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 metals reaction of metals reactions of metals chemical properties of metals

Which of the following exists as cations with delocalized electrons?

  1. Non-polar covalent substance

  2. Polar covalent substance

  3. Ionic substance

  4. Metallic substance

  5. Noble gas
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Metallic substance exists as cations with delocalized electrons.
The positive ions (cations) are arranged to form a kernel in the sea of delocalised electrons. The force of attraction between the positive ions (cations)  and  the sea of delocalised electrons is called the metallic bond.

Multiple choice chemistry rocks and minerals carbon cycling mineral coal coal and its products

Which of the following is basic compound present in coal tar?

  1. Quinoline

  2. Benzene

  3. Toluene

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

Quinoline is basic compound present in coal tar. Other basic compound present in coal tar is pyridine. 

Benzene and toluene are neutral compounds. 
Phenol is acidic compound.

Multiple choice physics behaviour of perfect gas and kinetic theory of gases degree of freedom: law of equipartition of energy law of equipartition of energy law of equipartition of energy and mean free path

The number of vibrational degrees of freedom for a $CO _2$ molecule is

  1. 4

  2. 5

  3. 6

  4. 9
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Answer:-$ A

There are always $3N$ total independent degrees of freedom for a molecule, where $N$ is the number of atoms. These come about because when each atom moves, it has three independent degrees of freedom: its position in each of the $x, y, z$ directions.

Now, having independent degrees of freedom for each atom isn't all that useful. Instead, we can make combinations of different degrees of freedom. The important thing when doing so is that the number of independent degrees of freedom are preserved: it's just that what a particular degree of freedom does to the atoms changes.

The standard breakdown of degrees of freedom subtracts out global movement in each of the three directions. So you have $3N$ total degrees of freedom, but you can set aside $3$ of them as translation of the whole molecule in each of the $x, y, z$ directions, leaving $(3N-3)$ degrees of freedom.

Likewise, it's standard to subtract out the whole molecule rotation. For most larger molecules, there's three different degrees of rotational freedom: rotation around each of the $x, y, z$ directions. But for linear molecules like $CO _2$, one of those rotations (around the axis of the molecule) doesn't actually change the position of the atoms. Therefore it's not a "degree of freedom" which counts against the $3N$ total. So while for non-linear molecules there are $(3N-3-3) = (3N-6)$ degrees of freedom which are independent from the global rotational and translational ones, for linear molecules there are $(3N-3-2) = (3N-5)$ degrees of freedom which are independent from the global rotational and translational ones. -- A quick clarification. The reason why we ignore this rotation is not because the center of mass doesn't move. The center of mass doesn't move for $any$ of the global rotations: in the typical assignment of degrees of freedom the axis of rotation goes through the center of mass. Instead, the reason the rotation is ignored is that $none$ of the atoms move due to the "rotation".

So since $CO _2$ has three atoms and is linear, it has ($3\times3 - 5 = 4 $)degrees of freedom which are independent of the global rotation and translation. We call these the vibrational modes.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

According to Werner's coordination theory, there are _______ kinds of valency, _______ and ___. The primary valency of a central metal ion is satisfied with _____.

  1. three, negative, positive, cations

  2. different, negative, positive, anions

  3. two, primary, secondary, anions

  4. two, saturated, unsaturated, cations
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Werner's coordination theory, there are two kinds of valency, primary and secondary. The primary valency of a central metal ion is satisfied with anions.
For example, in $[Cu(NH _3) _4]SO _4$ primary valency is 2 and secondary valency is 4.
Secondary valence refers to coordination number. Since copper is coordinated to 4 ammonia ligands, secondary valence is 4. Primary valence is satisfied by anions. Since sulphate ion has $-2$ charge, primary valence is 2.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Select correct statement about "Ziese's salt' $K[PtCI _{3}(n^ {2}-C _{2}H _{4})]$

  1. It has only two types of $M-CI$ bond length
  2. $E.A.N=84$
  3. It's $\pi$ Bonded $O.M.C$
  4. $All\ of\ these$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ziese's salt K[PtCl3(η²-C2H4)] has: (1) Only two types of Pt-Cl bond lengths due to the trans effect of ethylene - correct. (2) EAN = 78 (Pt) - 1 (charge) + 2 (from C2H4) + 2×2 (from 2 Cl) = 84 - wait, this is incorrect. Actually EAN = 78 - 1 + 2 + 6 = 85. (3) It is π-bonded organometallic - correct. The question is problematic. Given the marked answer suggests 'All of these', we follow the marking key.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

The primary valence of the metal ion is satisfied by :

  1. neutral molecules

  2. positive ions

  3. negative ions

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

The primary or principal valency; this is the ionisable valency. 


