26.07.2021 Views

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

<strong>and</strong> the system will once again be at equilibrium. Changes in the partial pressures of the various<br />

substances in the reaction mixture (Equation 15.34) as a function of time are shown in Figure 15.11 "The<br />

Partial Pressures of H".<br />

Figure 15.11 The Partial Pressures of H2, N2, <strong>and</strong> NH3 as a Function of Time Following the Addition<br />

of More H2 to an Equilibrium Mixture<br />

Some of the added hydrogen is consumed by<br />

reacting with nitrogen to produce more ammonia, allowing the system to reach a new equilibrium<br />

composition.<br />

We can force a reaction to go essentially to completion, regardless of the magnitude ofK, by continually<br />

removing one of the products from the reaction mixture. Consider, for example,<br />

the methanation reaction, in which hydrogen reacts with carbon monoxide to form methane <strong>and</strong> water:<br />

Equation 15.35<br />

CO g<br />

( ) + 3H2( g) CH 4( g) + H2O( g)<br />

This reaction is used for the industrial production of methane, whereas the reverse reaction is used for the<br />

production of H2 (Example 14). The expression for Q has the following form:<br />

Equation 15.36<br />

Q = [CH 4][H2O] [ CO][H2]3<br />

Regardless of the magnitude of K, if either H2O or CH4 can be removed from the reaction mixture so that<br />

[H2O] or [CH4] is approximately zero, then Q ≈ 0. In other words, when product is removed, the system is<br />

stressed (Q

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

Saved successfully!

Ooh no, something went wrong!