Chemistry

Chemical Bonding and Molecular Structure

1,420 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 the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Find out the similarities between $I _2Cl _6$ and $Al _2Cl _6$.

  1. Both have $3C\, -\, 4e^-$ bond
  2. Both have $sp^3$- hybridization for the central atom

  3. Both are nonplanar

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

A)  Both $ I _2Cl _6$ and $ Al _2Cl _6$ have $ 3C\, -\, 4e^-$ bonds. Hence, option A is correct.
B) In $ I _2Cl _6$, the central $I$ atom undergoes $sp^3d^2$ hybridization and in $ Al _2Cl _6$, the central $Al$ atom undergoes $sp^3$ hybridization. Thus, the option B is incorrect.
C) $ I _2Cl _6$ is planar and $ Al _2Cl _6$ is non planar. Thus, the option C is incorrect.

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Which of the following molecule has $3C\, -\, 4e^-$ bond?

  1. $Al _2Cl _6$
  2. $Be _2Cl _4$
  3. $I _2Cl _6$
  4. All are having $3C\, -\, 4e^-$ bond
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 $3C-4e^-$ bond is a model used to explain bonding in certain hypervalent molecules such as tetratomic & hexatomic interhalogen compounds, sulphur tetrafluoride, xenon fluoride and the fluoride ions.

$Al _2Cl _6$, $Be _2Cl _4$ and $I _2Cl _6$ contain $3C\, -\, 4e^-$ bond. The chlorine atoms acts as bridges and forms one covalent bond and other coordinate bond.

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Which one of the following methyl diboranes does not exist?

  1. $B _2H _4(CH _3) _2$
  2. $B _2H _3(CH _3) _3$
  3. $B _2H _2(CH _3) _4$
  4. $B _2H(CH _3) _5$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Di borane forms methyl diborane($B _2H _5(CH _3))$,dimethyl diborane($B _2H _4(CH _3) _2$),trimethyl diborane($B _2H _3(CH _3) _3$) ,tetramethyl diborane($B _2H _2(CH _3) _4$).

So $B _2H(CH _3) _5$ can not form,becuase in this compound we have to use bridge hydrogen for the formation of this compound,that never happens.

Hence option D is correct.

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Which of the following overlapping is used for the formation of $3C\, -\, 2e^-$ bond in chain polymer of $BeMe _2$ ?

  1. $sp\, -\, sp\, -\, sp$
  2. $sp^2\, -\, sp^2\,-\, sp^2$
  3. $sp^2\, -\, sp^3\, -\, sp^2$
  4. $sp^3\, -\, sp^3\, -\, sp^3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$sp^3\, -\, sp^3\, -\, sp^3$ overlapping is used for the formation of $3C\, -\, 2e^-$ bond in chain polymer of $BeMe _2$. Thus, the $Be$ atom and $C$ atom of each methyl group is $sp^3$ hybridized.

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Which type of bond is present in $[BeF _2] _n$ polymer?

  1. $3C-2e^-$
  2. $3C-4e^-$
  3. $3C-3e^-$

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$[BeF _2] _n$ contains $3C-4e^-$ bonds.
One $F$ atom and two $Be$ atoms are $3$ centers. The middle $O$ contributes two electrons each to the be atom, thereby a total of $4$ electrons are contributed and it forms $Be−F−Be$ bridges. 

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

In diborane molecule hydrogen bridge bond is formed because boron has:

  1. shortage of 4 electrons required for bonding

  2. shortage of 2 electrons required for bonding

  3. 4 electrons more than required for bonding

  4. 2 electrons more than required for bonding.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  1. The bridge bonds are 3c-2e bonds. They have 2 electrons (4 in normal covalent). Thus in diborane boron is short of 2 electrons hence it forms hydrogen bridge.
Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Identify the statement that is not correct as far as the structure of diborane is concerned: 

  1. there are two bridging hydrogen atoms in

    diborane

  2. each boron atom forms four bonds in diborane

  3. the hydrogen atoms are not in the same plane

    in diborane

  4. all B-H bonds in diborane are similar
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There are 4 2c-2e B-H bonds and 2 3c-2e bonds in diborane.

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron
All the $Al-Cl$ bonds in $Al _2Cl _6$ are equivalent.

  1. True

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

The given statement is False.
All the  $\displaystyle Al-Cl$ bonds in $\displaystyle Al _2Cl _6$ are not equivalent.
Two types of bonds are present in $\displaystyle Al _2Cl _6$, terminal $\displaystyle Al-Cl$ bonds that are normal $\displaystyle 2c-2e$ bonds and $\displaystyle Al-Cl-Al$ bridges that are $\displaystyle 3c-4e$ bonds.

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Which of the following statement is/are correct regarding $B _{2}H _{6}$?

  1. Banana bonds are longer but stronger than normal $B-H$ bonds
  2. $B _{2}H _{6}$ is also known $3c-2e$ compound
  3. The hybrid state of B in $B _{2}H _{6}$ is $sp^{3}$ while that of $sp^{2}$ in $BH _{3}$
  4. It cannot be prepared by reacting $BF _{3}$ with $LiBH _{3}$ in the presence of dry ether
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

In which of the following molecules is hydrogen bond absent?

  1. Water

  2. Inorganic benzene

  3. Diborane

  4. Methanol
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As there is no lone pair of electrons present on the boron in diborane it do not form a hydrogen bond.But in water inorganic benzene and methanol there is a lone pair of electrons on oxygen, nitrogen and oxygen respectively so they form hydrogen bonding between most electronegative atom like nitrogen oxygen and hydrogen.
Hence option $D$ is correct.