Question

To determine the molar mass of an organic acid, HA, we titrate 1.030 g of HA with standardized NaOH. Calculate the molar mass of HA assuming the acid reacts with 36.58mL of 0.380 M NaOH according to the equation

HA(aq) + NaOH(aq) → NaA(aq) + H₂O(ℓ)

Answer 1

Consider a reaction between HA and NaOH as

HA _(aq) + NaOH _(aq) → NaA _(aq) + H₂O _(l)

1 mol 1 mol 1 mol 1 mol

From reaction , it is clear that 1 mole HA reacts With 1 mole NaOH.

We know that , Molarity (M) = no. of moles / volume of solution in litre

no. of moles of NaOH = Molarity x volume of solution in litre

= 0.380 moles / L x 0.03658 L

= 0.0139 moles .

Therefore no. of moles of HA= 0.0139 moles .

Again we know that , no of moles = mass / molar mass

Molar mass = mass / no of moles

= 1.030 gm / 0.0139 moles .

= 74.1 gm / mole