CHEM-C 117 Lecture Notes - Lecture 9: Acid Strength, Reaction Quotient, Equilibrium Constant
Document Summary
For cis-2-butene trans-2-butene, looking at reactant and product concentrations after long periods of time, we see reaction does not go to completion. (cid:1870)(cid:1853)(cid:1872)(cid:1857)(cid:3033)(cid:3042)(cid:3045)=(cid:1863)(cid:3033)(cid:3042)(cid:3045)[(cid:1855)(cid:1871)] and (cid:1870)(cid:1853)(cid:1872)(cid:1857)(cid:3045)(cid:3032)(cid:3049)=(cid:1863)(cid:3045)(cid:3032)(cid:3049)[(cid:1872)(cid:1870)(cid:1853)(cid:1866)(cid:1871): at equilibrium, (cid:1870)(cid:1853)(cid:1872)(cid:1857)(cid:3033)(cid:3042)(cid:3045)=(cid:1870)(cid:1853)(cid:1872)(cid:1857)(cid:3045)(cid:3032)(cid:3049) [(cid:3002)](cid:3276)[(cid:3003)](cid:3277: subscript (cid:1829) indicates equation in terms of concentration. If [(cid:1827)],[(cid:1828)](cid:883: ex. (cid:884) (cid:1834)(cid:2870)+(cid:1841)(cid:2870) (cid:884) (cid:1834)(cid:2870)(cid:1841) (cid:1834)(cid:3045)(cid:3041)= (cid:886)(cid:890)(cid:885). (cid:888)(cid:883) (cid:1863)(cid:1836: ex. (cid:1840)(cid:2870)+(cid:1841)(cid:2870) (cid:884) (cid:1840)(cid:1841) In general, do not write units for (cid:1837); units for concentration always (cid:3040)(cid:3042)(cid:3039)(cid:3013: ex. Consider cis-2-butene trans-2-butene; starting with pure cis or pure trans will reach. [(cid:3030)(cid:3046)] ; has same mathematical form as (cid:1837), but put in initial. If we start with mixture of cis and trans, what direction will reaction proceed to reach equilibrium: enthalpy change most important factor in determining direction, but not only thing equilibrium either way. At any point in time: concentrations instead of equilibrium. Predicting reaction direction (fast) (slow) approximation: occurs with excess cis-2-butene, occurs with excess trans-2-butene. Currently accepted mechanism: second step that it does not disturb equilibrium.
