Determination of the Relative Molecular Mass of Chloroform (CHCl3) by Measuring Vapor Density Using the Dumas Method

This experiment aimed to determine the Relative Molecular Mass (Mr) of a volatile compound, specifically chloroform (CHCl3), by measuring its vapor density using the Dumas Method. The fundamental principle of this method is based on the Ideal Gas Law (𝑃𝑉 = 𝑛𝑅𝑇), where is calculated from the known mass of the vapor, the volume of the flask, the temperature, and the pressure. The procedure involved heating the chloroform in a sealed flask until it vaporized completely, replacing the air inside, and then weighing the flask after cooling and condensation. The calculated Mr value for CHCl3 obtained from the experiment was 37.79, which is significantly lower than the theoretical value of 119.5 . This major discrepancy was attributed to systematic errors, such as leakage in the flask's sealing mechanism during heating, leading to the loss of vapor mass, or inaccuracies during air replacement and the cooling process. Consequently, the experimental results did not align with the theoretical expectation that the Dumas method should yield results close to the true value.