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 introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Number of $\sigma$ and $\pi$ bonds present in $CH _3-CH=CH- C \equiv CH$ are:

  1. $10\, \sigma,\, 3\, \pi$
  2. $10\, \sigma,\, 2\, \pi$
  3. $9\, \sigma,\, 2\, \pi$
  4. $8\, \sigma,\, 3\, \pi$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sigma bonds are formed by axial overlap and pi bonds are formed by sideways overlap. total number of bonds are $10\, \sigma,\, 3\, \pi$.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

In $N _2$ molecule, the atoms are bonded by:

  1. $1$ $\sigma$ and $2$ $\pi$ - bonds, $2$ L.P.
  2. $1$ $\sigma$ and $1$ $\pi$ - bonds, $1$ L.P.
  3. $2$ $\sigma$ and $1$ $\pi$ - bonds, No L.P.
  4. $1$ $\sigma$, $2$ $\pi$, and No L.P.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
${ N } _{ 2 }$ molecule contains $2$ lone pairs and $1s$ and $2p$ bonds.
$:N\equiv N:$
A triple bond consist of $1$ sigma and two $pi$ bonds. Lone pair refers to a pair of valence electrons that are not shared with another atom, it is also called non-bonding pair.
Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Select the correct statement (s) about the compound $NO[BF _4]$

  1. It has 5$\sigma$ and 2$\pi$ bond
  2. Nitrogen - oxygen bond length is higher than nitric oxide $(NO)$

  3. It is a diamagnetic species
  4. $BF$ bond length in this compound is lower than in $BF _3$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

$NO[BF _4]$ can be separated into $NO^+$ and $BF _4^-$. 
$BF _4^-$ has $4$  bonds, as single bonds between $B$ and $F$.
$NO^+$ has $1$  bonds, $2$ bonds.
It is a diamagnetic species.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

In the cyclo-$S _8$ molecule of rhombic sulphur, all the $S-S$ bond lengths and all the $S-S-S$ bond angles are respectively (give approximate values): 

  1. $204$ pm and $105^{\circ}$
  2. $102$ pm and $120^{\circ}$
  3. $204$ pm and $180^{\circ}$
  4. $102$ pm and $60^{\circ}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There is a single bond between each pair of $S$ atoms and two non-bonding electron pairs on each $S$ atom.Thus we see four electron domains around each $S$ atom and we would expect a tetrahedral geometry corresponding to $sp^3$ hybridisation which gives us the bond angle around $109^0$.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

The number of sigma and pi bonds in the structure:
$CH _2\, =\, CH\, -\, C\, \equiv\, CH$

  1. 7 and 3

  2. 6 and 2

  3. 4 and 3

  4. All are sigma bonds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In $H _{2}C = CH-C\equiv CH$, there are $4: C-H$ sigma bonds and $3: C-C$ sigma bonds, thus it has a total of $7 \sigma$ bonds. Also there are $3 \pi$ bonds in the structure.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

The number of $\sigma$ bonds and $\pi$-bonds present in $\text{pent-4-en-1-yne}$ is:

  1. $10,3$
  2. $4,9$
  3. $3,10$
  4. $9,4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$HC\equiv C-{CH} _{2}-CH={CH} _{2}$


$\text{Pent-4-en-1-yne}$

Triple bond between $C$ and $C$ contains one $\sigma$ bond and two $\pi$ bonds. Double bond between $C$ and $C$ contains one $\sigma$ bond and one $\pi$ bond.

Total $\sigma$ bonds$=10$

Total $\pi$ bonds $=3$

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

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

In which of the following molecules/ions are all the bonds not equal?

