From these results at constant temperature and

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From these results, at constant temperature and pressure, the molar enthalpy of vaporization (ΔHvap) can be calculated using the relationship between vapor pressure and temperature [ln(Pvap) = -Δvap/RT + C], which is derived from the van’t Hoff equation used for the effect of temperature on the equilibrium constant (ln!!!!=!![!!!!!!]). The molar enthalpy of vaporization is in other words, the amount of energy needed to change one mole of a substance from the liquid phase to the gas phase, at constant pressure and temperature, and is derived by finding plotting ln(P) as a function of 1/T and solving for Δvap= -(slope)(R). The enthalpy of vaporization can then be compared to the literature value to analyze accuracy.
Error AnalysisIn a thoroughly controlled experimental environment, where every procedure or action is precisely and accurately executed, without any chance for error or uncertainty, the percent deviation from the reported literature value for Δvap(40.67 kJ/mole) would have been 0%. That would have meant that the experimental molar enthalpy of vaporization would have been exactly 40.67 kJ/mole. However, this type of environment is extremely difficult to reproduce (almost impossible) and experimental error is inevitable. Because of this the actual Δvap value for the experiment was 43 ± 3 kJ/mole which results in a percent deviation of 5.975%. Although the experiment was performed as directed, experimental difficulties, instrumental uncertainties, assumptions, and human error can all result in a higher, yet more reasonable, percent deviation than that of 0%. Before proceeding in analyzing the errors and uncertainties inherent in the experiment, it should be explained that the values being used for both the error analysis and the graph have been updated and corrected (since incorrect graph data for 1/T was imputed to Chem21Labs). This is not part of the analysis but rather a means to prevent confusion when reading or comparing data). Based on the results, the value of Δvap(43 ± 3 kJ/mole) manifests an uncertainty of 7% in the experimental value. This may have been caused by the accuracies of specific instruments utilized. For example, the accuracy of the 10 mL graduated cylinder used to measure the volume of the bubble is ± 0.1 mL, which shows a range of 1% to 2% uncertainty when comparing the highest value measured (9.35 mL) to the lowest value (4.1 mL); with this it can be concluded that uncertainty increases as volume decreases. Another example includes the accuracy of the yellow digital thermometer, which is ± 0.1°C and represents a range of 0.1% to 3% uncertainty

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