Constant volume versus constant pressure batch reactor

missmaria

1. The problem statement, all variables and given/known data
Consider the following two well-mixed, isothermal batch reactors for the elementary and irreversible decomposition of A to B, A[tex]\stackrel{k}{\rightarrow}[/tex]2B
reactor1: The reactor volume is constant (Pressure is variable)
reactor2: The reactor pressure is constant (Volume is variable)
Both reactors are charged with pure A at 1.0 atm and k=0.35min-1
a) what is the fractional decrease in the concentration of A in reactors 1 and 2 after 5 minutes?
b)what is the total molar conversion of A in reactors 1 and 2 after 5 minutes?


2. Relevant equations
I'm not sure


3. The attempt at a solution
Ok, so part a for a constant volume reactor was simple, since rA=-kC[tex]_{A}[/tex], then the rate of change in concentration of A turned out to be ln(C[tex]_{A}[/tex]/C[tex]_{A0}[/tex])=-kt
but variable volume has me stumped. I figured out that -k=[tex]\frac{dC_{A}}{dt}[/tex]+[tex]\frac{1}{V}[/tex][tex]\frac{dV}{dt}[/tex] but i don't know where to go from here.

I don't even know where to start for part b, please help...