Laboratory Report: Determination of Sodium Hydroxide Concentration through Acid-Base Titration

Acid-base titration is a widely used technique in analytical chemistry to determine the concentration of a solution by reacting it with a standard solution. In this experiment, the goal is to determine the concentration of a sodium hydroxide (NaOH) solution by titrating it with hydrochloric acid (HCl) and sulfuric acid (H2SO4) solutions. The neutralization reaction involved is:

HCl+NaOH→H2​O+NaCl

The stoichiometry of this reaction allows us to determine the concentration of NaOH based on the amount of HCl used in the titration.

The endpoint of the titration will be detected using phenolphthalein as an indicator.

Apparatus:

• Volumetric flask: 250 mL
• Filter funnel
• Erlenmeyer flask
• Beaker: 1, 250 mL
• Burette: 1, 50 mL
• Pipette: 1, 25 mL

Chemical Reagents: a) 100 mL 1.000 × 10^-2 M HCl solution
b) 100 mL 1.000 × 10^-2 M H2SO4 solution
c) 10 mL C solution containing NaOH (with pipette)
d) Phenolphthalein solution

Procedure:

1. Preparing the Solutions:
   • Measure 100 mL of 1.000 × 10^-2 M HCl solution and 100 mL of 1.000 × 10^-2 M H2SO4 solution. Dilute each in a 250 mL volumetric flask.
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   • Measure 10 mL of solution C containing NaOH using a pipette.
2. Titration Procedure:
   • Calibrate the burette by rinsing with distilled water and then with a small volume of HCl solution. Fill the burette with HCl solution and record the initial volume.
   • In a 250 mL Erlenmeyer flask, add 10 mL of NaOH solution (solution C) and a few drops of phenolphthalein.
   • Begin titration by slowly adding HCl solution from the burette with constant swirling.
   • Observe the color change; the appearance of a persistent pink color indicates the endpoint.
   • Record the final volume of the burette.
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3. Repeat Titration:
   • Repeat the titration process at least two more times to ensure accuracy and consistency in results.
4. Calculations:
   • Calculate the average volume of HCl solution used in the titrations.
   • Use the stoichiometry of the neutralization reaction to determine the moles of NaOH reacted.
   • Calculate the concentration of the NaOH solution.
5. Results and Analysis:
   • Present the average volume of HCl used and the calculated concentration of the NaOH solution.
   • Construct a table displaying the raw data, calculations, and results.
   • Discuss any discrepancies or sources of error in the experiment.
6. Conclusion:
   • Summarize the findings and discuss the precision and accuracy of the experimental method.
   • Suggest improvements or modifications for future experiments.

Calculations and Formulas:

1. Molarity Calculation:
   •  (L)Molarity(M)=volume of solution (L)moles of solute​
2. Stoichiometry:
   • Use the balanced chemical equation to relate moles of reactants and products.
3. Average Volume:
   • Number of TrialsAverageVolume=Number of TrialsSum of Volumes​

The results obtained from the titration experiments are presented in the table above. The average volume of HCl used can be used to calculate the moles of NaOH reacted and subsequently the concentration of the NaOH solution.

In conclusion, the experiment successfully determined the concentration of a sodium hydroxide solution through acid-base titration. The calculated concentration provides valuable information about the accuracy of the laboratory technique used. Any variations or discrepancies observed during the experiment should be discussed to improve the overall understanding of the procedure.

By following the outlined steps and calculations, this laboratory serves as an educational tool for students learning about acid-base titrations and analytical chemistry techniques. The inclusion of tables, calculations, and a detailed procedure ensures a comprehensive understanding of the experiment and its outcomes.

Hydrochloric Acid (HCl) and Sodium Hydroxide (NaOH) Titration:

Trial 1: HCl​=MV=0.1×1.4=0.14mol

From the balanced chemical equation HCl+NaOH→NaCl+H2​O, it is evident that 1 mol of HCl reacts with 1 mol of NaOH.

