CY11001 (Physical Chemistry) Tutorial 2

Assume ideal behaviour unless stated otherwise.

1. Suggest the pressure and temperature at which 1.0 mol of NH3 will be in a state that

corresponds to 1.0 mol H2 at 1.0 atm and 25C. The critical pressure and temperature are 12.8 atm, 33.23 K (for H2) and 111.3 atm, 405.5 K (for NH3).

2. A scientist proposed the following equation of state: p= RT/Vm - B/Vm2 + C/Vm

3. Show that the equation leads to ideal behaviour. Find the critical constants of the gas in terms of B and C and an expression for the critical compression factor.

3. A sample consisting of 1 mol Ar is expanded isothermally at 0 C from 22.4 dm3 to 44.8

dm3 (a) reversibly, (b) against a constant external pressure equal to the final pressure of

the gas, and (c) freely (against zero external pressure). For the three processes

calculate q, w, U, and H.

4. When 229 J of energy is supplied as heat to 3.0 mol Ar(g) at 1 atm, the temperature of

the sample increases by 2.55 K. Calculate the molar heat capacities at constant volume

and constant pressure of the gas.

5. A sample of 4.0 mol O2 is originally confined in 20 dm3 at 270 K and then undergoes

adiabatic expansion against a constant pressure of 600 Torr until the volume has

increased by a factor of 3.0. Calculate q, w, T, U, and H. Cp,m=29.355 J K-1 mol-1 for

O2. (The final pressure of the gas is not necessarily 600 Torr.)

6. For each of the following processes, deduce whether the quantities q, w, U, and H are

positive, negative or zero (a) Reversible melting of ice at 1 atm and 00 C (b) Reversible

adiabatic expansion of a perfect gas (c) Adiabatic expansion of a perfect gas into a

vacuum (Joule experiment) (d) Reversible heating of a perfect gas at a constant

pressure.

7. The isothermal compressibility of copper at 293 K is 7.35x10-7 atm-1. Calculate the

change in pressure that must be applied in order to increase its density by 0.08 %.

8. Given that 0.25 K atm-1 for nitrogen, calculate the value of its isothermal Joule

Thomson coefficient. Calculate the energy that must be supplied as heat to maintain

constant temperature when 15.0 mol N2 flows through a throttle in an isothermal Joule

Thomson experiment and the pressure drop is 75 atm. Cp,m= 29.125 JK-1mol-1.