Nothing Essay

2838 WordsFeb 23, 201512 Pages
ABSTRACT A molecular diffusion experiment was conducted with the goal of determining the diffusion coefficient of acetone into air. For this experiment, acetone was placed in a capillary tube and was allowed to diffuse into non-diffusing air that was passed over the test tube at the temperature of 40oC. The temperature is kept constant and air stream is passed over the top of the tube to ensure that the partial pressure of the vapor is transferred from the surface of the liquid to be air stream by molecular diffusion. The initial reading and every 2 minutes subsequent reading of the liquid acetone level are determined, and the experiment is conducted for 10 minutes. The experiment is repeated by changing temperature to 45 oC and50 oC. A graph of t/L-Lo against L-Lo is plotted and best fit of straight line and slope of the graph are obtained. The diffusivity of acetone at two different temperatures is determined through calculation. The diffusivity of acetone at temperature of 40 oC, 45 oC and 50 oC are 8.415 x 10-5 m2/s , 3.6006x 10-8 m2/s and 2.3980 x 10-8 m2/s respectively. Throughout the experiment, the diffusivity of acetone is determined to be higher at higher temperature. This fits the theory where temperature affects the diffusion rate. Several recommendation should be taken during operating this experiment to minimize the errors. INTRODUCTION Mass transport in a gas or liquid generally involves the flow of fluid (e.g. convection currents) although atoms also diffuse. Solids on the other hand, can support shear stresses and hence do not flow except by diffusion involving the jumping of atoms on a fixed network of sites. Diffusion can be divided into two types which are diffusion in a uniform concentration gradient and diffusion in a non-uniform concentration. Uniform concentration obeys Fick’s first law where the constant of proportionality is called the

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