Mnemonic 1: OEM — Order vs Molecularity

Order is Experimental; Molecularity is Mechanical

• ORDER → determined from Experiments → can be 0, fractional, integer
• MOLECULARITY → from Mechanism → always 1, 2, or 3
• "You ORDER food experimentally (tasting different items); the restaurant MECHANISM is fixed"

Mnemonic 2: Half-Life Rules — "Zero Depends, First is Free, Second Inverts"

• Zero order: $t_{1}$/{2} = [A]{0}/(2k) → Depends directly on [A]_{0} (more reactant, longer half-life)
• First order: $t_{1}$/{2} = 0.693/k → Free of concentration (always same $t_{1}$/{2})
• Second order: $t_{1}$/_{2} = $\frac{1}{k[A]_{0}}$ → Inverts (more reactant, shorter half-life)

Mnemonic 3: Arrhenius — "A Knight Earns Rest Through work"

• k = rate constant (the Knight)
• A = frequency factor (his Army)
• Ea = activation Energy barrier
• R = gas constant
• T = Temperature
• k = A × e^(−Ea/RT): higher barrier → slower Knight

Mnemonic 4: Completion Shortcuts (First Order)

• 50% done → 1 $t_{1}$/_{2} (half remaining)
• 75% done → 2 $t_{1}$/_{2} (quarter remaining)
• 87.5% done → 3 $t_{1}$/_{2} (eighth remaining)
• 93.75% done → 4 $t_{1}$/_{2} (sixteenth remaining)
• Pattern: n% = 100(1 − $\frac{1}{2}$^m) → m = number of half-lives

Mnemonic 5: Plot Identification — "Zero-Linear, First-Log, Second-Reciprocal"

• Zero order: linear [A] plot
• First order: logarithmic plot (ln[A])
• Second order: reciprocal plot (1/[A])