IB›IB Chemistry HL›Mind mapsR3.1 Proton transfer reactionsIB Chemistry HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsAcids and basesBrønsted–Lowry acid donates a protonBase accepts a protonConjugate pair differs by one protonAmphiprotic: acts as both, e.g. HX2O\ce{H2O}HX2OStrong acids ionise fullypH and KwpH=−log10[H+]\text{pH} = -\log_{10}[\text{H}^+]pH=−log10[H+]Kw=1.00×10−14K_w = 1.00 \times 10^{-14}Kw=1.00×10−14 at 298 KpH+pOH=14.00\text{pH} + \text{pOH} = \mathbf{14.00}pH+pOH=14.00[OH⁻] = 1.63 × 10⁻³ gives pH 11.21Ka and KbKa=[H+][A−][HA]K_a = \frac{[H^+][A^-]}{[HA]}Ka=[HA][H+][A−]Larger Ka, smaller pKa: stronger acidKa×Kb=KwK_a \times K_b = K_wKa×Kb=KwWeak acid: [H+]=Ka×c[H^+] = \sqrt{K_a \times c}[H+]=Ka×cStronger acid → weaker conjugate baseProton transferacids, bases and bufferspHKaK_aKaKwK_wKwSalt pHIons of strong acids/bases do not hydrolyseNHX4X+\ce{NH4+}NHX4X+ salts are acidicEthanoate and carbonate salts are basicHydrogencarbonate is weakly basicTitration curvesStrong + strong: equivalence at pH 7Weak acid + strong base: equivalence > 7Half-equivalence: pH = pKaWeak + weak: no steep sectionIndicator changes colour at pH ≈ pKa(HIn)BuffersResist pH change on adding small acid or alkaliWeak acid plus its conjugate baseAdded H⁺ removed by the base componentpH=pKa+log10[A−][HA]\text{pH} = \text{p}K_a + \log_{10}\frac{[A^-]}{[HA]}pH=pKa+log10[HA][A−]Dilution barely changes pH, but capacity falls