Question

NaOH was titrated to the phenolphthalein endpoint with a known concentration of HCl. The student conducting the experiment placed 12.97 mL of 2.74 M HCl in a beaker with the indicator. Before beginning the reaction, he noted that the buret read a volume of 4.50 mL. After reaching the endpoint, the buret read 13.65 mL. Calculate the molarity of NaOH that reacted upon reaching the endpoint. Be sure to report your answer to the appropriate number of significant figures.

Answer 1

Answer:

The concentration of NaOH solution is 3,65M

Explanation:

The neutralization of NaOH with HCl is:

NaOH + HCl → NaCl + H₂O

You are titrating 12,67 mL HCl 2,74M with your NaOH solution, the moles of HCl in the beaker are:

12,67 mL ≡ 0,01267L×$\frac{2,74 moles}{1L}$ = 0,0347 moles HCl ≡ 0,0347 moles NaOH

The volume that you require for total neutralization of 12,67 mL HCl 2,74M is:

13,65 mL - 4,50 mL = 9,50 mL ≡ 0,0095L

Thus, the concentration of NaOH solution is:

$\frac{0,0347 moles}{0,0095L}$ = 3,65M

I hope it helps!