The ache, or \"burn\", you feel in your muscles during strenuous exercise is cau

Question

The ache, or "burn", you feel in your muscles during strenuous exercise is caused by the accumulation of lactic acid, which has the structure shown below. The hydrogen atom in the COOH grou is acidic, and it can be removed using base to form COOoverline group. To determine the concentration of a solution of lactic acid, a chemist titrates a 22.75 mL sample of it with 0.1010 M NaOH, and finds that 10.32 mL of titrant are required to reach the equivalence point. What is the concentration of the lactic acid solution in moles per liter?

Explanation / Answer

lactic acid is monoprotic acid, menaing it only has 1 proton to donate to solution

so

NaOH + lactic acid = Na+ + Lactate - + H2O

so... ratio is 1:1

mol of NaOH = Mbase*Vbase = 0.1010*10.32 = 1.04232 mmol of NaOH

therefore,

mmol of lactic acid = mmol of NAOH = 1.04232 mmol

M = mmol of lactic acid / Vacid = 1.04232 /(22.75)

M = 0.0458162 M (moles per liter)

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