice chemistry chemical bonding and structure formal charge basics of chemical bonding types of bonds

Formal charge on nitrogen in $NO _{3}^{-}$ ion is

  1. $+1$
  2. $+2$
  3. $+5$
  4. $Zero$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the nitrate ion (NO3-), the nitrogen atom is at the center bonded to three oxygen atoms. Using the formal charge formula, nitrogen has 5 valence electrons, 0 lone pair electrons, and 8 bonding electrons (4 bonds), resulting in 5 - 0 - 4 = +1.

Multiple choice chemistry chemical bonding and structure formal charge basics of chemical bonding types of bonds

In the cyanide ion the formal negative charge is on:

  1. $C$
  2. $N$
  3. both $C$ and $N$
  4. resonate between $C$ and $N$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the cyanide ion the formal negative charge resonates between $C$ and $N$. Cyanide ion has resonating structure, $-\overset { \ _ }{ C } \equiv N\longleftrightarrow \overset { \ _ }{ N } \underrightarrow { = } C$