Concentration of NaOH, M=Vn​=250.14​=0.0056M

Standard deviation =0.0056−0.00450.0045×100=24.44=0.00450.0056−0.0045​×100=24.44

Trial 2: HCl​=MV=0.1×1.0=0.10mol

Concentration of NaOH, M=Vn​=250.10​=0.0040M

Standard deviation =0.0040−0.00450.0045×100=11.11=0.00450.0040−0.0045​×100=11.11

Trial 3: HCl​=MV=0.1×1.0=0.10mol

Concentration of NaOH, M=Vn​=250.10​=0.0040M

Standard deviation =0.0040−0.00450.0045×100=11.11=0.00450.0040−0.0045​×100=11.11

Average Concentration of NaOH (HCl titration): =0.0056+0.0040+0.00403=0.0045 M=30.0056+0.0040+0.0040​=0.0045M

Sulfuric Acid (H2SO4) and Sodium Hydroxide (NaOH) Titration:

Trial 1: H2SO4​=MV=0.1×1.1=0.11mol

Concentration of NaOH, M=Vn​=250.11​=0.0044M

Standard deviation =0.0044−0.00640.0064×100=−31.25=0.00640.0044−0.0064​×100=−31.25

Trial 2: nH2SO4​=MV=0.1×0.6=0.06mol

Concentration of NaOH, M=Vn​=250.06​=0.0024M

Standard deviation =0.0024−0.00640.0064×100=−62.5=0.00640.0024−0.0064​×100=−62.5

Trial 3: nH2SO4​=MV=0.1×0.7=0.07mol

Concentration of NaOH, M=Vn​=250.07​=0.0028M

Standard deviation =0.0028−0.00640.0064×100=−56.25=0.00640.0028−0.0064​×100=−56.25

Average Concentration of NaOH (H2SO4 titration): =0.0044+0.0024+0.00283=0.0032 M=30.0044+0.0024+0.0028​=0.0032M

Discussion:

1. The negative standard deviations in the H2SO4 titration suggest that there might be systematic errors or inconsistencies in the experimental procedure. Further investigation is needed to identify and rectify these issues.
2. The average concentrations of NaOH in both titrations are comparable, indicating the reliability of the experimental technique.
3. The precision of the experiment can be improved by increasing the number of trials and using more accurate measuring instruments.
4. The concentration of the NaOH solution calculated from HCl titration is consistent, while the results from H2SO4 titration show more variability, emphasizing the importance of repeated experiments.

In conclusion, the laboratory successfully determined the concentration of a NaOH solution through titration with HCl and H2SO4. The results provide valuable insights into the accuracy and precision of the experimental technique, paving the way for further refinement of the procedure.

For the reaction between H2SO4 with NaOH

Titration is a widely-used technique to determine the concentration of a solution with unknown molarity or the number of moles in a given sample. It relies on a fast and complete chemical reaction with a determinable endpoint. Acid-base titrations, particularly involving strong acids and bases, are common examples of this method.

In the experiment described, hydrochloric acid and sulfuric acid are used as acid substances, and sodium hydroxide is the base substance with an unknown concentration. The concentrations of both acids are stated to be 0.1 M. The endpoint of the titration is signaled by an indicator, in this case, phenolphthalein. The reactions involved are between HCl and NaOH and between H2SO4 and NaOH, producing salts and water.

The difference in the reactions lies in the ionization of the acids. HCl is a monoprotic acid, yielding one H+ ion per molecule, while H2SO4 is a diprotic acid, releasing two H+ ions per molecule. This distinction leads to variations in the amount of acid needed for titration, with diprotic acids requiring less.

However, the experiment faced some challenges, such as overshooting the endpoint during the titration, resulting in higher volumes used. This can be addressed by titrating slowly and ensuring thorough cleaning of glassware to prevent contamination. Despite the imprecise and inaccurate results, the standard deviation indicates a range of 0.0045 M to 0.0065 M. Trial 2 and 3 of the titration with HCl and solution C (NaOH) are considered more acceptable with a concentration of approximately 0.004 M, while the titration using H2SO4 suggests an accepted concentration of 0.0056 M for solution C (NaOH).

In conclusion, titration is a reliable method for determining concentrations and moles of substances, but careful attention to experimental details is crucial for obtaining accurate results.