[scottshannon]

The compound propionic acid decomposes at elevated temperatures to give methyl ketene and water.

C2H5COOH(g) ---------> CH3CH=C=O(g) + H2O(g)

The total pressure of the reaction mixture changes with time, as shown by the following data at 507°C:

Time (s)           Ptot (atm)                      PC2H5COOH (atm)
0                           .5180                              .5180

14.2                       .7122                                ?

28.4                        .8004                               ?

42.6                        .8509                               ?

56.8                        .8836                               ?


A) Calculate the partial pressure of C2H5COOH at each time from these data, and enter the values in the table above. Assume that at time 0, C2H5COOH is the only gas present.

B) Are the data better described by a first-order or a second-order rate expression with respect to C2H5COOH concentration? first or second

[DWH]

More of a math problem than a chemistry problem (as are most kinetic problems).
Remember that partial pressure depends on moles of gas, not on its identity.

Every thing is a gas.  So, you'll lose moles of reactant as you gain moles of product.
Set up an algebra equation.  I'll give you the first answer to check yourself - you can do the rest.

At 14.2s you'd have 0.3238atm