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Previous Year Questions of Chemical Bonding

Previous Year Questions of Chemical Bonding

Q 2714312259

The valency of an element depends upon the
NDA Paper 2 2017
(A)

total number of protons irian atom

(B)

mass number of an atom

(C)

total number of neutrons in an atom

(D)

total number of electrons in the. outer Most shell of an atom

Solution:

Correct Answer is `=>` (D) total number of electrons in the. outer Most shell of an atom
Q 2900723618

Which one of the following statements is correct?
NDA Paper 2 2016
(A)

Covalent bonds are directional

(B)

Ionic bonds are directional

(C)

Both covalent and ionic bonds are directional

(D)

Both covalent and ionic bonds are non-directional

Solution:

Correct Answer is `=>` (A) Covalent bonds are directional
Q 1628656501

Which one among the following does not wet the walls of the glass vessel in which it is kept?
NDA Paper 2 2015
(A)

Water

(B)

Alcohol

(C)

Mercury

(D)

Phenol

Solution:

Mercury exhibits more cohesion than adhesion with glass so it does not wet the walls of the glass vessel, if kept in it.
Correct Answer is `=>` (C) Mercury
Q 1770712616

Which of the following element combinations will form ionic compounds?

1. Ca (Z = 20) and Ti (Z = 22)
2. Si (Z = 14) and Br (Z = 35)
3. Mg (Z = 12) and Cl (Z = 17)

Select the correct answer using the codes given below
NDA Paper 2 2014
(A)

Only 2

(B)

Only 3

(C)

2 and 3

(D)

1, 2 and 3

Solution:

An ionic bond is formed when one of the atoms can donate electron to achieve the inert gas electron configuration, and the other atom needs electrons to achieve the inert gas electron configuration. Ionic bond is formed between metals and non-metals.
Correct Answer is `=>` (B) Only 3
Q 1780623517

The very high heat of vaporisation of water is mainly a result of
NDA Paper 2 2014
(A)

van der Waals forces

(B)

covalent bonds

(C)

interionic attraction

(D)

hydrogen bonding

Solution:

The very high heat of vaporisation of water is

mainly a result of hydrogen bonding.
Correct Answer is `=>` (D) hydrogen bonding
Q 1712167030

The number of valence electrons in the `O^(2-)` ion is
NDA Paper 2 2014
(A)

`4`

(B)

`6`

(C)

`8`

(D)

`10`

Solution:

The very high heat of vaporisation of water is

mainly a result of hydrogen bonding.
Correct Answer is `=>` (D) `10`
Q 2317845780

The bond which is present between water molecules is



NDA Paper 2 2013
(A)

electrovalent bond

(B)

covalent bond

(C)

hydrogen bond

(D)

van der Waals' bond

Solution:

A hydrogen bond is the electromagnetic attractive interaction between polar molecules, in which hydrogen (H) is bond to highly electronegative atom, such as nitrogen (N), oxygen (O) or fluorine (F).
In water, the negative part is the oxygen atom in `H_2O`. Hydrogen bonds in liquid water are short lived, but the H-bonds in solid water (ice) are quite stable.
Correct Answer is `=>` (C) hydrogen bond
Q 2980723617

The bond which is present between water molecules is
NDA Paper 2 2012
(A)

electrovalent bond

(B)

covalent bond

(C)

hydrogen bond

(D)

van der Waals' bond

Solution:

A hydrogen bond is the electromagnetic attractive interaction between polar molecules, in which hydrogen (H) is bond to highly electronegative atom, such as nitrogen (N), oxygen (O) or fluorine (F).
In water, the negative part is the oxygen atom in `H_2O`. Hydrogen bonds in liquid water are short lived, but the H-bonds in solid water (ice) are quite stable.
Correct Answer is `=>` (C) hydrogen bond
Q 2327456381

Three elements Na, S and O combine to form a compound `Na_2SO_3`. What is the valency of S in this compound?
NDA Paper 2 2012
(A)

2+

(B)

4+

(C)

6+

(D)

8+

Solution:

