finding the concentration

Question

A 10.0 mL sample of HCl is titrated with 0.105 M NaOH. The initial buret volume is 0.10 mL and the final buret volume is 20.38 mL. What is the concentration (mol/L) of the HCl sample? Answer to 3 decimal places with no units.

Answer 1

At the equivalence point: moles of HCl = moles of NaOH

moles of HCl = molar conc. of HCl x volume of HCl in liter

or moles of HCl = M_aV_a

moles of NaOH = molar conc of NaOH x volume of NaOH in liter.

or moles of NaOH = M_bV_b

at equivalence point: M_aV_a = M_bV_{b. ………} (1)

M_a = ?

V_a = 10.0 mL = 0.0100 L

M_b = 0.105 M

V_b = (final buret reading - initial buret reading)= 20.28 mL = 0.02028 L

substitute the values in equation (1)

M_a x 0.0100 L = 0.105 M x 0.02028 L

Ma = conc of HCl = (0.105M x 0.02028 L) / 0.0100L

= 0.213