Explain the Preparation of Sodium Hydroxide
I. PURPOSE OF THE EXPERIMENT
The purpose of this laboratory activity is to prepare a NaOH solution, determine the concentration of the NaOH solution accurately and
precisely, and calculate the % purity of the original solid Naoh. It will be based on the reaction of NaOH with a known solid acid where all reactantswill be dissolved in water. The titration technique, using phenolphthalein as an indicator, will be used to obtain the necessary data for this determination.
II INTRODUCTION
(i) Concentration of solutions:
Although there are many different units of concentration, the most commonly used unit among chemists is morality. Molarity is defined as the number of moles of solute per 1M of solution. The main advantage of molarity as a unit of concentration is therefore the ease with which measurements of the volume of a solution can be combined with the molarity to determine the numberof moles of the solute that are present to take part in a chemical reaction.
(ii) Standardization:
The process of using a known amount of one reagent to determine the concentration of another reagent is known as standardization.
(iii) Acid Base Titration and End Point
Reactions between acids and bases that are dissolved in water occur almost
Instantaneously: they occur as fast as the two solutions can be mixed. These reactions also tend to go to completion: react until the entire
Limiting reagent is consumed. When exact stoichiometric amounts of acid and base have been mixed, the reaction is said to have reached the equivalence point. Essentially all of the acid has reacted with the base, and vice versa. An Indicator is used to determine when an acid has exactly neutralized a base, or vice versa. A suitable indicator changes colors when equivalent amounts of acid and base are present. The color change is termed the end point of the titration.
(iv) Titration
The technique of slowly adding an acid to a base or vice versa until the reaction has reached the equivalence point is known as titration.
III. EXPERIMENTAL
3.1 Chemicals: NaOH pellets, Oxalic acid dihydrate (H2C2O4.2H2O),
Phenolphthalein indicator
3.2 Equipment: Burette, Pipette, Conical flask (Erlenmeyer flask), Pipette bulb, Beakers, Burette stand, clamp etc.
3.3Procedure:
3.3.1 Preparation of approximately NaOH 0.1 M solution
Approximately 2g NaOH was weighed.
250ml of distilled water was put into a clean 500ml volumetric flask.
NaOH pellets were added completely
After all the NaOH pellets had all dissolved, another 250ml of distilled water was added upto the marking
Then the solution was mixed thoroughly.
3.3.2 Standardization of NaOH solution using diprotic acid (oxalic acid) or(Succinic acid)
The standard oxalic acid solution 0.05 M in the burette was placed.
10 mL of NaOH solution was transferred into a 125 mL conical flask with the aid of a pipette.
1-2 drops of phenolphthalein indicator was added and then it was titrated with the standard oxalic acid
. The titration is repeated until duplicate determinations agree within 0.05mL of each other.
All the titration volume was recorded in the table and the following calculated;
(i) Molarity of NaOH solution
(ii) moles of NaOH in 500mL
(iii) mass of NaOH in 500mL
(iv) % Purity of NaOH (s)
IV. RESULTS and DISCUSSIONS
(i) Molarity of prepared NaOH solution = 0.1 M
(ii) Molarity of standardized NaOH solution = 0.097 M
(iii) Moles of NaOH in 500mL = 0.0485 mol
(iv) Mass of NaOH in 500 mL = 1.94 g
(v) % Purity of NaOH(s) = 97 %
Discussion
There is a slight difference between the two values. Previously, we weighed the substances using the electric balance but for this experiment, we used equations and calculations
My friend's values agree with mine. They should be similar because we used the same solution with constant Molarity.
V. Conclusion
The Molarity of standardized NaOH solution and% purity of the solid NaOH was determined to be 0.097M and 97%