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Else_AIEC-INGLE_cH003.qxd 7/13/2006 1:45 PM Page 91
3.3 T w Reactors o-Phase Agitated 91

Then

1 x 2 SO
C SO 2 C , SOi 2
1 0.015 x SO 2
C O2,i C SOi 2, x x SO 2
C 0.5
O2
1 0.015 x 1 0.015 x
2 SO SO 2
Example 3
Consider the gas-phase reaction
2A B 2 C
which is carried out isothermally and isobaricallyThe reaction rate is first order in . A and
first order in B. The feed concentration of A and B is 0.5 mol/L. Express the rate of reac-
tion – r A v ersion, solely as a function of con ealuating all possible parameters in v ed. v olv

Solution
First of all, we hae to determine which the limiting reactant is. The way to determine
v
which reactant is limiting is to divide the moles of each reactant by the coeficient from f
the balanced equation associated with that reactant. The smallest number that comes out
indicates which reactant is the limiting one. This reactant limits how much of e ery other v
A,
species made or needed for the reaction. F this calculation gies 0.25 and for B, 0.5. v
or
Thus, A is the limiting reactant and the calculation of , and x should based on it.
,
R
The parameter is

1
cd a b 20 1
2

a 2 2
actor The expansion f is
R
N A,i 0.5  1 
  0.25
R
N tot,i 1  2 
The moles of A and B after a con v el of v ersion le A equal to x are
N N x (1 )
A A,i
x
N B N B,i N A,i
2
The concentrations of A and B are
N A 1 x A 1 x A
C A C A,i 0.5
V (1 R x ) A 1 R x A 1 0.25 x A
i
N B C B,i C A,i x A 1 0.5 x A
C B 0.5
V (1 xx R A ) 1 R x A 2(1 ) R x A 1 0.25 x A
i