Chemistry 160 Laboratory 2

Chemistry 160
LABORATORY 2
Standardization of NaOH and HCl

PRE-LABORATORY ASSIGNMENT: Complete and turn in the Pre-Laboratory Assignment from the module "Preparation of a Standard Sodium Hydroxide Solution".

EQUIPMENT: Check out one 5 mL pipet, two (2) 250 mL Erlenmeyer flasks (to give you a total of three) and one 50 mL analytical buret for the titrations. Rinse the buret thoroughly at least three times with distilled water before returning it at the end of the day. You will also use one of the hot plates in the lab.

PROCEDURE: You will use the standardized NaOH from Part I to standardize an HCl solution. Both standardized solutions will be used later in Laboratory #4, Evaluations of Commercial Antacids. So don't discard them!

PART I - Standardization of NaOH against KHP: follow the procedure in the module "Preparation of a Standard Sodium Hydroxide Solution". EXCEPTIONS: The procedure calls for duplicate determinations. Do it THREE times instead and add the values for the third determination to the module's report sheet. Also, use 0.4 g of KHP per sample, not 3 g. (The normality of the NaOH in the procedure is ~0.1 N, whereas the normality of NaOH needed for Laboratory #4 is ~1 N. Therefore, the NaOH stock solution you will be given is an analytical 10:1 dilution of ~1 N NaOH. You will use the original 1 N stock solution for Laboratory #4.)

PART II - Standardization of 0.6 N HCl

Obtain about 20 mL of 0.6 N HCl in a clean, dry beaker.

Pipet three 5.00 mL portions of the 0.6 N HCl into 250 mL Erlenmeyer flasks. Dilute to about 50 mL with distilled water, add 2 drops of phenolphthalein and titrate with the standardized 0.1 N NaOH solution to the end point.

Calculate the normality of the HCl and report your values using the Report Sheet.

Turn in both Report Sheets to your Teaching Assistant

This page was edited Friday, October 03, 2003