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 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 $n$.

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 $Fe(CO) _5$, the $Fe-C$ bond possesses:

  1. $\pi$ - character only
  2. both $\sigma$ and $\pi$ - characters

  3. ionic character
  4. $\sigma$ - character only
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
It's called “synergic bonding”. The ligand (CO) donates it's lone pair of electrons to the vacant orbitals of the iron atom and forms the sigma-bond. Since the iron atom also possesses some electrons in it's d-orbitals, it back donates those electrons to the molecular orbitals of the ligand forming a π-bond. In this way, the metal-carbon bond length is reduced and the complex gets more stability. One important thing to keep in mind is that the metal atom donates it's electron pairs to the antibonding MO of CO, so the C-O bond is weakened by this synergic bonding, leading to a larger C-O bond length in the complex (as opposed to a free CO molecule).
Metal-C bond length reduces, C-O bond length increases, complex gets stability.
Hence, option $B$ is correct.
Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

Which of the following is an example of weak electrolyte?

  1. $H _3BO _3$
  2. $H _2SO _4$
  3. $HNO _3$
  4. $HClO _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Boric acid is very weak acid since it dose not give $H^+$ , instead it takes $OH^-$ from $H _2O$ and become $B{ \left( OH \right)  } _{ 4 }^{ - }$ and Proton is lost from $H _2O$ not from boric acid.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

Degree of ionisation does not depend on:

  1. nature of the solvent

  2. nature of the electrolyte

  3. dilution

  4. molecular mass of the electrolyte
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Degree of ionization $(\alpha)$ depends on-

1) Concentration of solute
2) Temperature
3) Nature of electrolysis
4) Nature of solvent
5) Dilution
"$\alpha$" does not depend on molecular mass of electrolyte.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

Two elements have electronegativity of 1.2 and 3.0. Bond formed between them would be ________________.

  1. predominantely ionic

  2. predominantely covalent

  3. co-ordinate bond

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

Difference of electronegativity between the two atoms is 1.8 so the bond would be predominantly ionic and less covalent. For a bond to be 50% ionic and 50% covalent, the difference between electronegativities should be equal to 1.7.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

Which of the following compounds will be dissociated into its constituent ions?

  1. Solid $NaCl$
  2. Molten $NaCl$
  3. Solid $CaCl _2$
  4. Molten $CaCl _2$
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

When electric current is passed through an electrolyte in its molten or aqueous state, the electrolyte is dissociated into its constituent ions.
Molten $NaCl$ breaks down to form $Na^+$ and $Cl^-$ where Sodium transfers its valence electron to Chlorine. So Sodium gets one positive charge and Chlorine gets one negative charge.
Molten $CaCl _2$ breaks down to form $Ca^{2+}$ and two $Cl^-$ ion where Calcium transfers its two valence electron to Chlorine. Hence Calcium gets two positive charges and each Chlorine atom gets one negative charge.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

Which of the following compounds will be dissociated into its constituent ions?

  1. Aqueous $KCl$
  2. Solid $KCl$
  3. Aqueous $MgCl _2$
  4. Solid $MgCl _2$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

When electric current is passed through an electrolyte in its molten or aqueous state, the electrolyte breaks up into its constituent ions.
When aqueous $KCl$ undergoes electrolysis, the ions $K^+$ and $Cl^-$ are formed where potassium transfers its one valence electron to Chlorine. So potassium becomes positively charged and chlorine becomes negatively charged.
When aqueous $MgCl _2$ undergoes electrolysis, the ions $Mg^{2+}$ and two $Cl^-$ ions are formed where magnesium transfers its two valence electron to chlorine. Thus magnesium gets two positive charges and each chlorine gets one negative charge.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

$NaCl \longrightarrow Na^+ +Cl^-$
The above reaction is ionization or dissociation?

  1. Dissociation

  2. Ionization

  3. Both ionization and dissociation

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

Dissociation is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into smaller particles such as atoms, ions or radicals, usually in a reversible manner.

Hence, $ NaCl(aq.)\quad \rightleftarrows \quad { Na }^{ + }(aq.)\quad +\quad { Cl }^{ - }(aq.) $  is a dissociation reaction.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

What is a net ionic equation?

  1. An equation that includes only the substances that are actually participating in the reaction.

  2. An equation that includes all the substances that are in the reaction.

  3. A equation written so that all ions are shown.

  4. An equation written so all charges are balanced on each side.

  5. An equation that includes only ions.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A net ionic equation is an equation that includes only the substances that are actually participating in the reaction.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

Which of the followings is/are dissociation and not ionization?

  1. $H _2O \rightarrow H^+ + OH^-$
  2. $HCl \rightarrow H^+ + Cl^-$
  3. $Cl _2 \rightarrow 2Cl^.$
  4. $KCl \rightarrow K^+ + Cl^-$
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

Dissociation is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into smaller particles such as atoms, ions or radicals, usually in a reversible manner.

$ { Cl } _{ 2 }\rightarrow 2{ Cl }^{ \bullet  } $ - Radical formation is there.

$ KCl\rightarrow { K }^{ + }+{ Cl }^{ - } $ - Ion formation is there.