Rates, Equilibria and Further Organic Chemistry

WCH14Unit 45 topics · 16 questions

Key equations

The relationships this unit leans on most. Check your formulae or data booklet for which ones the exam gives you.

4.4Acid-base equilibria3 questions

rate equation; orders $m$ , $n$ come from experiments

$t_{1/2} = \dfrac{\ln 2}{k}$

first-order reactions have a constant half-life

$\ln k = -\dfrac{E_a}{RT} + \ln A$

Arrhenius: plot $\ln k$ against $1/T$ , gradient $-E_a/R$

$\Delta S_{\text{total}} = \Delta S_{\text{system}} + \Delta S_{\text{surroundings}}$: feasible when $\Delta S_{\text{total}} > 0$
$\Delta S_{\text{surroundings}} = -\dfrac{\Delta H}{T}$
$\Delta G = \Delta H - T\Delta S_{\text{system}}$: feasible when $\Delta G < 0$
$\Delta G = -RT\ln K$: links free energy and the equilibrium constant

$K_c = \dfrac{[\text{C}]^c[\text{D}]^d}{[\text{A}]^a[\text{B}]^b}$: for $a\text{A} + b\text{B} \rightleftharpoons c\text{C} + d\text{D}$ ; only temperature changes it
$p_A = x_A \times p_{\text{total}}$

with $\Delta H$ in J mol $^{-1}$

Δ

G

<

0

total

partial pressure from the mole fraction, for $K_p$

$1.00\times10^{-14}\,\text{mol}^2\,\text{dm}^{-6}$ at 298 K

+

]

[

A−

]

acid dissociation constant; $\text{p}K_a = -\log K_a$

weak acid, assuming little dissociates