Sodium sulphite is a soluble sodiurn salt of sulphurous acid with the chemical formula `Na_2SO_3`. It is a product of sulphur dioxide scrubbing, a part of the flue-gas desufphurisation process. It is also used as a preservative to prevent dried fruit from discoloring, and for preserving meats, and is used in the same way as sodium thiosulphate ta convert elemental halogens to their respective hydrohalic acids, in photography and for reducing chlorine levels in pools. The valency of S in the compound `Na_2SO_3` is 8+.
Correct Answer is `=>` (D) 8+
Q 2357867784

All the elements in a group (family) have a common valency. e. g., all the elements of the carbon family (carbon, silicon, germanium, tin and lead) have common valency four. However, some of these elements can also have valency two. Which of the following can have valency two?
NDA Paper 2 2011
(A)

Silicon, germanium and tin

(B)

Germanium and tin

(C)

Germanium, tin and lead

(D)

Tin and lead

Solution:

The elements of the carbon family show tetra valency
hence they have oxidation state of +4. In addition germanium, tin
and lead can also have valency two and hence they also show
+2 oxidation state. On going down the group +2 oxidation state
becomes more stable `Ge^(2+) < Sn^(2+) < Pb^(2+)`.
Correct Answer is `=>` (C) Germanium, tin and lead
Q 2348412303

As compared to covalent compounds, electrovalent compounds, generally have
NDA Paper 2 2010
(A)

low melting point and low boiling point

(B)

low melting point and high boiling point

(C)

high melting point and low boiling point

(D)

high melting point and high boiling point

Solution:

As compared to covalent compounds, electrovalent compounds have high melting and boiling points. It is due to strong forces of attraction between the ions in the crystal of an electrovalent compound. Hence, a large amount of energy is required to over come these forces and breakdown the crystal lattice.
Correct Answer is `=>` (D) high melting point and high boiling point
Q 2347067883

Which of the following salts are insoluble in water?
NDA Paper 2 2008
(A)

Chlorides of Fe and Mn

(B)

Nitrates of Ag and Pb

(C)

Carbonates of Pb and Cu

(D)

Phosphates of Na and `NH_4`

Solution:

The salts of carbonates of `Pb` and `Cu` are insoluble in water.
Correct Answer is `=>` (C) Carbonates of Pb and Cu
Q 2327378281

Analysis shows that a binary compound of X (atomic mass `= 1 0`) and Y (atomic mass `= 20`) contains `50%` X. What is the formula of the compound?
NDA Paper 2 2007
(A)

`XY`

(B)

`X_2Y`

(C)

`XY_2`

(D)

`X_2Y_3`

Solution:

Hence, the formula is `X_2Y_2`
Correct Answer is `=>` (C) `XY_2`
Q 2357680584

An element A has valencies equal to 3 and 5. It combines with another element B having valency equal to 2. What are formula of the compounds thus formed'?
NDA Paper 2 2007
(A)

`A _5B_ 3` and `A _2 B_5`,

(B)

`A_ 3 B_ 2` and `A_ 5 B_ 2`

(C)

`A _2 B_ 3` and `A _2 B_ 5`

(D)

`A _2 B_ 3` and `A_ 3 B_ 5`

Solution:

Element A has valencies `= 3` and `5`

and element B has valency `= 2`

`:.` Formulae of the compounds will be `A_2B_3` and `A_2B_5` .
Correct Answer is `=>` (C) `A _2 B_ 3` and `A _2 B_ 5`
Q 2317080880

The octet rule is not valid for which one of the following molecules'?
NDA Paper 2 2007
(A)

`CO_2`

(B)

`H_2S`

(C)

`NH_3`

(D)

`BF_3`

Solution:

Octet rule is not valid for `BF_3`, because in `BF_3`, octet of `B`
is not complete.

Octet incomplete `(underset ( : underset(..)overset(..)F : ) overset ( : underset(..)overset(..)F : )( : underset(..)overset(..)B :` `: underset(..)overset(..)F : )` octet complete
Correct Answer is `=>` (D) `BF_3`
 
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