Step 1. Write the balanced equation
#"CH"_3"COOH" + "NaOH" → "CH"_3"COONa" + "H"_2"O"#
Step 2. Calculate the moles of NaOH
#"Moles of NaOH" = "0.030 84" color(red)(cancel(color(black)("dm"^3color(white)(l) "NaOH"))) × "0.128 mol NaOH"/(1 color(red)(cancel(color(black)("dm"^3 color(white)(l)"NaOH")))) = "0.003 948 mol NaOH"#
Step 3. Calculate the moles of #"CH"_3"COOH"#
#"Moles of CH"_3"COOH" = "0.003 948" color(red)(cancel(color(black)("mol NaOH"))) × ("1 mol CH"_3"COOH")/(1 color(red)(cancel(color(black)("mol NaOH")))) = "0.003 948 mol CH"_3"COOH"#
Step 4. Calculate the mass of the #"CH"_3"COOH"#
#"Mass of CH"_3"COOH" = "0.003 948" color(red)(cancel(color(black)("mol CH"_3"COOH"))) × ("60.05 g CH"_3"COOH")/(1 color(red)(cancel(color(black)("mol CH"_3"COOH")))) = "0.2370 g CH"_3"COOH"#
Step 5. Calculate the mass percent of acetic acid.
#"Mass percent" = "mass of acetic acid"/"mass of vinegar" × 100 % = (0.2370 color(red)(cancel(color(black)("g"))))/(5.441 color(red)(cancel(color(black)("g")))) × 100 %#
#= 4.36 %#
