Critical Solution Temperature (CST), Determine the conc. of Sodium chloride in Phenol Water System

Summary

This experiment focuses on determining the concentration of sodium chloride in a solution by observing the critical solution temperature (CST) of a phenol-water system. Participants prepare varying concentrations of sodium chloride and mix them with 80% phenol, followed by heating the mixtures to observe the temperatures at which they become a single layer. The temperatures, T1 and T2, are recorded, allowing for the calculation of unknown concentrations through graphical extrapolation. This method illustrates the relationship between solute concentration and critical solution temperature in a hands-on laboratory setting.

Takeaways

• 😀 The experiment aims to determine the concentration of sodium chloride using the critical solution temperature (CST) of a phenol-water system.
• 📦 Preparation of a phenol solution requires mixing 80 mL of pure phenol with 20 mL of distilled water to achieve an 80% volume by volume concentration.
• 🧪 A 1% sodium chloride solution is prepared by dissolving 1 gram of sodium chloride in 100 mL of distilled water.
• 🔍 Test tubes are labeled for different concentrations: 0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1%, with specific volumes of sodium chloride solution added to each.
• 💧 To each test tube, 5.5 mL of phenol solution is added, along with 2.5 mL of the corresponding sodium chloride solution.
• 🔥 The test tubes are placed in a water bath heated to approximately 80°C for temperature observation.
• 🌡️ The temperature at which the opalescence in the solution disappears is recorded as T1, while the temperature when it reappears is noted as T2.
• 📊 The average of T1 and T2 is calculated for each concentration to determine the critical solution temperature.
• 📈 A graph is plotted with concentration on the x-axis and CST on the y-axis to analyze the relationship between the two.
• ❓ The unknown concentration is identified by extrapolating the graph based on the observed data.

Q & A

What is the primary objective of the experiment described in the transcript?

The primary objective is to determine the concentration of sodium chloride in a given solution using the critical solution temperature (CST) of a phenol-water system.

How is the 80% phenol solution prepared?

The 80% phenol solution is prepared by mixing 80 ml of pure phenol with 20 ml of distilled water.

What concentration of sodium chloride solution is prepared for the experiment?

A 1% sodium chloride solution is prepared by dissolving 1 gram of sodium chloride in 100 ml of distilled water.

What volumes of sodium chloride solution are transferred to the test tubes for different concentrations?

The volumes transferred are 10 ml for 0%, 2 ml for 0.2%, 4 ml for 0.4%, 6 ml for 0.6%, 8 ml for 0.8%, and 10 ml for 1% concentration.

What safety precautions should be taken when handling phenol?

One should handle phenol with care to avoid skin contact, as it can cause burns. Wearing personal protective equipment (PPE), such as gloves and goggles, is also advised.

What is the significance of the temperatures T1 and T2 noted during the experiment?

T1 is the temperature at which the opalescence in the solution disappears, indicating the critical solution temperature (CST), and T2 is the temperature at which the opalescence reappears upon cooling.

How is the concentration of an unknown sodium chloride solution determined?

The concentration of an unknown sodium chloride solution is determined by extrapolating the graph plotted from the known concentrations and their corresponding CST values.

Why is it important to ensure that all test tubes contain exactly 10 ml of total solution?

Ensuring that all test tubes contain exactly 10 ml is crucial for maintaining consistent experimental conditions, which is necessary for accurate comparisons and calculations.

What type of graph is drawn to analyze the results of the experiment?

A straight-line graph is drawn with sodium chloride concentration on the x-axis and the critical solution temperature on the y-axis.

What visual change indicates that the solution is no longer separated into two layers?

The disappearance of opalescence indicates that the solution has become a single homogeneous layer, signaling the critical solution temperature.