biochemistry q - quansar

[ArchivalUser]

you have a basic drug with pka at 8, if you want to get a solution with 99% of the drug in diassociated form, what ph you will need to go to??

1. pH 8,
2. pH9
3. pH 10
4. pH 11
5. pH 7
6. pH 6
7. pH 5

you have a acidic drug with pka at 5, if you want to get a solution with 99% of the drug in diassociated form, what ph you will need to go to??

1. pH 7,
2. pH6
3. pH 5
4. pH 4
5. pH 3
6. pH 2
7. pH 1

[ArchivalUser]

for base...99% dissociated(ionized) means...1%non ionized..which refers to -2..so pH-pK=-2
means pH=-2+8 ..it should be 6.

for acid: 99 % dissociated means 1% non ionized which is +2 so pH=5+2 + 7

is it right??

[ArchivalUser]

you are right
1. answer 6
2. answer 1

[ArchivalUser]

agreed

[ArchivalUser]

not correct

[ArchivalUser]

sorry, for q2, the answer at ph7 is correct

[ArchivalUser]

Could you please explain this once again?
Thanx

[ArchivalUser]

for base, NH3+===NH2+H+

NH2 is the diassociate form so you will need to raise the pH above PKA


for acid, ROOH====ROO- + H+

ROO- is the diassociate form so you will also need to raise the pH above PKA