  1. $BF _4^-$
  2. $SF _4$
  3. $SiF _4$
  4. $XeF _4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In SF4, the sulfur atom has one lone pair and four bonding pairs (seesaw geometry). Due to the lone pair-bond pair repulsion, the bond lengths are not all equal.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Strength of pi bonds are generally :

  1. stronger than sigma bond

  2. weaker than sigma bond

  3. stronger than ionic bond

  4. weaker than hydrogen bond
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Strength of pi bond is weaker than sigma bond because it is formed due to lateral overlapping of atomic orbitals. 
Since, their is a sharing of electron between the two atoms, which is not in case of hydrogen bond, hence it is stronger than the hydrogen bond.
Ionic bonds are always stronger than the covalent bonds. Since, Pi bonds are covalent bonds hence, it is weaker than ionic bonds.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Pent -2-yne has how many $\sigma$ and $\pi$ bonds?

  1. 10 $\sigma$, 2$\pi$
  2. 12 $\sigma$, 2$\pi$
  3. 15 $\sigma$, 2$\pi$
  4. 13 $\sigma$, 3$\pi$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$CH _3-C\equiv C-CH _2-CH _3$
Pent-2-yne has 12$\sigma$ and 2$\pi$ bonds.
No. of $\sigma$ bonds = $C _1$ has 3 C-H bonds + $C _4$ has 2 C-H bonds + $C _5$ has 3 C-H bonds + 4 C-C bonds = 12$\sigma$ bonds.
No. of $\pi$ bonds = 2 bonds between $C _2$ and $C _3$.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

The correct sequence of bond length in a single bond, a double bond and triple bond of $C$ is:

  1. ${(C - C) = (C = C) = (C \equiv C)}$
  2. ${C \equiv C < C = C < C - C}$
  3. $C - C < C = C < C \equiv C$
  4. $C = C < C \equiv C < C - C$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The bond length changes with the bond order like this:-

$Bond\ length\ \alpha \ \dfrac { 1 }{ Bond\ order } \ \alpha \ \dfrac { 1 }{ No.\ of\ bonds }$

As the number of bonds will increase, the bond order will increase and the bond length will decrease.
So, the correct option is $B$ 
${C \equiv C < C = C < C - C}$

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

$\displaystyle:Mg _{2}C _{3}$ reacts with water forming propyne, $C _{3}^{4-}$ has:

  1. two sigma and two pi bonds

  2. three sigma and one pi bonds

  3. two sigma and one pi bonds

  4. two sigma and three pi bonds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Structure is: $^-C\equiv C-C^{-3}$
So it contains 2 sigma bond and 2 pi bonds.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Which of the following molecule(s) has/have $d _n\, -\, p _{\pi}$ bonding?

  1. $H _2S _2O _3$
  2. $P _4O _{10}$
  3. $SO _3$
  4. $P _4S _{10}$
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

In ${ H } _{ 2 }{ S } _{ 2 }{ O } _{ 3 }$ $S$ empty $d$ orbital and $O$ has electrons in $P$ orbital.

Hence, it has ${ d } _{ n }$$-$${ P } _{ n }$ bonding.
In ${ P } _{ 4 }{ O } _{ 10 }$ $P$ have empty $d$ orbital and $O$ has electrons in $P$ orbital
Hence, it has ${ d } _{ n }$$-$${ P } _{ n }$ bonding.
In ${ SO } _{ 3 }$ $S$ have empty $d$ orbital and $O$ has electrons in $P$ orbital.
Hence, it has ${ d } _{ n }$$-$${ P } _{ n }$ orbital.
Similarly in ${ P } _{ 4 }{ S } _{ 10 }$

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

If "$n$" number of $H _3PO _4$ molecules are polymerized to produce chain molecule and ring molecule separately, then the number of $P - O - P$ linkages formed is, respectively :

  1. $n$ and $(n - 1)$
  2. $(n - 1)$ and $(n - 1)$
  3. $(n - 1)$ and $n$
  4. $n$ and $n$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In case of a ring, the number of linkages will be one less than the number of $P$ atoms because of the fact that each $P$ atom is shared by $2$ rings.
However, in case of a chain no sharing takes place and the number of linkages is equal to $n$.