NEET PG Medical – 2018 – Question – 56
At pKa=pH –
a) Conc. of drug is 50% ionic and 50 % non-ionic
b) Absorption of drug is 50% ionic and 50% ionic
c) Conc. of drug is 75% ionic and 25 % non-ionic
d) Conc. of drug is 25% ionic and 75 % non-ionic
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Correct Answer – A
Answer: A – Concentration of drug is 50% ionic & 50 % Nonionic
Numerically equal pKa & pH represents 50% drug ionization
- pKa is negative logarithm of acidic dissociation of weak electrolyte.
- On equal concentrations of ionized & unionized drugs, log 1 is zero.
- Thus, when pKa is numerically equal to pH
- (pKa=pH)→ 50 % drug is ionized.
