══════════════ PC-06 CHEAT SHEET — EQUILIBRIUM ══════════════

▸ Kc = [P]^p[Q]^q / [A]^a[B]^b (equilibrium concentrations; omit solids/liquids)
▸ Kp = Kc(RT)^$\Delta n$ | $\Delta n$ = gaseous products − gaseous reactants
▸ $\Delta G$° = −RT ln K | K > 1 → $\Delta G$° < 0 (products favoured)

▸ Q < K → forward | Q > K → backward | Q = K → equilibrium

LE CHATELIER QUICK REF:
  Conc. / Pressure change → shifts position; K unchanged
  Temperature change      → shifts position; K CHANGES
  Catalyst                → NO shift; NO K change
  Inert gas (const. V)    → NO effect
  Inert gas (const. P)    → shifts toward MORE gas moles

pH FORMULAS:
  pH = −log[$H^{+}$] | pOH = −log[$OH^{-}$] | pH + pOH = 14 @ 25°C
  Kw = 10^{-14} @ 25°C
  Weak acid: [$H^{+}$] = √(Ka·C)
  Buffer: pH = pKa + log([salt]/[acid])  ← Henderson-Hasselbalch
  Ka × Kb = 10^{-14} (conjugate pair @ 25°C)

SALT HYDROLYSIS:
  SA + SB → pH = 7  |  SA + WB → pH < 7  |  WA + SB → pH > 7
  WA + WB → pH = 7 + ½pKa − ½pKb

Ksp RULES:
  Ksp = [cation]^m [anion]^n
  Precipitation: ionic product > Ksp
  Common ion → solubility DROPS dramatically
  AgCl: s = √Ksp | $Ag_{2}CrO_{4}$: s = (Ksp/4)^(1/3)

TOP NEET TRAPS:
  ① Catalyst → never shifts equilibrium
  ② Inert gas const. V → no effect
  ③ pH of 10^{-8} M HCl ≠ 8 (≈ 6.98)
  ④ pH = 7 neutral ONLY at 25°C
  ⑤ Ka·Kb = Kw (not Ka + Kb)
  ⑥ Ksp of $Ag_{2}CrO_{4}$ = [$Ag^{+}$]^{2} [$CrO_{4}^{2-}$] (exponent = 2, not 1)
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