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Published byNorman Horton Modified over 8 years ago
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Measuring pH (and pOH)
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Measuring pH pH can be measured precisely using a pH meter or you could use an indicator
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Bromothymol blue changes from yellow to blue as the pH rises from 6.00 to 7.60 (mid range = green)
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Example Separate samples of a solution of unknown pH cause the following acid base indicator colours Orange IV = yellow Bromothymol blue = blue Phenolphthalein = colourless What is the solution pH? Hint: use the indicator chart at the back of your workbook!
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Modified Arrhenius Acid = a substance that reacts with water to produce H3O+ Base = a substance that reacts to produce OH-
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Example NH3(aq) + H2O Test for acid Test for base More familiar ion?! BASE!
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Example 2 CO2 + H2O Test for acid Test for base More familiar ion = ACID!!
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Example 3 HSO 4 -
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Limitations In some cases, the modified theory cannot predict acid or base because both ions are familiar (i.e. HSO4-)
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Neutralization Acids react with bases to form water and a salt (a neutral ionic compound) i.e. NaOH + HCl H2O + NaCl
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Show the reaction between sodium hydroxide and sulfuric acid
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Ionic Neutralization H3O+ + OH- 2H2O
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Strengths of Acids and Bases Defined in terms of how completely an acid ionizes in water to produce H+
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Strong Acids weak bonds between H+ and the rest of the acid easily gives up its H+ completely
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HClO 4 HI HBr HCl H 2 SO 4 HNO 3 H 3 O +
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Weak Acids Stronger bond with its H+ only partially gives up its H+ example: Vinegar
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Base strength is determined according to its OH- dissociation ease
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Strong Bases Always contains OH- weak bonds between OH- and the rest of the base example: NaOH
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Weak Bases Slightly dissociate into OH- <50% example: NH 3
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Monoprotic Acids Mono form 1 H+ or 1OH- in solution Ex. Show the ionization for Hydogen fluoride: Ex. Show the dissociation of potassium hydroxide:
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Polyprotic Acids Poly form more than 1 hydrogen or hydroxide through a series of steps
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Ex. H3PO4
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