Sequence A: How to Solve a Kp/Kc Problem

1. Write the balanced chemical equation for the equilibrium.
2. Identify which species are gaseous (for Kp) or aqueous/gaseous (for Kc); omit pure solids and liquids.
3. Count $\Delta n$ = (moles of gaseous products) − (moles of gaseous reactants).
4. Apply Kp = Kc(RT)^$\Delta n$ using R = 0.0821 L·atm/(mol·K) and T in Kelvin.
5. Check units: Kp has units of (atm)^$\Delta n$; confirm sign of $\Delta n$ matches the shift in K magnitude.

Sequence B: How to Predict Equilibrium Shift (Q Method)

1. Write the equilibrium expression (same form as K).
2. Substitute the CURRENT (non-equilibrium) concentrations to calculate Q.
3. Compare Q with K: Q < K → forward; Q > K → backward; Q = K → equilibrium.
4. Identify which direction reduces Q toward K.
5. State which concentrations increase and decrease as a result.

Sequence C: Buffer Preparation

1. Choose a weak acid with pKa within 1 unit of the target pH.
2. Calculate required [salt]/[acid] ratio: log([salt]/[acid]) = pH − pKa.
3. Dissolve calculated moles of weak acid and its conjugate salt in water.
4. Verify using Henderson-Hasselbalch: pH = pKa + log([salt]/[acid]).
5. Adjust with small amounts of strong acid or base if needed.

Sequence D: Solving Ksp and Solubility

1. Write the dissolution equilibrium and its Ksp expression.
2. Identify if a common ion is present in the solution.
3. Set up ICE table: common ion provides initial concentration; s = solubility = increase.
4. Apply simplifying assumption: s ≪ [common ion] if common ion is ≥ 100× more concentrated.
5. Solve for s algebraically; verify the approximation holds.