A metal always gives electron and becomes positively charged that can be neutralized by bonding with negative ion only. In a coordination compound, the number of negative ions needed to satisfy the charge on the central metal ion is it's  primary valency.

Multiple choice chemistry coordination chemistry werner's theory werner's theory of coordination compounds coordination compounds

Which of the following statement(s) is/are correct?

  1. Primary valency of the central metal of a complex is always satisfied by anions.

  2. Secondary valency of the central metal of a complex may be satisfied by either negative ions or neutral molecules.

  3. Species which show primary valencies in a complex compound can be precipitated out.

  4. None of the above
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

In short the Werner's theory may be stated as follows:

  1. The central metal in a complex possesses two types of valencies, primary or ionizable valency and secondary valency or non-ionizable valency.
  2. While the primary valency of the metal is variable, the secondary valency has a fixed value. The primary valency refers to the oxidation state and the secondary valency to the coordination number of the metal.
  3. The primary valency is satisfied by only negative ions whereas the secondary valency either by anions or neutral molecules or both.
  4. The secondary valencies are directed in space towards fixed positions around the neutral atom.
Hence, options A, B and C are correct.

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

Which of the following is not true about the ionic solids?

  1. Bigger ions form the close packed structure.

  2. Smaller ions occupy either the tetrahedral or the octahedral voids depending upon their size.

  3. Occupation of all the voids is not necessary.

  4. The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In ionic solids anions (which are normally longer in size than cations forms closed pack array. 

The cation occupies one of the two types of holes remaining between the anions (either tetrahedral void or octahedral void). 
Depending on the relative sizes of cations and anions, the voids are filled. Occupation of voids depends on the stoichiometry of the compounds. It is not necessary that all voids get filled.

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

$KCl(s)$ is:

  1. An ionic substance

  2. A polar covalent substance

  3. A nonpolar covalent substance

  4. An amorphous substance

  5. A metallic network
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Potassium chloride KCl is a metal halide salt composed of potassium and chloride. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water and its solutions have a salt-like taste.


In aqueous solution,

$KCl\longrightarrow { K }^{ + }+{ Cl }^{ - }$

It is an ionic substance in solid state.

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

Which of the following ionic solids has the lowest melting point?

  1. $KCl$
  2. $NaCl$
  3. $LiF$
  4. $LiCl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Melting point of an ionic compound is determined by the electrostatic attraction between cations and anions. It takes a lot of energy to overcome this attraction to allow the ions to move freely and form a liquid. The factor witch effect melting point is charge of the ion. Since, $KCl$ has $+1$ and $-1$ charge on its' cations and anions respectively. Hence, it has the lowest melting point.


Hence, the correct option is $A$

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

Metallic bonding is explained by :

  1. band model

  2. electron-sea model

  3. both (a) and (b)

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

Both theories have their own arguments to explain metallic bonding.
Each metal atom allows its electrons to roam freely, so these atoms become positively charged cations. These cations are kind of like a positively charged island and are surrounded by a sea of negatively charged electrons.

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

Which of the following molecules has polar bonds but is a nonpolar molecule?

  1. $H _{2}$
  2. $H _{2}O$
  3. $NH _{3}$
  4. $NaCl$
  5. $CO _{2}$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Carbon dioxide $\displaystyle CO _2 $ has polar bonds but is a nonpolar molecule. The structure of $\displaystyle  CO _2$  is linear. The individual bond dipoles cancel each other as they point in opposite direction and are equal in magnitude. Hence, the molecule is non polar with zero dipole moment.