Daily Practice Problems

Overall

Score Total no of Correct Incorrect Unattempted

question
0 10 1 4 5

Solution
1 The correct order of melting point of alkali metal  12 s
chlorides is:
A N aCl > KCl > CsCl

B N aCl > CsCl > KCl

C CsCl > KCl > N aCl

D CsCl > N aCl > KCl

Solution : A

4 mins

Melting point depends on lattice energy. Greater

the lattice energy, greater is the melting point.
Lattice energy depends on the size of the ions
involved. Smaller the internuclear distance, larger
the lattice energy.

Hence, the correct order is: N aCl > KCl > CsCl


2 An element A has a valence electronic  26 s
configuration 3s 2
3p
5
and the other element B has a
valence electronic configuration 3s . The bond
1

formed between them is:

A Covalent
B Ionic
C Coordinate covalent
D Cannot predict

Solution : B

3 mins

From the valence electronic configuration, the

element A is Cl and the element B is N a. N a is a
metal and Cl is a non metal. The bond formed
between them will be ionic.
N a loses one electron to attain a noble gas

configuration (N e) and forms N a +

Cl gains one electron to attain a noble gas

configuration (Ar) and forms Cl . −

They form N aCl which is an ionic compound.

-1.0/4.0 
3 If N a is larger than M g
+ 2+
ion and S 2−
ion is larger  12 s
than Cl ion, which of the following will be the
−

least soluble in water?

A N aCl

B N a2 S

C M gCl2

D M gS

Solution : D

3 mins

Solubity of a compound in water depends on two

factors. They are:
1. lattice energy
2. hydration energy.

When the hydration energy is more than the

lattice energy the compound becomes soluble in
water.

Lattice energy is directly proportional to the

product of the charges on the cation and the
anion and inversely proportional to the distance
between the charges.

M gS has M g and S . The product of charges

2+ 2−

is the highest and so will be the lattice energy.

Hence, M gS is the least soluble.


4 Predict the correct order of mobility of Be , M g
2+ 2+
,
2s
Sr
2+
and Ca ions in aqueous medium.
2+

A Be
2+
>M g 2+
> Ca > Sr
2+ 2+

B Be
2+
< Mg 2+
< Ca < Sr
2+ 2+

C Be
2+
> Mg 2+
>Sr > Ca
2+ 2+

D Mg
2+
< Be < Sr < Ca
2+ 2+ 2+

Solution : B

6 mins

Ionic mobility depends on the hydration of the ion

in aqueous medium.

Smaller the size of the cation (high charge

density), more the degree of hydration (more it is
surrounded by water molecules), higher will be
the hydrated radii and hence least will be
mobility.

The order of the size for the given ions is Be < 2+

Mg < Ca < Sr
2+ 2+ 2+

∴ The order of ionic mobility will be

Be <M g < Ca < Sr

2+ 2+ 2+ 2+


5 Which of the following is arranged in the increasing  1 m 11
order of hydration energy? s

A Cu
2+
< Fe
3+
< Fe
2+
< Al
3+

B Fe
2+
< Cu
2+
< Fe
3+
< Al 3+

C Al
3+
< Fe
3+
< Fe
2+
< Cu
2+

D Fe
3+
< Al
3+
< Cu
2+
< Fe
2+

Solution : B

4 mins

Hydration energy is the amount of energy

released upon solvation of the ion in water.

Hydration energy depends on the charge on the

ion and the ionic radius. Higher the charge,
smaller the size, greater is the hydration energy.
Considering both the charge and the size,
hydration energy will follow the order
2+ 2+ 3+ 3+
Fe < Cu < Fe < Al

and the ioinic size order is

2+ 2+ 3+ 3+
Fe > Cu > Fe > Al


6 Which of the following compounds has the  21 s
minimum cation to anion size ratio?
A CsF

B LiI

C LiF

D CsI

Solution : B

1 mins

The given anions are F −

and I and the size (R)
−

order is R < R
F I

The given cations are Li and Cs and the size

+ +

(R) order is R < R

Li Cs

For the cation to anion ratio to be minimum, the

compound must have a large anion and a small
cation. Here, I is the largest anion and Li is the
− +

smallest cation.
Therefore, LiI has the minimum cation to anion
size ratio.

-1.0/4.0 
7 The hydration energy of:  46 s

A Be
2+
> Na
+

B Be
2+
< Na
+

C Be
2+
= Na
+

D None of the above

Solution : A

1 mins

Hydration energy is directly proportional to the

charge on the ion and inversly proportional to the
size of the ion. As the size of N a is greater than
+

Be
2+
and the charge on beryllium ion (+2) is
greater than the charge on sodium ion (+1), the
hydration energy of Be is greater than that of
2+

Na .
+

-1.0/4.0 
8 The lattice energy order for lithium halides is:  20 s

A LiF > LiCl > LiBr > LiI

B LiCl > LiF > LiBr > LiI

C LiBr > LiCl > LiF > LiI

D LiI > LiBr > LiCl > LiF

Solution : A

1 mins

We know that the lattice energy is directly

proportional to the product of the charges of the
ions and inversely proportional to the separation
between the centres of the ions, i.e., the size of
the ions.
Since all the compounds have the same cation,
i.e., Li , the size of the anions will be considered.
+

Down the group, size increases, i.e.,

− − − −
F < Cl < Br < I

Thus, the correct order of lattice energy is:

LiF > LiCl > LiBr > LiI


9 Which one of the following alkali metal chlorides  21 s
has the highest melting point?
A KCl

B RbCl

C CsCl

D N aCl

Solution : D

2 mins

Since all the compounds have the same anion,

i.e., Cl , the size of cations will be considered.
−

Melting point depends upon the lattice energy.

Greater the lattice energy, greater is the melting
point. Smaller the size of the ions, greater the
lattice energy.
Down the group, size increases, i.e.,
+ + + +
Na < K < Rb < Cs

Hence, among all N aCl has the highest melting

point as it has the highest lattice energy.

-1.0/4.0 
10 Which of the following factors affects the hydration 6s
energy of an ion?
A Hydration energy depends on charge of the ion
B Hydration energy depends on the ionic radii
C Hydration energy depends on the mass of the
ion
D Both A and B

Solution : D

1 mins

Hydration energy of an ion is directly proportional

to the charge of the ion and inversly proportional
to its ionic radii.
Thus, higher the charge to size ratio i.e charge
density, higher will be the hydration energy.

4.0/4.0 