Preparation of Experimental Apparatus and Freezing Point Determination of Lauric Acid
Mass of freezing point depression apparatus
Mass of freezing point depression apparatus with lauric acid
Mass of lauric acid used
The correct answer and explanation is :
To determine the mass of lauric acid used in the experiment, use the formula:
[
\text{Mass of lauric acid} = \text{Mass of freezing point depression apparatus with lauric acid} – \text{Mass of freezing point depression apparatus}
]
Explanation:
In this experiment, lauric acid ((\text{C}{12}\text{H}{24}\text{O}_2)) is used to study the freezing point depression, an important concept in colligative properties. This process involves preparing the experimental apparatus, melting lauric acid, and determining its freezing point using a temperature vs. time cooling curve.
- Preparation of Apparatus:
- The freezing point depression apparatus typically consists of a test tube containing lauric acid, placed in a controlled water bath with a thermometer.
- The apparatus is first weighed empty to determine its mass.
- Then, lauric acid is added, and the new mass is measured.
- Mass Calculation:
- Using the provided formula, the mass of lauric acid is found by subtracting the empty apparatus’s mass from the total mass after adding lauric acid.
- This value is critical for calculating molality when determining freezing point depression.
- Freezing Point Determination:
- The lauric acid is heated to a liquid state and then allowed to cool.
- The temperature is recorded at regular intervals, and the freezing point is identified as the plateau in the cooling curve.
This experiment demonstrates key principles of thermodynamics and colligative properties, as the presence of solutes (if added later) would further depress the freezing point.
Here is a relevant image illustrating the experimental setup:
Here is an image illustrating the experimental setup for determining the freezing point of lauric acid.