# Homework Help: Constant volume versus constant pressure batch reactor

1. Oct 1, 2008

### 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$$\stackrel{k}{\rightarrow}$$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$$_{A}$$, then the rate of change in concentration of A turned out to be ln(C$$_{A}$$/C$$_{A0}$$)=-kt
but variable volume has me stumped. I figured out that -k=$$\frac{dC_{A}}{dt}$$+$$\frac{1}{V}$$$$\frac{dV}{dt}$$ but i don't know where to go from here.

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