Acid-Base Titration Arhenius Acid HA → H⁺ A⁻ Acid are species that can donate proton, H⁺ Base BOH → B⁺ + OH⁻ Base are species that can donate hydroside ions, OH⁻ Neutralisation is the reaction between an acid and a base: H⁺ + OH⁻ →H₂O Bronsted Acid → it can donate proton, H⁺ Base → it can accept proton, H⁺

Choosing A Titrant In theory, any strong acid or strong base can be used as titrant. The reason for this is the most reaction involving a strong acid or strong base is QUANTITATIVE.

Strong And Weak Acid Titrant Strong acid titrant Hyrochloric acid (HCl) Nitric acid (HNO₃) Sulphuric acid (H₂SO₄) Perchloric acid (HClO₄) Phosphoric acid (H₃PO₄) Weak acid titrant Acetic acid, (CH₃COOH) Ammonium ion, (NH₄⁻) Hydrogen flouride, (HF) Carbonic acid, (H₂CO₃) Nitrous acid, (HNO₂)

Strong And Weak Base Titrant Strong base titrant Sodium hydroxide, NaOH Potassium hydroxide, KOH Magnesium hydroxide, Mg(OH)₂ Barium hydroxide, Ba(OH)₂ Weak base titrant Ammonium hydroxide, NH₄OH Amine acetate Carbonate, CO₃ ¯ Flouride ion, Fˉ Sodium carbonate, NaCO₃

Equivalent Point The point in the reaction at which both acid and base have been consumed. Neither acid nor base is present in excess End Point Actual result obtained by observations of sudden change of physical properties

End Point vs. Equivalent Point End Point -The point at which the reaction is observed to be completed -The end point signal frequently occurs at some point other than the equivalent point -Refers to point at where the indicator changes colour in the titration Equivalent Point or stoichiometric point -The point at which the equal amount of titrant is added to the analyte -Point at which the reaction is supposedly to complete

Equivalent point End Point

pH mL of Base added 7 Strong acid with strong Base Equivalence at pH 7

Titration of a strong acid by a strong base Titration curve for the titration of mL of M HCl (a strong acid) with the M NaOH (a strong base). Sudden sharp changes of pH Slow change of pH

pH mL of acid added 7 l Strong base with strong acid l Equivalence at pH 7

Indicator – substance that changes color at (or near) the equivalence point MEANING change color just after the equivalence point of a titration end point(color change). FUNCTION The color change is most often detected VISUALLY. Most acid-base indicators are organic dye molecules (either acids or bases.) CHARACTERISTICS

Selecting And Using Indicators Middle half of the pH transition range Overlap the pH at equivalence point / pH at the steepest part of the titration curve At equivalence point (true and point)

Common Name Transition rangeColor ACID Change BASE Crystal violet0.1 – 1.5YellowBlue Thymol blue1.2 – 2.8RedYellow Mrthyl yellow2.4 – 4.0RedYellow Methyl orange3.1 – 4.4RedYellow Bromocresol green3.8 – 5.4YellowBlue Methyl red4.2 – 6.3RedYellow Chlorophenyl red4.5 – 6.4YellowRed Bromothymol blue6.0 – 7.6YellowBlue Phenol red6.4 – 8.0YellowRed Thymol blue8.0 – 9.6YellowBlue Phenolpthalein8.0 – 9.7ColorlessPink Alizarin yellow10.0 – 12.0ColorlessViolet ACID-BASE INDICATORS

Strong Acid With Strong Base  Do the stoichiometry.  mL x M = mmol  They both dissociate completely.  The reaction is H + + OH -  HOH  Use [H + ] or [OH - ] to figure pH or pOH