Analysis of Baking Soda

Investigation 1

ANALYSIS OF BAKING SODA

『Aim』

 Determine the mass percentage of NaHCO3 in the sample.

『SAFETY』

a. Wear safety goggles and a laboratory apron in the laboratory at all time.

b. Notify your teacher immediately if any chemicals, especially concentrated acid or base, are spilled.

『MATERIALS NEEDED』:

hydrochloric acid, HCl, 12 M (concentrated)

sodium hydroxide, NaOH

phenolphthalein solution

3* 100 mL graduated cylinder

500 mL volumetric flask

2 burets, 25-mL or 50-mL

stirring rod

『BACKGROUND』

Titration is usually the case when insoluble solid reagents are used. Back titration is usually employed for quantitative work with substances of this kind. In this investigation we use back titration to determine the mass of baking soda. Then we can calculate the percent error of the experimenter. The amount of solute can be calculated from the volume of the solution of known concentration. The amount of the unknown may then be found using the balanced equation. Finally the concentration of the second solution used. The three stages involved are closely analogous to those used in reacting mass calculations.

『PROCEDURE:』

A. Preparation of Burets

Rinse a buret with 5 mL of 0.1 M hydrochloric acid solution. Discard the rinse solution. Repeat the rinsing two more times. Fill the buret with 0.1 M HCl solution. Adjust the volume to the zero mark. Rinse a buret with 5 mL of 0.1 M sodium hydroxide solution. Discard the rinse solution. Repeat the rinsing two more times. Fill the buret with 0.1 M NaOH solution. Adjust the volume to the zero mark.

Procedure:

Set up the titration apparatus as shown below

B. Rinse the buret with distilled water, then a small aliquot of base. Fill the

buret with base. Pipette 25 cm3 of 0.10 M acid into a conical flask. Place the pH

meter into the flask and allow it to equilibrate. Record the pH. Now begin

swirling the flask slowly while dripping base into it at a slow rate (about 2

drops/second).

C. Plot this