1.) A compound has two amino/aminium groups and one carboxyl/carboxylate group.
ID: 1090243 • Letter: 1
Question
1.) A compound has two amino/aminium groups and one carboxyl/carboxylate group. The respective pKas are 8.1, 10.1, and 2.1. To the nearest tenth of a unit, what is the isoelectric point of this compound?
2.) A compound has two carboxyls and one aminium group. The pKas of the groups are 1.9, 4.7, and 8.5, respectively. A biochemist has 100 mL of a 0.10 M solution of this compound at a pH of 6. She adds 39 mL of 0.1 M NaOH. To the nearest hundredth of a unit, what will be the pH of the solution after addition of the NaOH (assume full stirring to reach a new equilibrium)?
3.) What is the pH (to the nearest hundredths) of a 0.13 M solution that was made with the sodium salt of a carboxyl-containing organic compound? The pKa of the acidic form of this compound is 4.61.
Explanation / Answer
The isoelectric point is the point where the net charge on the compound is zero.As in the given compound there are two basic groups (amino) hence the isoelectric point will be at higher value of pH (>7) .
The isoelectric point will be at (8.1+10.1)/2 =9.1
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