Hello!
You'll need 20 mL of 0,20 M NaOH to react completely with 100 mL of 0,040 M Acetic Acid.
The reaction between NaOH and Acetic Acid is the following:
NaOH + CH₃COOH → H₂O + CH₃COONa
To calculate the volume of 0,20 M NaOH needed to react completely with 100 mL of 0,040 M Acetic Acid, we'll need to use the following equation (Molar equivalence) and clear for Volume of NaOH:
[tex]M_{NaOH}*V_{NaOH}=M_{CH_3COOH}*V_{CH_3COOH} \\ \\ V_{NaOH}= \frac{M_{CH_3COOH}*V_{CH_3COOH} }{M_{NaOH}} \\ \\ V_{NaOH}= \frac{0,040M*100 mL }{0.20}}=20 mL[/tex]
Have a nice day!
