Titration — weak acid against strong base
25.00 cm³ of 0.100 M ethanoic acid titrated with 0.100 M NaOH: apparatus, the pH trace, and the four landmarks that matter — the acidic start, the buffer plateau, pH = pKa at half-equivalence, and an equivalence point above pH 7.
Rendering…
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{ "id": "probe", "type": "gauge-chart", "label": "Calibrated pH probe and meter", "x": 215, "y": 40, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1", "bold": true },
{ "id": "curve", "type": "line-chart", "label": "pH against volume added", "x": 390, "y": 40, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1", "bold": true },
{ "id": "start", "type": "rounded", "label": "Start pH ≈ 2.9 — weak acid alone", "x": 565, "y": 40, "width": 150, "height": 104, "fill": "#dbeafe", "stroke": "#1d4ed8" },
{ "id": "equiv", "type": "star", "label": "Equivalence 25.00 cm³, pH ≈ 8.7", "x": 740, "y": 40, "width": 150, "height": 104, "fill": "#dcfce7", "stroke": "#15803d", "bold": true },
{ "id": "plateau", "type": "mountain", "label": "Excess NaOH — pH climbs to 12–13", "x": 915, "y": 40, "width": 150, "height": 104, "fill": "#f1f5f9", "stroke": "#475569" },
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{ "id": "flask", "type": "flask", "label": "Conical flask on a stirrer", "x": 215, "y": 200, "width": 150, "height": 104, "fill": "#dbeafe", "stroke": "#1d4ed8" },
{ "id": "buffer", "type": "layers", "label": "Buffer region — pH 3.8 to 5.8", "x": 565, "y": 200, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#a16207" },
{ "id": "salt", "type": "hexagon", "label": "Only CH₃COO⁻ left — it hydrolyses", "x": 740, "y": 200, "width": 150, "height": 104, "fill": "#dcfce7", "stroke": "#15803d" },
{ "id": "hh", "type": "clipboard", "label": "pH = pKa + log([A⁻]/[HA])", "x": 390, "y": 360, "width": 150, "height": 104, "fill": "#f1f5f9", "stroke": "#475569" },
{ "id": "half", "type": "target", "label": "12.50 cm³ → pH = pKa = 4.76", "x": 565, "y": 360, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#a16207", "bold": true },
{ "id": "indicator", "type": "water-drop", "label": "Phenolphthalein (8.2–10.0) fits", "x": 740, "y": 360, "width": 150, "height": 104, "fill": "#ede9fe", "stroke": "#6d28d9" },
{ "id": "wrong", "type": "cross", "label": "Methyl orange (3.1–4.4) misleads", "x": 915, "y": 360, "width": 150, "height": 104, "fill": "#fee2e2", "stroke": "#b91c1c" }
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{ "id": "e2", "source": "pipette", "target": "flask", "label": "aliquot of acid" },
{ "id": "e3", "source": "flask", "target": "probe", "label": "immersed in" },
{ "id": "e4", "source": "probe", "target": "curve", "label": "log every 0.5 cm³", "thickness": 2.5 },
{ "id": "e5", "source": "curve", "target": "start", "thickness": 2.5 },
{ "id": "e6", "source": "start", "target": "buffer", "label": "first additions" },
{ "id": "e7", "source": "buffer", "target": "half" },
{ "id": "e8", "source": "half", "target": "hh", "label": "read pKa here", "style": "dashed" },
{ "id": "e9", "source": "buffer", "target": "equiv", "label": "steep rise", "thickness": 2.5 },
{ "id": "e10", "source": "equiv", "target": "salt", "label": "why pH > 7", "style": "dashed" },
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{ "id": "e12", "source": "indicator", "target": "wrong", "label": "not this one", "style": "dashed" },
{ "id": "e13", "source": "equiv", "target": "plateau", "thickness": 2.5 }
]
}