The Antoine Equation given in equation 5 can be used to approximate vapor pressure for a given compound at a given temperature: [5] where is vapor pressure of the compound, T is temperature, and A, B, and C are p constants (12). This equation is generally accurate within 10% for temperatures ranging from the triple point to the critical point. RESULTS The masses of the experimental compounds were collected at half-hour intervals from time lapse photographs and entered into Microsoft Excel to track diffusion over time (Fig. 6). Most data sets demonstrated nearly perfectly linear diffusion, while others had more noticeable variances; nonetheless, the data showed excellent correlation with zero-order diffusion (r2>0.99). Some of the liquids with higher diffusion coefficients had masses that suddenly leveled off and stopped displaying zero order diffusion rates. This was caused by the complete evaporation of all the liquid, preventing the vapor pressure from remaining constant. Such data was excluded when determining the line of best fit and r2 values. Figure 6 (Primary Data for n-Octane): The gravimetric data collected for n-Octane Compounds Table 2 shows the various compounds that were tested, sorted by polarity class and molecular size, and the average diffusion coefficient that was calculated. By manipulating Fick’s law and taking measurements of the membrane thickness, vapor pressure, and mass lost over the time period (Fig. 6), the diffusion coefficients for the various compounds could be calculated. For the 1-hexanol and 1-heptanol, we were unable to collect reliable data from the second trial of each substance. The data was very erratic and could not be quantifiable so the average diffusion coefficient for those two substances was calculated using only one trial. The diffusion coefficients were plotted and a linear relationship was observed, with the diffusion coefficient increasing along with the molecular size. For all three polarity classes of compounds, a linear, positive correlation was seen between molecular size and the diffusion coefficient (Fig. 7). Table 2: Diffusion Coefficients of the Various Compounds Average Flux Thickness of Average Diffusion Substance (g m-2 hr-1) Membrane Coefficient (m2 s-1) (μm) Alkanes Pentane Trial 1 5.685 66 16.05
The Antoine Equation given in equation 5 can be used to approximate vapor pressure for a given compound at a given temperature: [5] where p is vapor pressure of the compound, T is temperature, and A, B, and C are constants (12). This equation is generally accurate within 10% for temperatures ranging from the triple point to the critical point. RESULTS The masses of the experimental compounds were collected at half-hour intervals from time lapse photographs and entered into Microsoft Excel to track diffusion over time (Fig. 6). Most data sets demonstrated nearly perfectly linear diffusion, while others had more noticeable variances; nonetheless, the data showed excellent correlation with zero-order diffusion (r2>0.99). Some of the liquids with higher diffusion coefficients had masses that suddenly leveled off and stopped displaying zero order diffusion rates. This was caused by the complete evaporation of all the liquid, preventing the vapor pressure from remaining constant. Such data was excluded when determining the line of best fit and r2 values. Figure 6 (Primary Data for n-Octane): The gravimetric data collected for n-Octane Compounds Table 2 shows the various compounds that were tested, sorted by polarity class and molecular size, and the average diffusion coefficient that was calculated. By manipulating Fick’s law and taking measurements of the membrane thickness, vapor pressure, and mass lost over the time period (Fig. 6), the diffusion coefficients for the various compounds could be calculated. For the 1-hexanol and 1-heptanol, we were unable to collect reliable data from the second trial of each substance. The data was very erratic and could not be quantifiable so the average diffusion coefficient for those two substances was calculated using only one trial. The diffusion coefficients were plotted and a linear relationship was observed, with the diffusion coefficient increasing along with the molecular size. For all three polarity classes of compounds, a linear, positive correlation was seen between molecular size and the diffusion coefficient (Fig. 7). Table 2: Diffusion Coefficients of the Various Compounds Substance Average Flux (g m-2 hr-1) Thickness of Membrane (μm) Average Diffusion Coefficient (m2 s-1) Alkanes Pentane Trial 1 5.685 66 16.05
T5-Final-Paper.docx