09-214 Physical Chemistry Name_ANSWER KEY (20 pts total)_

Quiz 1 January 24, 2001

Closed book. No equations in calculators. Show all work.

Some thermodynamics discussed so far is true in general, some is true only under restricted conditions. For each of the following, state what are the minimum conditions to make them true. (Some subscripts normally present may have been omitted. You may assume that the system is uniform in properties: T, P, E, and so on are everywhere the same.)

(a) E = q + w

(First Law...no conditions) (3 pts)

(b) q =H

(P = constant)(3 pts)

(c)H =E + n(PV)

Ideal gas, number of moles is constant(2+1=3 pts)

(d) E = 3RT/2

Ideal, monatomic gas, one mole(the 'delta' is a typo and shouldn't really be there but is otherwise harmless).(1+1+1=3 pts)

What does adiabatic mean?

q = 0 (thermally insulated system, no heat transferred)(3 pts)

One mole of a certain real gas obeys the equation of state . "a" is a constant, characteristic of the gas. What is the expression for the reversible work of expansion of such a gas going isothermally from V₁ to V₂?

w=-PdV(1 pt); PV+(a/V)=RT; P=(RT/V)-(a/V²)=P_ext for reversible expansion;w=-RT(dV/V)+a(dV/V²)(2 pts)=-RTln(V₂/V₁)-a[(1/V₂)-(1/V₁)](1+1=2 pts)