Question

calculate the pH ofa solution prepared by mixing 50.0 ml of 0.200 m ch2h3o2 and 50 ml of 0.100 m Naoh.[ka(ch3cooh)=1.8*10^-5]

Answer 1

I don't know what you tried to write; my best guess is that you have CH3COOH and NaOH. I will call CH3COOH HAc.
millimols CH3COOH = 50 mL x 0.200 M = 10
millimols NaOH = 50 x 0.1 = 5
...........CH3COOH + NaOH ==> CH3COONa + H2O
I..............10................0.................0
add.............................5..............................
C..............-5..............-5...................+5
E...............5...............0.....................5
So you have a buffered solution. Use the Henderson-Hasselbalch equation.
Post your work if you get stuck.

Answer 2

Yes

Answer 3

don't understand