05.04.2016 Views

Modern Engineering Thermodynamics

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

H 2 O !ð1 − yÞH 2 O + yðv H2 ÞH 2 + yðv O2 ÞO 2<br />

(Continued )<br />

15.12 Chemical Equilibrium and Dissociation 633<br />

Degree of dissociation, y<br />

FIGURE 15.10<br />

Example 15.15, Solution, part a.<br />

1.0<br />

0.9<br />

0.8<br />

0.7<br />

0.6<br />

0.5<br />

0.4<br />

0.3<br />

0.2<br />

0.1<br />

CO 2 → (1 − y)CO 2 + (y)CO + (y/2)O 2<br />

p T = p 0 = 0.100 MPa<br />

0.0<br />

0 1000 2000 3000 4000 5000 6000<br />

Equilibrium temperature, T(K)<br />

0.8<br />

Degree of dissociation, y<br />

FIGURE 15.11<br />

Example 15.15, Solution, part b.<br />

0.7<br />

0.6<br />

0.5<br />

0.4<br />

0.3<br />

0.2<br />

0.1<br />

0.0<br />

0.1<br />

CO 2 → (1 − y)CO 2 + (y)CO + (y/2)O 2<br />

1.0<br />

10.0<br />

Total mixture pressure, pm (MPa)<br />

p 0 = 0.100 MPa<br />

T = 3000. K<br />

100.0<br />

Exercises<br />

43. Use the solution given in Example 15.15 to determine the dissociation equation for CO 2 at 3000. K and 5.000 MPa.<br />

Answer: CO 2 → 0.8472(CO 2 ) + 0.1528(CO) + 0.0764(O 2 ).<br />

44. Use the solution given in Example 15.15 to determine the dissociation equation for CO 2 at 3000. K and 0.01000 MPa.<br />

Answer: CO 2 → 0.3194(CO 2 ) + 0.6806(CO) + 0.3403(O 2 ).<br />

45. Use the solution given in Example 15.15 to determine the total mixture pressure that produces the following<br />

dissociation reaction for CO 2 at 3000 K: CO 2 → 0.50(CO 2 ) + 0.50(CO) + 0.25(O 2 ). Answer: p m = 0.94 Pa.<br />

An equivalent and perhaps more straightforward way of approaching a dissociation equilibrium reaction is illustrated<br />

in the next example.<br />

EXAMPLE 15.16<br />

Determine the amount of H 2 produced as a function of temperature in the thermal dissociation of water vapor at the SRS<br />

pressure (i.e., p m = p°).<br />

Solution<br />

The overall irreversible dissociation reaction equation for water vapor is

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!