Question

It takes 26.8 mL of a 0.0700 M NaOH standard solution to neutralize a 250 mL sample of lactic acid (C3H6O3). What mass of lactic acid was dissolved in the sample?

Answer 1

The complete balanced chemical reaction for this would be:

NaOH  +  C3H6O3  -->  NaC3H5O3  +  H2O

 

So we see that exactly 1 mole of NaOH reacts with 1 mole of lactic acid.

Calculate moles of NaOH.

moles NaOH = 0.07 moles/L * 0.0268 L

moles NaOH = 1.876 x 10^-3 mol

 

So,

moles C3H6O3 = 1.876 x 10^-3 mol

The molar mass of lactic acid is 90.08 g/mol so the mass is:

mass C3H6O3 = (1.876 x 10^-3 mol) * 90.08 g/mol

mass C3H6O3 = 0.169 g