You will titrate your weak acid unknowns with a solution of NaOH of about 0.10 mol/L. The lowest molecular weight on the list of unknowns is formic acid, MW = 46.03 g/mol. Your titration volume should be between 10 mL and 50 mL. What are the smallest (first answer box) and largest (second answer box) masses of formic acid that would give titration volumes within the limits above? (Note: two significant figures are required)

Question

You will titrate your weak acid unknowns with a solution of NaOH of about 0.10 mol/L. The lowest molecular weight on the list of unknowns is formic acid, MW = 46.03 g/mol. Your titration volume should be between 10 mL and 50 mL. What are the smallest (first answer box) and largest (second answer box) masses of formic acid that would give titration volumes within the limits above? (Note: two significant figures are required)

Answer 1

For 10 mL titration.

volume NaOH used = 10 mL
moles NaOH used M x L = 0.1 x 0.01 - 0.001 moles NaOH.
moles HCOOH used = 0.001
mols HCOOH = g HCOOH/molar mass HCOOH.
0.001 = g/46.03
g HCOOH = 0.001 x 46.03 = 0.04603 which is 0.046 to two s.f.

For the 50 ml:
Done the same way.
moles NaOH = M x L = 0.05 x 0.1 = 0.005
0.005 = g/46.03
g = 0.005 x 46.03 = 0.23015 which rounds to 0.23 grams to two s.f.