Suppose we want to increase the entering total pressure. How does the pressure drop parameter, , vary with the entering to total pressure, P_o? [see Preface Table P1, Q5 -- Question that probes implications and consequences. I.e., what would be the consequence of changing the inlet pressure, P_o?]

a)   a increases with increasing P_o.

b)   a decreases with increasing P_o.

c)   a does not change with P_o.

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Solution

a decreases with increasing P_o

We note that increasing the total pressure increases the concentration

for a fixed y_ao. For Pure A, y_ao=1.0.  Therefore, the rate of reaction (A --> B) would increase.

we note we have competing effects

1)   Increasing P_o increases the rate initially

2)   Increasing P_o increases the rate at which y decreases and therefore the rate decreases

      To determine which of the above effects will dominate and cause the conversion to increase or decrease will depend on a number of things such as reaction order, value of a, and other parameter values. Consequently, we would need to run the simulation. However, you will find that as P_o increases, so will X, as a loose "rule of thumb".