An ammonia (NH3) molecule consists of 4 atoms at the corners of a distorted
tetrahedron as shown in the figure where the large blue ball is the N atom.
The molecules can translate and rotate but not vibrate.
(a) How many degrees of freedom are associated with this molecule?
(b) What is the molar heat capacity of a gas of these molecules at constant
volume according to the principle of equipartition of energy? What is the molar heat capacity
at constant pressure calculated from this?
(c) How much heat do two moles of the gas need to absorb at constant pressure in order to
increase the temperature of the gas from 250 K to 350 K?
(d) According to http://en.wikipedia.org/wiki/Ammonia_(data_page)#Thermodynamic_properties
the heat capacity at constant pressure of ammonia gas varies with temperature as shown in the
figure. How does the experimental value at room temperature (20 °C) compare with the value
estimated in part (b)? What is the origin of the discrepancy? Related to the last question is
why does the experimental heat capacity in the figure increase with increasing temperature?
tetrahedron as shown in the figure where the large blue ball is the N atom.
The molecules can translate and rotate but not vibrate.
(a) How many degrees of freedom are associated with this molecule?
(b) What is the molar heat capacity of a gas of these molecules at constant
volume according to the principle of equipartition of energy? What is the molar heat capacity
at constant pressure calculated from this?
(c) How much heat do two moles of the gas need to absorb at constant pressure in order to
increase the temperature of the gas from 250 K to 350 K?
(d) According to http://en.wikipedia.org/wiki/Ammonia_(data_page)#Thermodynamic_properties
the heat capacity at constant pressure of ammonia gas varies with temperature as shown in the
figure. How does the experimental value at room temperature (20 °C) compare with the value
estimated in part (b)? What is the origin of the discrepancy? Related to the last question is
why does the experimental heat capacity in the figure increase with increasing temperature?