The critical temperatures and pressures of a series of halogenated methanes are as follows: (c) Predict the critical temperature and pressure for CCl4 based on the trends in this table. Look up the experimentally determined critical temperatures and pressures for CCl4, using a source such as the CRC Handbook of Chemistry and Physics, and suggest a reason for any discrepancies.

Key Concepts

Critical Temperature and Pressure

Critical temperature is the highest temperature at which a substance can exist as a liquid, while critical pressure is the minimum pressure required to maintain that liquid state at the critical temperature. Above these values, the substance becomes a supercritical fluid, exhibiting unique properties. Understanding these concepts is essential for predicting phase behavior in substances like halogenated methanes.

Trends in Halogenated Methanes

Halogenated methanes, such as CCl4, exhibit trends in their critical properties based on molecular structure and intermolecular forces. Generally, as the size and number of halogen atoms increase, the critical temperature and pressure also tend to increase due to stronger van der Waals forces. Recognizing these trends allows for informed predictions about the critical properties of similar compounds.

Experimental vs. Theoretical Values

Discrepancies between experimentally determined and predicted critical temperatures and pressures can arise from various factors, including measurement errors, purity of the sample, and the limitations of theoretical models. Understanding these potential sources of error is crucial when comparing predicted values with literature data, as it helps in assessing the reliability of the predictions made.