Litmus Paper Copyright 2007 Pearson Benjamin Cummings All

p. H Paper p. H 0 1 2 3 4 5 p. H 7 8 9 10 11 12 6 13

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Desired Features of Sensors p. H paper 1904 p. H 0 1 2 3 4 5 p. H 7 8 9 10 11 12 6 13 Detection limit Low deflection High sensitivity High selectivity Wide dynamic range Simple to use Cost-effective

Range and Color Changes of Some Common Acid-Base Indicators p. H Scale 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Indicators Methyl orange Methyl red Bromthymol blue Neutral red Phenolphthalein red 3. 1 – 4. 4 red 4. 4 yellow 6. 2 red colorless 6. 8 yellow 7. 6 8. 0 blue yellow 10. 0 red Bromthymol blue indicator would be used in titrating a strong acid with a strong base. Phenolpthalein indicator would be used in titrating a weak acid with a strong base. Methyl orange indicator would be used in titrating a strong acid with a weak base. colorless beyond 13. 0

p. H Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

INDICATOR COLORS IN TITRATION Indicator Acid color Transition color Base color STRONG ACID – STRONG BASE Litmus 2 p. H Bromthymol blue 3 4 5 6 7 8 9 10 11 12

INDICATOR COLORS IN TITRATION Indicator Acid color Transition color Base color WEAK ACID – STRONG BASE Phenolphthalein 2 p. H Phenol red 3 4 5 6 7 8 9 10 11 12

INDICATOR COLORS IN TITRATION Indicator Acid color Transition color Base color STRONG ACID – WEAK BASE Methyl orange 2 p. H Bromphenol blue 3 4 5 6 7 8 9 10 11 12

Indicator 1 2 Orange IV 4 5 6 Colorless Phenolphthalein Methyl Red 3 Red Orange Peach Orange 7 8 9 10 11 12 Pink Yellow Red

Common p. H Indicators Zumdahl, De. Coste, World of Chemistry 2002, page 520

Edible Acid-Base Indicators COLOR CHANGES AS A FUNCTION OF p. H INDICATOR p. H 2 3 4 5 6 7 8 9 10 11 12 RED APPLE SKIN BEETS BLUEBERRIES RED CABBAGE * CHERRIES GRAPE JUICE RED ONION YELLOW ONION PEACH SKIN PEAR SKIN PLUM SKIN RADISH SKIN RHUBARB SKIN TOMATO TURNIP SKIN *YELLOW at p. H 12 and above

Red Cabbage Indicator Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

H+ Phenolphthalein Indicator Colorless = Acidic p. H Pink = Basic p. H

-O O C C OH HO C O- O (Colorless acid form, HIn) C OH O- O (Pink base form, In-)