Chemistry
posted by Cristian on .
How much 5M KOH must be added to 1.0 L of 0.1M glycine (pKa 9.6) at pH 9.0 to bring its pH to exactly 10.0?

Use the Henderson Hasselbalch equation twice.
First set of conditions:
pH=9.0
pka=9.6
Solve for the ratio
pH=pka+log[A/HA]
9.0=9.6+log[A/HA]
10^(9.09.6)=[A/HA]
0.25=[A/HA]
Meaning 25% of the solution is protanated, or 0.025 moles is A and 0.075 moles HA
Second set of conditions
pH=10.0
pka=9.6
Solve for the ratio
pH=pka+log[A/HA]
10=9.6+log[A/HA]
10^(10.09.6)=[A/HA]
25.0=[A/HA]
Meaning 25% of the solution is deprotanated, or 0.025 moles is HA and 0.075 moles A
I need to go from 0.025 moles of A to 0.075 moles of A, and I need to go from 0.075 moles of HA to 0.025 moles of HA. This means that I need 0.05 moles of KOH.
5M KOH=0.05 moles of KOH/L
Solve for volume,
0.05 moles of KOH/5M=L of KOH 
Typos
Change 0.025 to 0.25
change 0.075 to 0.75
change 0.05 to 0.5
Everything is correct. 
Never mind, I was correct the first time.