Question { UPL, 27705 }

Why pH range is maximum 14.0

Answer

As you all know ,we measure pH of all of samples in
water.And the reaction of water is
H<+ + OH<- ------> H20
In this equilibration constant kw is
[H+] [OH-] = Kw = 1 X 10-14
By applying -log on both sides
-log [OH-] - log [H+] = 14
You know pH= - log [H+]
Therefore, pH = 14 - (-log [OH-])

You can see from this equation that the higher than
concentration of OH- ions, the lower the value of -log [OH-
]. If the concentration of OH- ions reaches 1 mol/dm3 , the
value of -log [OH-] is zero, which, according to the
equation, gives pH=14.0.
However, if the concentration of OH- ions exceeds 1 mol/dm3
(which is very rare), the value of -log [OH-] would be
negative, which, according to the equation, gives a pH of
greater than 14.0.

Therefore, the pH range does not necessarily have a maximum
of 14.0, since there is no limit to the concentration of a
base.

Question { 9331 }

In UV-VIS spectrophotometer:My diluent is methanol even
though i corrected base line for methanol,In my sample scan
i found methanol peak.what is the reason?

Answer

My diluent is only methanol(AR Grade).i got peak at 205nm
which is of AR Grade methanol.We are all very well know
that we get the peak for AR Methanol about 205nm and for
commercial methanol about 210nm.

Question { 10609 }

perchloric acid&glacal acetic acid both are acids but
reaction is complete in volumetric titrations.how?

Answer

Perchloric acid is Very strong acid
Acetic acid is weak acid
In presence of very strong acid like pechloric acid
acetic acid bahaves as a base and accepts a proton(H+) from
perchloric acid and forms CH3COOH<2+
Non aqaous titrations are used to titrate the samples
which are very weak bases or salts of weak bases.So in our
titration we take a weak base sample in a titration vessel.

By taking protons from perchloric acid, acetic acid behaves
like a strong acid in presence of a weak base. So reaction
occurs between strong acid and a weak base.
Role of acetic acid:
1.In presence of strong perchloric acid it behaves like a
base and accepts protons.
2.In presence of weak base it behaves as a strong acid and
donates protons to weak base.Protons transfer from
perchloric acid to weak base through acetic acid.

Perchloric acid-------->acetic acid--------->weak base
Finally it is strong acid weak base titration but not acid
acid titration.

Question { 9580 }

today i am doing calibration of HPLC. when i inject the
blank it was going on -ve.(bleow then zero) why?

Answer

Negative peak simply indicate that your mobile phase
absorbs UV light.So use only HPLC grade solvents.Even with
HPLC grade solvents you get the negative peaks you system
might not be working properly.

Regards
M.KIRAN REDDY

Question { Hetero, 56378 }

WHAT IS THE DIFFERENT BETWEEN PURITY, POTENCY AND ASSAY

Answer