The Effect of Different Molar Mass on the Diffusion on Substances

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The Effect of Different Molar Mass on the Diffusion on Substances Lunar-maius A. Gaerlan Group 2 Sec. X – 9l August 15, 2012 ABSTRACT The effect of molecular weight on the rate of diffusion was assessed using agar-water gel test. The agar-water gel set up was composed of a petri dish of agar-water gel containing three wells. Drops of potassium permanganate (KMnO4), potassium dichromate (K2Cr2O7) and methylene blue(C16H18N3SCl) were simultaneously introduced to each well. Methylene blue, having the largest molecular weight, displayed the smallest diameter (11 mm) and diffused at the slowest rate (0.20 mm/min.). Next is potassium dichromate with a diameter of 24 mm and rate of diffusion of 0.30 mm/min.. The fastest is the…show more content…
The observations showed that the increase in molecular eight means a decrease in diameter of area of coloration. Table 1.1 In Table 1.2 as time increases, partial rate of diffusion of each substance generally decreases. Within the 30 minute observation, potassium permanganate had the highest average rate of diffusion at the rate of 0.47 mm/min., followed by potassium dichromate (0.30 mm/min.) and methylene blue (0.20 mm/min.). Table 1.2 Potassium permanganate (KMnO4), having the smallest molecular weight, diffused the fastest. It is followed by potassium dichromate (K2Cr2O7), with a molecular weight greater than KMnO4 but less than methylene blue, which has a molecular weight of 374 g/mole. Observations show that as the molecular weight of a substance increases, its rate of diffusion consequently decreases and vice versa. Thus, the hypothesis that the molecular weight is inversely proportional to the rate of diffusion of a substance is supported by the results of the experiment. Some factors may have affected the rate of diffusion of the substances in the experiment which may have led to inaccurate results. Such factors may include but are not limited to inconsistent temperatures and concentrations, the type of medium used, or handling and execution of the experiment SUMMARY AND CONCLUSION The hypothesis, “If the molecular weight affects the rate of diffusion of

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