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 p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Which molecule is relatively more stable?

  1. $O _2$
  2. $H _2$
  3. $Li _2$
  4. $N _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nitrogen molecule ($\displaystyle N _2$) is relatively more stable. Each $N$ atom has completed its octet and there is a triple bond between two $N$ atoms. In other molecules, there is either a single bond or a double bond between two atoms. A triple bond is stronger than a single or double bond.

Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

The single $X-X$ bond made by $N$ is weaker than that of $P$ because:

  1. of repulsion between nitrogen nucleus due to smaller size of nitrogen atom

  2. of repulsion between non-bonded electrons due to smaller size of nitrogen atom

  3. of higher bond enthalpy of nitrogen

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

The single $N-N$ bonds formed is weaker than single $P-P$ bonds because of lone pair repulsion on small nitrogen molecule.

Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Which of the following do have $p _{\pi}$ - $d _{\pi}$ bonding?

  1. $NO^- _3$
  2. $SO^{-2} _3$
  3. $BO^{-3} _3$
  4. $CO^{-2} _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$p\pi-d\pi$ bonding includes d-orbitals,if you observe the options only S belongs to $3^{rd}$ period and has d-orbitals(though unoccupied in ground state).

Other options $C$ and $N$ belongs to $2^{nd}$ period while B belongs to $1^{st}$ period and doesn't have d-orbitals.

Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Single $N-N$ bond is weaker than the single $P-P$ bond. This is because of:

  1. larger $N-N$ bond length in comparison to $P-P$ bond length
  2. high interelectronic repulsion of the non-bonding electrons, owing to the small $N-N$ bond length in comparison to that in $P-P$ single bond
  3. higher electronegativity of $N$ in comparison to $P$
  4. smaller atomic size of $N$ as compared to that of $P$
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

$N-N$ single bond is weaker than $P-P$ bond due to smaller size of $N$ as compared to $P$. Smaller size of $N$ leads to smaller $N-N$ bond length. As a result, the lone pair of electrons on the both the $N$ atoms repel each other leading to unstability or weakening of $N-N$ bond. Because of larger size of $P$ atom, $P-P$ bond length is more and lone pair-lone pair repulsion between $P$ atoms is less which makes the $P-P$ bond stronger than $N-N$ bond.

Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Which of the following halide of nitrogen is unstable in nature?

  1. $NCl _3$
  2. $NBr _3$
  3. $NI _3$
  4. $NF _3$
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Nitrogen has very small size as compared to the halogens, which have much larger sizes. Due to this, they can not remain bonded to the nitrogen atom and hence are highly unstable. $NF _3 $ is stable because fluorine and nitrogen have comparable sizes and electronegativity.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Lithium salts are mostly hydrated like $ LiCl.2H _2O $ due to:

  1. maximum ionisation enthalpy
  2. maximum degree of hydration of $Li^+$

  3. maximum hydroscopic nature

  4. maximum chemical reactivity.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$ { Li }^{ + } $ ion being small in size is surrounded by large no. of water molecules on account of which it has very hydration energy. Hence, it is heavily hydrated and have high degree of hydration.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

What is the correct formula for lithium fluoride?

  1. $LiF$
  2. ${Li} _{2}{F} _{2}$
  3. ${Li} _{3}{F} _{9}$
  4. $Li{F} _{7}$
  5. ${Li} _{7}{F} _{19}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$LiF$ is the correct formula for lithium fluoride. $Li$ has a +1 charge and $F$ has a -1 charge so, when they come together, to form $LiF$ having an ionic bond. 

Multiple choice chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

Which substance would have the lowest melting point?

  1. ${ Mg } _{ 3 }{ Al } _{ 2 }$
  2. $Ca{ Cl } _{ 2 }$
  3. ${ Cu } _{ 2 }Sn$
  4. ${ C } _{ 12 }{ H } _{ 22 }{ O } _{ 11 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$C _{12}H _{22}O _{11} (Sucrose) -180^{\circ}C$

$Mg _{3}Al _{2}, CaCl _{2}$ and $Cu _{2}S _{n}$ show ionic bonding where as $C _{12}H _{22}O _{11}$ show covalent bonding. And we know melting point of covalent bonded compound is less then ionic compound.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Affinity for hydrogen decreases in the group from fluorine to iodine. Which of the halogen acids should have highest bond dissociation enthalpy? 

  1. $HF$
  2. $HCl$
  3. $HBr$
  4. $HI$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
As the size of the halogen atom decreases the bond length between halogen and hydrogen decreases ,So the bond becomes stronger and hence the energy required to break the bond ( bond dissociation enthaphy) increases.

So the compound with highest bond dissociation energy is $HF$

Hence option A is correct.
Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Less ionic compound among the following

  1. NaF

  2. KCl

  3. KF

  4. NaCl
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

According to Fajan's rules, larger cations and smaller anions favor covalent character, while smaller cations and larger anions favor ionic character. Sodium chloride (NaCl) has a smaller anion compared to fluorides, making it relatively less ionic among the given alkali halides.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Compare oxygen and flourine in Ionic radius$\quad O^{2-} , F^-$:

  1. $\space O^{2-} = F^-$
  2. $\space O^{2-} < F^-$
  3. $\space O^{2-}> F^-$
  4. $\space O^{2-} \geq F^-$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Among the elements of same period the ion with more number of electrons and less number of protons is having more radius.If the number of electrons are same the ion with less number of protons is having more radius.

Here $\quad O^{2-} $and $ F^-$ both are having same 10 electrons but oxygen is having 8 protons(which can atrract outer electrons with less force than florine) and florine is having 9 protons.So the ionic radius of $\space O^{2-}>  F^-$

Hence option C is correct.