TL;DR : given acid color of methyl orange
is red, phenolphtalein is colorless , alkaline color is, yellow and
red , respectively
Wouldn't methyl orange stay Red in color when the end pt of a
SA-WB titration, is at a acidic pH?? Why will methyl orange turn
Yellow at the end pt , that occured at a acidic pH(for pg 157 SA-WB
titration example, end pt pH≈5.5)? (given pH range methyl orange
3.1-4.4)
why/what the reason/mechanism a soln containing an indicator can
suddenly change color when moles of acid = base ??
wouldn't methyl orange be red, phenolphtalein be colorless, at
pH <7 ? also, yellow and red respectively for pH>7?
Wouldn't the indicators already change color at acidic/alkaline
pH before reaching the end point of the reaction?
will phenolphthalein alr change color on the way to
pH ≈ 8.5
for the WA-SB example?
why
will phenolphtalein suddenly turn to pink from colorless at end pt
when moles of acid=base?
and then for WA-WB titration , color change is gradual
This is very confusing. I'm trying very hard to understand the
many numbers and terms here, it's difficult
for example, regarding pg 155, indicator table, and page 157,
the WA-SB titration example
im trying to rationalise this, nt sure if it's correct or not.
here goes;
Basic salt yield pH at end pt greater than 7 (pH≈8.5) .
Titration curve shows a marked change in pH between 7.5 and 10.5(
this means with only few drops of OH- , pH has drastic change)
the end point is within the pH range of
phenolphtalein(8.3-10.0)
if the end pt of the reaction occurs within this pH range, soln
color will turn from colorless to pink
Then there's thia Acid color and Alkaline color column
will phenolphtalein turn red immediately after pH>7 ?
Why will phenolphtalein suddenly turn pale pink at the end pt
when whats left is the salt(CH3CO2-Na+) and H2O?
is it because theres excess acid until eqv. pt (when moles of WA
and SB is the same). but then at eqv pt there's OH- due to
hydrolysis of the basic salt
then shouldn't soln be red in color due to alkaline color of
phenolphtalein is red?
also considering HIn is a WA,
it can also undergo WA-SB reaction
then the color is mixture of the acid color and alkaline
color?
But, only a few drops of indicator added, must this be taken
into consideration?
HIn + H2O 《》H3O+ + In-
HIn + NaOH 《》In-Na+ + H2O
In-Na+ +H2O 《》HIn + Na+ + OH-
