Equilibrium¶
| Name | Symbol | Unit |
|---|---|---|
| Activity | a | - low solute concentration: a = concentration nearly pure liquids / solids: a = 1 gases: a = PGas (bar) |
| Equilibrium constant (only depends on the temperature) | K_{eq} / K | - |
| Reaction quotient (same as K_{eq} except the system is not at equilibrium) | Q | - |
| Solubility product Constant (a special K_{eq} which focuses on solubility) | K_{sp} | - |
| Equilibrium constant for autoionization of water | K_w=1.00\times10^{-14} | |
| Molar solubility | [ ] | M or \frac{mol}{L} |
| Equation | Explain |
|---|---|
| K_{eq}=\frac{a^y_Da^z_E}{a^w_Ba^x_C} | This equation calculates the K_{eq} for wB + xC <-> yD + zE a^y_D means the activity of D to the power of its coefficient If any of the reactant / product is liquid / solid, their activity is 1, so they are removed from the equation. |
| K_{forward}=\frac{1}{K_{reverse}} | |
| K_{sp}=[B^+_{(aq)}]^x[C^-_{(aq)}]^y | This equation calculates the K_{sp} for BC (s) <-> xB+ (aq) + yC- (aq) The square brackets means the concentration of |
| Q vs K_{eq} | Reaction |
|---|---|
| Q=K_{eq} | Equilibrium |
| Q<K_{eq} | Forward reaction |
| Q>K_{eq} | Reverse Reaction |
Le Chatelier's Principle¶
Changes in the temperature, pressure, volume, or concentration of a system will result in opposing changes in the system in order to achieve a new equilibrium state.
| Stress | Shift |
|---|---|
| Increase the concentration of a substance | away from substance |
| Increase the pressure of the system | towards reaction produces fewer moles |
| Increase the temperature of the system | towards endothermic reaction |
| Catalyst | no shift |
endothermic reaction / \Delta H > 0: requires energy
exothermic reaction / \Delta H < 0: releases energy
ICE Table¶
Given: P_{H_2} = 0.2bar; P_{I_2} = 0.2bar; K_{eq} = 35
- List ICE Table
| H2 (g) | + | I2 (g) | <-> | 2HI (g) | |
|---|---|---|---|---|---|
| Initial | 0.2 | 0.2 | 0 | ||
| Change | -x | -x | +2x | ||
| Equilibrium | 0.2 - x | 0.2 - x | +2x |
- Substitute the equilibrium line to K_{eq} equation:
K_{eq} = \frac{P^2_{HI}}{P_{H_2}P_{I_2}}
$35=\frac{(2x)^2}{(0.2-x)(0.2-x)}$
x=0.16
Rule of 100¶
If \frac{\text{[initial reactant]}}{K_{eq}} > 100:
Change of reactants is negligible
K_{eq}=\frac{x^2}{b-x}\approx\frac{x^2}{b}
Solubility¶
| Q_{sp} vs K_{sp} | Satuated | Form Precipitate |
|---|---|---|
| Q_{sp} = K_{sp} | yes | no |
| Q_{sp} < K_{sp} | no | no |
| Q_{sp} > K_{sp} | yes | yes |
Last update:
December 8, 2021
Created: September 19, 2021
Created: September 19, 2021