Standardization of Sodium Hydroxide
Chemistry 101 12-STANDARDIZATION OF SODIUM HYDROXIDE
Standard solutions for titrations are especially pure mixtures with exactly known concentrations. Primary standards are very pure solids. They have the advantage that they can be weighed (the analytical balance is normally the most accurate instrument in the laboratory) and they are stable under laboratory conditions. In this experiment, the primary standard is oxalic acid dihydrate, H2C2O4 ( 2H2O. It will be used to standardize a solution of sodium hydroxide.
Sodium hydroxide solutions pick up carbon dioxide from the air. This contamination can affect the strength of the base solution and can spoil the sharpness of the end point in the titration. The procedure below is designed to prepare and standardize carbonate-free NaOH.
Equation 2 NaOH(aq) + H2C2O4 ( 2H2O(s) ( Na2C2O4(aq) + 4 H2O(l)
PROCEDURE
Wear your safety glasses while doing this experiment.
Place 300 mL of deionized water in a large beaker and bring it to the boiling point. Boil it vigorously for 5 minutes and allow it to cool. Repeat with a second 300 mL sample of deionized water.
Clean a 500 mL Florence flask, rinse it twice with 10 to 20 mL of your boiled water, and fit it with a good rubber stopper. Take the flask to your instructor, who will give you about 2.5 mL of 50% NaOH(aq). Fill the flask about two-thirds full with boiled water and mix well, with swirling. Then fill with boiled water to just below the neck and mix again. Label the flask. It now contains about 500 mL of approximately 0.1 M NaOH.
Check out a buret from the stockroom. Rinse it well with tap water, then distilled water. Finally, rinse it three times with about 4 mL of your NaOH solution each time. Fill the buret with NaOH and cover the top of the buret with plastic wrap until you are ready to use it.
Make a data table in your notebook. See the Report Sheet for a list of data entries and calculated quantities.
Standard solutions for titrations are especially pure mixtures with exactly known concentrations. Primary standards are very pure solids. They have the advantage that they can be weighed (the analytical balance is normally the most accurate instrument in the laboratory) and they are stable under laboratory conditions. In this experiment, the primary standard is oxalic acid dihydrate, H2C2O4 ( 2H2O. It will be used to standardize a solution of sodium hydroxide.
Sodium hydroxide solutions pick up carbon dioxide from the air. This contamination can affect the strength of the base solution and can spoil the sharpness of the end point in the titration. The procedure below is designed to prepare and standardize carbonate-free NaOH.
Equation 2 NaOH(aq) + H2C2O4 ( 2H2O(s) ( Na2C2O4(aq) + 4 H2O(l)
PROCEDURE
Wear your safety glasses while doing this experiment.
Place 300 mL of deionized water in a large beaker and bring it to the boiling point. Boil it vigorously for 5 minutes and allow it to cool. Repeat with a second 300 mL sample of deionized water.
Clean a 500 mL Florence flask, rinse it twice with 10 to 20 mL of your boiled water, and fit it with a good rubber stopper. Take the flask to your instructor, who will give you about 2.5 mL of 50% NaOH(aq). Fill the flask about two-thirds full with boiled water and mix well, with swirling. Then fill with boiled water to just below the neck and mix again. Label the flask. It now contains about 500 mL of approximately 0.1 M NaOH.
Check out a buret from the stockroom. Rinse it well with tap water, then distilled water. Finally, rinse it three times with about 4 mL of your NaOH solution each time. Fill the buret with NaOH and cover the top of the buret with plastic wrap until you are ready to use it.
Make a data table in your notebook. See the Report Sheet for a list of data entries and calculated quantities.