Question

The thermal decomposition of dimethyl ether CH 3 2 O g CH 4 g H 2 g CO g is to be carried out in an isothermal 2.00-liter laboratory reactor at 600°C. The reactor is charged with pure dimethyl ether at a pressure of 350 torr. After about two hours, the reactor pressure is 875 torr. (a) Has the reaction proceeded to completion at the end of the two-hour period? If not, what percentage of the dimethyl ether has decomposed? (b) Taking elemental species [C(s), H2(g), O2(g)] at 25°C as references, prepare and fill in an inlet-outlet enthalpy table. (See Example 9.5-2.) Use tabulated data for methane, hydrogen, and carbon monoxide, and the following data for dimethyl ether: Δ H f 180.16 kJ mol C p J mol K 26.86 0.1659 T 4.179 10 5 T 2 T in kelvins (c) Calculate Δ H r 600 C and Δ U r 600 C for the dimethyl ether decomposition reaction. (d) How much heat (kJ) was transferred to or from the reactor (state which it is) during the two-hour period of the reaction? (e) Suppose the reaction were instead carried out in an expandable reactor at 600°C at a constant pressure of 350 torr, with the same final percentage decomposition of dimethyl ether. Calculate the final volume of the reactor and the required amount of heat transfer. (Note: These should both be quick calculations.) Explain why the values of Q calculated in Part d and in this part are different, even though the initial conditions and extents of reaction are the same.

Answer 1