A 150ml sample of hydrochloric acid completely reacted with 60.0mL of a 0.100 M NaOH solution. What was the original concentration of the HCl solution

HCl + NaOH = NaCl + H₂O

n (HCl) = c (HCl) v (HCl)

n (NaOH) = c (NaOH) v (NaOH)

n (HCl) = n (NaOH)

c (HCl) v (HCl) = c (NaOH) v (NaOH)

c (HCl) = c (NaOH) v (NaOH) / v (HCl)

c (HCl) = 0.100mmol/mL*60.0mL/150mL=0.040 mmol/mL = 0.040 mol/L

0.040 M HCl