Fourth Chapter Solved Exercise MCQs Of FSc First Year Chemistry

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Fourth chapter liquids and solids solved Exercise MCQs with explanation

1: London dispersion forces are the only forces present among the?

a) Molecules of water in liquid

b) Atoms of helium in gaseous state at high temperature

c) Molecules of solid iodine

d) Molecules of hydrogen chloride gas

Explanation

London forces are more prominent among non-polar molecules like I2, which is a member of VII-A group. All the halogens are non-polar diatomic molecules. So, these forces are more prominent among them. Among all halogens, the polarity of I2 is maximum. So, option (c) is correct.

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2: Acetone and Chloroform are soluble in each other due to:

a) Intermolecular hydrogen bonding

b) dipole- dipole interaction

c) Instantaneous dipoles

d) All of the above

Explanation

In chloroform, three chlorine atoms are present. These atoms deprive the carbon atoms of the electrons. Due to inductive effect, the C-H bond also becomes polar. The H- atom develops sufficient polar positive charge. Thus, partial positive charged hydrogen atom can form a strong H-bond with oxygen atom of acetone. So, option (a) is correct.

3: NH3 shows a maximum boiling point among the hydrides of V-A group elements due to:

a) Very small size of nitrogen

b) Lone pair of electrons present on nitrogen

c) Enhanced electronegative character of nitrogen

d) Pyramidal structure of NH3

Explanation

In group V-A of the periodic table, nitrogen is highly electronegative. It develops sufficient partial negative charge. This causes strong H- bonding.

In NH3, lone pairs are present in H3, AsH3, SbH3 and BiH3 as well. So, option (c) is correct.

4: When water freezes at 0oC, its density decreases due to?

 a) Cubic structure of ice

b) Empty spaces present in the structure of ice

c) Change of bond lengths

d) Change of bond angles

Explanation

There are empty spaces present in the structure of the ice. The molecule of water is bent when hydrogen bonds are fixed at their positions. Thus, vacant places are left behind. That is why, when water freezes at 0oC, it occupies 9 percent more space and its density is decreased .So, option (b) is correct.

5: In order to maintain the boiling point of water at 110oC, the external pressure should be:

a) Between 760 torr and 1200 torr

b) Between 200 torr and 760 torr

c) 760 torr

d) Any value of pressure

Explanation

The normal boiling point of water is 100oC at 760 torr. To boil at 110oC, high pressure between 760 and 120 torr may be applied. So, option (a) is corrects

6: Ionic solids are characterized by:

a) Low melting points

b) Good conductivity in solid state

c) High vapor pressure

d) Solubility in polar solvents.

Explanation

 Ionic solids are polar in nature. According to the principle, “like dissolves the like”, polar substances are soluble in polar solvents. Hence, option (d) is correct.

7: Amorphous solids:

  1. Have sharp melting points.
  2. Undergo clean cleavage when cut with knife.
  3. Have perfect arrangement of atoms.
  4. Can possess small regions of orderly arrangement of atoms.

Explanation

The solids in which the atoms, ions or molecules have irregular arrangement are called amorphous solids. A long range regularity does not exist in between them but they possess small degree of orderly arrangement. So, option (d) is correct.

8: the molecules of CO2 in dry ice form the:

  1. Ionic crystals
  2. Covalent crystals
  3. Molecular crystals
  4. Any type of crystal

Explanation

The molecules of CO2 in dry ice are non-polar. The solid forming non-polar molecules are called as molecular crystals. So, answer (c) is correct.

9: which of the following is a pseudo solid?

  1. CaF2
  2. Glass
  3. NaCl
  4. All

Explanation

A pseudo solid can be regarded as super cooled liquid. Among these only glass is regarded as such a solid. So, option (b) is correct.

10: Diamond is a bad conductor because:

  1. It has a tight structure.
  2. It has a high density.
  3. There are no free electrons present in the crystal of diamond to conduct electricity.
  4. None of the above.

Explanation

Diamond is one of the best example of covalent solids and all the covalent solids are bad conductor of electricity due to the absence of the free electrons and ions. So, option (c) is correct.