Question

1.342 g of a solid white acid are dissolved in water and completely neutralized by the addition of 37.18 mL of 0.376 M NaOH. Calculate the molar mass of the acid, assuming it to be a monoprotic acid.

Answer 1

HA + NaOH -----> NaA + H₂O

1 mole of acid reacts with 1 mole of base. (or) no. moles of acid = no. moles of base

No. moles of base used is:

No. moles = Molarity x volume in L

     = 0.376 moles/L x 0.03718 L

    = 0.01398 moles.
No. of moles acid = g/ GMW

GMW = g /no. moles of Acid

           = 1.342g / 0.01398 moles

           = 95.99 g/mol   = 96 g/mol              

Hence, the molar mass of the acid = 96 g/mol