Question

Approximately 7 mL of 6M Noah was diluted to 400 mL and standardized against 0.1135M HCL . the initial volume reading was 0.16 mL for HCL and 0.04 mL for NaOH . upon reaching the pale pink phenolphthalein endpoint, the fine volume reading was 27. 36 for HCL and 35.26 for NaOH . a. what is the molarity of H ion? b. what is volume of acid used in this titration ? c. what is volume of base required to neutralize the acid? d. determine the molarity of OH ion?

Answer 1

Volum of NaOH before dillution = 7 mL

Molarity of NaOH before dillution = 6 M

Moles of NaOH = 6 * 0.007 = 0.042

Final volume of NaOH after dillution = 400 mL = 0.40 L

Final molarity of NaOH = 0.042 / 0.40

= 0.105 M

Molarity of HCl = 0.1135 M

(a). 1 mole HCl on dissociation give 1 mole H+ ion.

So molarity of H+ ion = Molarity of HCl

= 0.1135 M

(b). Initial reading of HCl = 0.16 mL

Final reading of HCl = 27.36 mL

volume of acid used = 27.36 - 0.16

= 27.2 mL

(c). Initial reading of base = 0.04 mL

Final reading of base = 35.26 mL

Volume of base used = 35.26 - 0.04

= 35.22 mL

(d). 1 mole NaOH on dissociation give 1 mole OH- ions.

So molarity of OH- ions = Molarity of NaOh

= 0.105 M