52. Titration Curve for Weak Acid & Strong Base Over what pH range does the titrated solution suddenly change from high [H 3 O 1+ ] to high [OH 1- ]? About 6.5 to 11 What’s pH when 0.067 mol NaOH added? pH = 5 What’s [H 3 O 1+ ]? [H 3 O 1+ ] = 1 x 10 -5 M Best Indicator (p. 756 & next slide)? o -Cresolphthalein or Phenolphthalein.
60. Figure 15.8 p. 756: The Useful pH Ranges for Several Common Indicators
61. Color Ranges of Various Indicators Used in Titrations Why are different indicators used for SA-SB, SA-WB, or WA-SB titrations? Each type of titration has a different end point. Is it better to use an indicator with a color change over a wide or narrow pH range. Why? Narrow pH range since gives better approximation of the end point.
62. pH Scale Relationships If [H 3 O 1+ ] of “x” is 10 x greater than another with pH 3, what is pH of “x”? pH = 2 If [OH 1- ] of “y” is 1000 x greater than pure water’s, what is pH of “y”? pH = 10 Is hand soap more or less basic than baking soda? More basic.
63. Figure 15.9 p. 757 The pH Curve for the Titration of 100.0 mL of 0.10 M HCI with 0.10 M NaOH Which is the better indicator? Neither, since their ranges are not close to the equivalence (end) point.
64. Figure 15.10 p. 757 The pH Curve for the Titration of 50 mL of 0.1 M HC 2 H 3 O 2 with 0.1 M NaOH Choose the best indicator between the two . . . Phenolphthalein
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