Class 11th

This is a short answer type question as classified in NCERT Exemplar

The increase in temperature increases the kinetic energy of the molecules which decreases the intermolecular forces operating between its particles and hence, the viscosity of a liquid decreases. So, the viscosity of a liquid  decreases if its temperature is increased.

This is a short answer type question as classified in NCERT Exemplar

Hexane is a  nonpolar molecule which has london force between the molecules, which is a weak force. 

Water and glycerine have  O atoms which is an electronegative atom that forms H bonding between the molecules along with dipole-dipole interaction. 

Glycerine has three  O atoms, so it forms more H bonding and hence, has stronger  intermolecular forces.

So the increasing order of intermolecular forces is Hexane   <   Water  <  Glycerin. Stronger the  intermolecular forces, the greater is the viscosity, so the increasing order of their viscosities is: 

Hexane   <   Water  <  Glycerin

This is a short answer type question as classified in NCERT Exemplar

The two phenomena that can be explained on the basis of surface tension are:

1. Spherical shape of rain droplets.

2. Capillary action due to which the liquid in capillary rises and falls.

This is a short answer type question as classified in NCERT Exemplar

Unit of 'P'  =  N m^-2

Unit of 'a'   =  N m^-2  X   (m³)²  / (mol)²

= N-m⁴ mol^-2

Unit of 'a' when pressure is in atm, and volume in dm³   

Unit  of 'P' =  atm

Unit of 'a'   =  atm  X  (dm³)²  / (mol)²

= atm-dm⁶ mol^-2

This is a short answer type question as classified in NCERT Exemplar

The CO₂ gas cannot be liquified at the 32°C and 80 atm pressure as the given temperature and pressure are above critical temperature (T_c) and critical pressure (p_c) which are 30.98°C and 73 atm respectively.

This is a short answer type question as classified in NCERT Exemplar

(i) The value of Z for an ideal gas is 1. 

(ii) For real gas, the value of Z > 1 above Boyle's temperature 

This is a short answer type question as classified in NCERT Exemplar

The assumption of kinetic theory of gases that there is no force of attraction between the molecules of a gas is applicable for real gases. The evidence for this is  that the real gas can be liquified at high pressure and low temperature. This proves that there is force of attraction between the molecules of gas.

This is a short answer type question as classified in NCERT Exemplar

The two intermolecular forces that exist between HF molecules in liquid state are hydrogen bonding (as F is a highly electronegative atom) and  dipole-dipole interaction (as HF is a polar molecule).

This is a short answer type question as classified in NCERT Exemplar

The energy which arises due to motion of atoms or molecules in a body is known as thermal energy and the average kinetic energies of all the molecules increases with increases in temperature.