Sketch and explain pH curves for combinations of weak and strong monoprotic acids and bases.

In the subtopic pH curves, titrations and indicators (A-level only), this AQA A-Level Chemistry 7405 learning objective focuses on sketch and explain pH curves for combinations of weak and strong monoprotic acids and bases. It belongs to Acids and bases (A-level only), so revision should stay anchored to this exact subtopic rather than drifting into a generic GCSE-level chemistry summary. Approved keywords to use include pH curve. Monoprotic acid. means an acid that can donate only one proton (H+) per molecule in a reaction Avoid the mistake of students often incorrectly assume that the pH curve for a weak acid-strong base titration will have a steep slope throughout the entire range, similar to that of a strong acid-strong base titration; instead, to correct this, remember that the pH curve for a weak acid-strong base titration will show a more gradual slope before the equivalence point due to the weak acid's partial dissociation. The formula for pH at the equivalence point can be derived from the concentration of the conjugate base formed. For example, if you have a weak acid HA with a concentration of 0.1 mol/dm³ and a Ka of 1.8 x 10^-5, you can calculate the pH at the equivalence point using the formula: pH = 14 - 0.5 * pKa, where pKa = -log(Ka). Substituting gives pH = 14 - 0.5 * 4.74 = 11.63. Therefore, the pH at the equivalence point is 11.63 For exam answers, when sketching pH curves for weak and strong acids, identify the equivalence point and the regions of buffer action