Preparation and Standardization of a Sodium Hydroxide Solution

Objective/Purpose: The objective of this experiment will be the standardization of sodium hydroxide using potassium hydrogen phthalate by the titration method. Introduction:
The concentration of solutions can be reported in terms of molarity and normality. Molarity is equal to: HCL, HBR, H2SO4, HNO3
M = mol Solute (mol) (Monoprotic) (Diprotic)

V(L)g solutions (L)

M = __N___ for Monoprotic acids molarity = normality molar mass V

One molar solution can be prepared by dissolving the mass of 1 mole of the particular substance in enough water to make a 1L solution.

Monoprotic:
HCL + NaOH  H2O + NaCl

Diprotic:
H2SO4 + NaOH  H2O + Na2SO4

N = __EW__
L EW= molar mass L = number of titratable protons

To perform an acid-base neutralization using the titration technique to determine the concentration (normality) of the NaOH prepared in part A.

C8H5O4K + NaOH H2O + KC8H4O4Na

KHP: KHC8H4O4

*Acid base indicator- substances that have different colors in acidic and basic environments

*Phenolphthalein- colorless in acid and pink in base. The end point of the titration is the first permanent color change.

Materials:
-Sodium hydroxide, Phenolphthalein solution, KHP, Pipette, 10 ml graduated cylinder, large beaker, medium beaker, 25mL volumetric flask, Distilled water, stopper, 10mL burette, ring stand, clamp, analytical balance scale, 25mL Erlenmeyer flask, weighing paper. Method:

A pipette was used to place 10 drops of 6N NaOH solution into a 25mL volumetric flask. The NaOH was then diluted by adding carbon dioxide-free distilled water to the 25mL mark. A 10mL burette was then put clamped onto a ring stand in vertical position. The burette was then rinsed with 1mL portion of the NaOH solution that was prepared in step one. The burette was then filled with a pipette to the zero mark with NaOH.

0.3000 to 0.4000 grams of potassium hydrogen phthalate (KHP) was used as a source for the experiment. A piece of weighing paper was then weighed on the analytical balance scale. 0.0700 to 0.0800g of KHP was placed onto the paper and was then weighed again. The KHP crystals were then transferred to 3, 25mL Erlenmeyer flask’s. 10mL of carbon dioxide-free distilled water was added to each flask and was swirled gently to dissolve all the KHP crystals. 2-3 drops of phenolphthalein were added to all 3 flasks.

The initial volume of the burette was taken down before starting the experiment. The KHP acid solution was then titrated using the NaOH solution prepared in step one drop by drop. The titration stopped when the solution turned permanently pink. The final volume was then recorded for trial one. This procedure was then repeated two more times for the rest of the trials. With the information obtained, the normality of the NaOH solution was then calculated.

Results: See attached data sheet

Discussion/Conclusion:
After conducting the experiment we were able to perform an acid-base neutralization using the titration technique to determine the concentration (normality) of the NaOH prepared in part A. After calculating the normality we noticed that values of the 3 trials was a bit greater than 10%. Some errors that we may take into account are user error. Maybe when adding the NaOH solution to the acid, we may have added too much drops and thus got a darker pink color. Another error that we may have encountered is not stopping the dropper up to the meniscus. These are some errors that may have altered our results.