Page 17 - PC 101 practical notes 24-25..
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MANSOURA NATIONAL UNIVERSIY
PHARM D- CLINICAL PHARMACY LEVEL I PHARM. ANAL. CHEM. I (PC 101)
2. Phenolphthalein (ph.ph.):
• pH range ≈ (8.5 – 10) approximately.
• We use 10 drops of it in our experiments.
• Color:
Colorless * Pink
pH 0 8.5 10 14
Acidic E.P. Basic
to ph.ph. to ph.ph.
*Color of ph.ph. at E.P.:
-If the solution before starting titration is Colorless (i.e. acidic to ph.ph.)
E.P. is First Pink Color persistent for 30 seconds.
-If the solution before starting titration is Pink (i.e. basic to
ph.ph.) E.P. is First Colorless.
Remember:
ph.ph. (small letters) is phenolphthalein indicator
while
+
pH (p small, H capital) is a measure of acidity or alkalinity { = –log [H ] }
Question: Complete the following:
Color of M.O. in water is yellow while color of ph.ph. in water is colorless.
Example of acid-base reactions:
NaOH + HCl → NaCl + H 2O
(basic) (acidic) (neutral {pH=7})
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