Introduction
The purpose of this experiment was to analyze and interpret the results of a
chemical reaction to determine the relationship between reactants and
products through titration. Volumetric analysis, a precise quantitative
technique, was employed to measure the volumes of solutions involved in
the reaction. The hypothesis was that the relationship between the reactant
concentrations could be quantified accurately using titration and
standardization techniques. This study is significant as it demonstrates the
practical applications of stoichiometry and chemical equilibria in determining
unknown concentrations of substances. The experiment involved the
neutralization of an acid with a base using a suitable indicator to identify the
endpoint, ensuring the reaction reached completion.
Method
The experimental procedures were conducted as outlined in the proposal
from Part A. A burette was rinsed and filled with a sodium hydroxide solution
of known concentration. Using a pipette, a measured volume of hydrochloric
acid was transferred to a conical flask. A few drops of phenolphthalein were
added to the acid solution as an indicator. The sodium hydroxide solution
was then titrated against the hydrochloric acid while constantly swirling the
flask until the endpoint, marked by a faint pink color, was achieved. The
initial and final burette readings were recorded for each trial. The experiment
was repeated multiple times to ensure accuracy and reliability of the results.
All measurements and observations were documented.
Results
The data collected during the experiment are summarized below:
Trial Initial Burette Final Burette Volume of NaOH
Reading (cm³) Reading (cm³) Added (cm³)
Roug 0.0 22.7 22.7
h
1 0.0 21.6 21.6
2 0.0 21.7 21.7
3 0.0 21.5 21.5
The average volume of NaOH used was calculated as: $$\text{Average
Volume} = \frac{(21.6 + 21.7 + 21.5)}{3} = 21.6 \, \text{cm³}.$$
The molar concentration of HCl was determined using the formula: C_1V_1 =
C_2V_2,$$ where:
C1=concentration of NaOH (0.1 mol/dm³),C_1 = \text{concentration of
NaOH (0.1 mol/dm³)},
V1=average volume of NaOH (0.0216 dm³),V_1 = \text{average
volume of NaOH (0.0216 dm³)},
V2=0.025 dm³ (volume of HCl),V_2 = 0.025 \, \text{dm³ (volume of
HCl)},
C2=concentration of HCl (unknown).C_2 = \text{concentration of HCl
(unknown)}.
Solving for C2C_2: $$C_2 = \frac{C_1 \cdot V_1}{V_2} = \frac{0.1 \cdot
0.0216}{0.025} = 0.0864 \, \text{mol/dm³}.$$
The mass concentration was calculated as: $$\text{Mass Concentration} = \
text{Molarity} \times \text{Molar Mass of HCl} = 0.0864 \times 36.46 = 3.15
\, \text{g/dm³}.$$
Discussion
The results confirmed the hypothesis by demonstrating the precise
relationship between the known and unknown concentrations through
titration. The balanced reaction equation: $$\text{NaOH(aq) + HCl(aq) →
NaCl(aq) + H₂O(l)}$$ illustrates the 1:1 molar ratio between sodium
hydroxide and hydrochloric acid. The calculated molar concentration of HCl
was 0.0864 mol/dm³, and its mass concentration was 3.15 g/dm³.
The data showed consistency across trials, with minimal deviation in the
volumes of NaOH used. This reliability indicates that the procedure was
conducted carefully and systematically. The use of phenolphthalein, which
changes from colorless to faint pink at the endpoint, proved effective in
identifying the completion of the reaction. The results align with theoretical
expectations and emphasize the practical utility of volumetric analysis in
determining unknown concentrations accurately.
Limitations
Potential sources of error in the experiment include:
1. Human error in observing the meniscus while recording burette
readings.
2. Difficulty in identifying the exact color change at the endpoint, leading
to slight over-titration.
3. Environmental factors such as fluctuations in temperature, which could
affect the reaction rate. Precautions taken included ensuring the
burette and pipette were free of air bubbles and cleaning all apparatus
before use. However, limitations such as reliance on subjective color
perception for the endpoint and potential contamination of the
solutions remained.
Reflection
This experiment demonstrated the importance of titration in real-world
applications, such as in industrial processes for quality control of chemical
products. The knowledge gained enhances the understanding of
stoichiometry and its role in accurate chemical quantification. The findings
are relevant to society, as similar principles are applied in water quality
testing and pharmaceutical formulation. Adjustments such as performing
more trials and using an automated titrator to eliminate human error could
improve precision in future experiments. The use of appropriate scientific
language and meticulous documentation throughout this lab further
reinforces the value of clear communication in science.
Conclusion
The experiment successfully determined the molar and mass concentration
of hydrochloric acid as 0.0864 mol/dm³ and 3.15 g/dm³, respectively.
These findings support the hypothesis and highlight the effectiveness of
volumetric analysis in quantifying unknown concentrations. The results
validate the accuracy and reliability of the titration method used.
