Le Châtlier's Principle

Le Châtelier's Principle

  • Le Châtelier (1850-1936)

  • When a system at equilibrium is subjected to a stress (change in concentration, temperature, or pressure), the system will shift in a way to relieve the stress.

Haber-Bosch Process

^{-2}</p><ul><li><p>Reactionfavorsreactants.</p></li><li><p>Changeinconcentrationcanleadtofavoringproducts.</p></li></ul><h4id="8ad09a03−98e9−42a7−8a8c−335227ca0e0f"data−toc−id="8ad09a03−98e9−42a7−8a8c−335227ca0e0f"collapsed="false"seolevelmigrated="true">PressureandVolumes</h4><ul><li><p>Shiftstheequilibriumtowardsproducts(shiftingright).</p></li></ul><h4id="8c272fb3−3b86−46e4−a0b2−f4642918bef8"data−toc−id="8c272fb3−3b86−46e4−a0b2−f4642918bef8"collapsed="false"seolevelmigrated="true">InertGases</h4><ul><li><p>Addinganinertgas</p></li><li><p>P<em>T=P</em>1+P<em>2</em>+P3…</p></li><li><p>Althoughtotalpressure(P<em>T</p><ul><li><p>Reaction favors reactants.</p></li><li><p>Change in concentration can lead to favoring products.</p></li></ul><h4 id="8ad09a03-98e9-42a7-8a8c-335227ca0e0f" data-toc-id="8ad09a03-98e9-42a7-8a8c-335227ca0e0f" collapsed="false" seolevelmigrated="true">Pressure and Volumes</h4><ul><li><p>Shifts the equilibrium towards products (shifting right).</p></li></ul><h4 id="8c272fb3-3b86-46e4-a0b2-f4642918bef8" data-toc-id="8c272fb3-3b86-46e4-a0b2-f4642918bef8" collapsed="false" seolevelmigrated="true">Inert Gases</h4><ul><li><p>Adding an inert gas</p></li><li><p>P<em>T = P</em>1 + P<em>2</em> + P3…</p></li><li><p>Although total pressure (P<em>T) is increa

  • Adding an inert gas will not shift the equilibrium.

    • Volume Changes

    • Kp=K(RT)ΔnK_p = K(RT)^{\Delta n}

    • Δn = n(products) - n(reactants)

    • K=Kp(RT)−ΔnK = \frac{K_p}{(RT)^{-\Delta n}}

    • Decreasing volume increases concentration: []=nV[] = \frac{n}{V}

    • Decreasing volume will shift the equilibrium to the right (reducing volume favors reducing number of moles).