MCB 32L Lab Reports

# MCB 32L Lab Reports - Jae Shin Wendy Ingram Lab Report#1...

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Jae Shin 09/21/10 Wendy Ingram Lab Report #1 Lab 1: Movement of Electrolytes Across an Artificial Membrane I. Introduction Background : There are two things that determine the potential difference across a membrane: the concentration of ions on either side of the membrane and the permeability of the membrane. Cations are membranes permeable to only positive charges; anions are permeable to only negative charges. The presence of a selective membrane to charge can produce a voltage difference across that barrier. This voltage difference is an equilibrium condition called the Nernst potential. The equation describing the equilibrium Nernst potential is written below: it is important to note that this calculation is only valid for the case where one ion is membrane permeant and the other ion is membrane impermeant. E_x = RT/ZF x ln [X]a/[X]b E_x = Nernst potential or equilibrium voltage for ion X across the membrane R: gas constant = 8.31 Volt Coulomb/KMol T: Temperature Z: charge of the ion F: Faraday constant= 9.61 x 10^4 Coulomb/Mol [X]a: concentration of permeable ion on side A [X]b: concentration of permeable ion on side B For this experiment, an artificial cation or anion-selective membranes will be used to examine the electrochemical phenomena associated with creating a voltage difference across a membrane. Hypothesis : My hypothesis for this experiment is that if solutions of different concentrations are placed on either side of a semi-permeable membrane that is permeable to only one ion, then the voltage difference (Nernst equation) across the membrane will change as the concentration of the permeable ion is changed on one side of the barrier.

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II. Materials and Methods A cation selective and an anion selective membrane, each permeable to only positive and negative ion, respectively, were placed between two Lucite blocks with chambers on each of the membrane, on top of the vise. Solutions of different concentrations were placed on
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MCB 32L Lab Reports - Jae Shin Wendy Ingram Lab Report#1...

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