Question

The standardization of a sodium hydroxide solution against potassium hydrogen phthalate (KHP) yielded the accompanying results.

Mass KHP/g	0.7987	0.8365	0.8104	0.8039
Volume NaOH/mL	38.29	39.96	38.51	38.29

a. Write the balanced equation occurring between HCl(aq) and NaOH(aq).

b. It takes 15 mL of 0.125M NaOH to reach the end point of the reaction. How many moles of NaOH have you added?

c. What is the mole ratio between HCl and NaOH? How many moles of HCl were in the titrated sample?

d. At the beginning of the titration, there were 22mL of HCl. What was the original concentration of HCl?

Answer 1

a)

balanced equation :

HCl (aq)   + NaOH (aq)    ---------------> NaCl (aq) +   H2O (l)

b)

moles of NaOH = 15 x 0.125 / 1000

moles of NaOH = 1.875 x 10^-3 mol

c)

mole ratio between HCl and NaOH = 1 :   1

moles of NaOH = moles of HCl

moles of HCl = 1.875 x 10^-3

d)

moles of HCl = 1.875 x 10^-3

22 x 10^-3 x C = 1.875 x 10^-3

C = 0.0852

original concentration of HCl = 0.0852 M