1 answer
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I'm assuming this is meant to be a buffer problem.
.............H2CO3 + KOH ==> KHCO3 + H2O
I..............0.1 mol....0...................0............0
add........................0.04.........................
C............-0.04.......-0.04..........+0.04
E..............0.06..............0...............0.04
Plug the E line into the Henderson-Hasselbalch equation
Post your work if you get stuck.