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PH Indicators. Litmus Paper Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

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Presentation on theme: "PH Indicators. Litmus Paper Copyright © 2007 Pearson Benjamin Cummings. All rights reserved."— Presentation transcript:

1 pH Indicators

2 Litmus Paper Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

3 pH Paper pH pH

4 Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

5 Desired Features of Sensors pH paper 1904 Detection limit Low deflection High sensitivity High selectivity Wide dynamic range Simple to use Cost-effective pH pH

6 Range and Color Changes of Some Common Acid-Base Indicators Indicators pH Scale Methyl orange red 3.1 – 4.4 yellow Methyl red red yellow Bromthymol blue yellow blue Neutral red red yellow Phenolphthalein colorless red colorless beyond 13.0 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.

7 Copyright © 2007 Pearson Benjamin Cummings. All rights reserved. pH

8 Indicator Acid color Transition color Base color Litmus Bromthymol blue STRONG ACID – STRONG BASE pH INDICATOR COLORS IN TITRATION

9 Indicator Acid color Transition color Base color Phenolphthalein Phenol red WEAK ACID – STRONG BASE pH INDICATOR COLORS IN TITRATION

10 Indicator Acid color Transition color Base color Methyl orange Bromphenol blue STRONG ACID – WEAK BASE pH INDICATOR COLORS IN TITRATION

11 Indicator Phenolphthalein Methyl Red Orange IV ColorlessPinkRed OrangeYellow OrangePeachYellow

12 Indicator Colors in Titration

13 Common pH Indicators Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 520

14 Edible Acid-Base Indicators COLOR CHANGES AS A FUNCTION OF pH INDICATOR pH 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 pH 12 and above

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

16 Phenolphthalein Indicator Colorless = Acidic pH Pink = Basic pH H+H+

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


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