The average titration volume of the 0.09876 M NaOH used in back titration is 29.59 ml. Calculate the number of mmoles of HCl in the 250 ml volumetric flask.

The number of moles of HCl in the 250 mL volumetric flask is 0.003 moles

Explanation:

Firstly, we solve for the concentration of acid using the formula

CaVa/CbVb = nₐ/nb

where Ca is the concentration of acid

Cb is the concentration of base

Va is the volume of acid

Vb is the volume of base

nₐ is the number of moles of acid (from the equation)

nb is the number of moles of base (from the equation)

Ca × 250/0.09876 × 29.59 = 1/1

Ca = 0.09876 × 29.59/250

Ca = 0.012 M

To determine the number of moles of HCl acid present in the 250 ml volumetric flask, the formula for molarity is used

Molarity = number of moles ÷ volume (in liter or dm³)

Volume needs to be converted to liter; 250 ml ⇒ 0.25 L

Molarity of the acid is 0.012 M

From the formula above, number of moles = molarity × volume (in liter)

number of moles = 0.012 × 0.25

number of moles of acid = 0.003 moles