CHM 2045C Module 6 Sample Exam

Module 6 Sample Answers

Module Six Part B: Discussion Question 5 points

In the Real Gas Equation: (P + an²/V²) (V - nb) = n RT a pressure correction factor was added. Why? (What assumptions of the kinetic theory breakdown under extreme conditions of temperature and pressure?)

In Section 12.9 on page 576 the answer is in the third paragraph!

Another assumption of the kinetic molecular theory is that collisions between the molecules are elastic-that is, that the atoms or molecules of the gas never stick to one another by some type of intermolecular force. This is no true at extreme conditions of overcrowding. When a molecule is about to strike the wall of its container, other molecules in the vicinity exert a slight attraction for the molecule and pull it away from the wall. As a result of the intermolecular forces, molecules strike the wall with less force than they would in the absence of intermolecular attractive forces. Therefore, in a real gas, the observed pressure is less than the predicted pressure by the ideal gas law and a pressure correction factor is added to account for this pressure loss.

Also a volume correction factor was subtracted. Why? (What assumptions of the KMT breakdown under extreme conditions?)

In Section 12.9 on page 576 the answer is in the second paragraph!

The kinetic molecular theory and the ideal gas law are concerned with the volume available to the molecules to move about, not the volume of the molecules themselves. It is clear the volume occupied by the gas molecules is NOT negligible at high pressures (or extreme low temperatures. The available volume is less than the volume of the container. The volume the molecules occupy must be subtracted from the volume of the container to obtain the volume of free space the molecule can move.

Module Six-Part C Standard Conditions/Molar Volume 5 points

State standard conditions (STP) in three units of pressure (the last is your choice) and ^oC and K temperatures:

_760__mmHg or _760__torre= __1___atm = Bonus: _29.9 in_ = _14.7 psi_= 101 kPa

__0_ ^oC = _273__K

Are the values for the Molar Gas Volume Constant:

1 mole _CO2 =__22.4__L _CO2@STP 1 mole _H2 =__22.4___L _H2@STP

1 mole _N2 =__22.4___L _N2@STP 1 mole _O2 =__22.4___L _O2@STP