15. PROPERTIES oFACATION EXCHANGE RESIN- Fe\'s UNKNOWN Introduction name!) hange

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15. PROPERTIES oFACATION EXCHANGE RESIN- Fe's UNKNOWN Introduction name!) hange chromatography i used to exchange the ions solution to a catchy attached Ion-exc are attracted to ions covalently phase and replace whatever counter ion was previously attracted to the column material (stationary phase). The stationary phases used in ion-exchange chromatography may be divided into two types: -Sos) attached to cation-exchan contain negatively charged groups (e.g the resin (usually polystyrene), attract positively ions charged anion-exchangers which contain positively charged groups (eg -NGCH attached to the resin, attract negatively charged ions This experiment uses a simple gravi column. The column will contain a cation- exchange resin known as Dowex 50W-x2. Initially, the polymer is preconditioned to contain protons (H) next to each negative site, producing many sulfonic acid groups. Upon exposure of the resin to cations other than H' (such as a Fe solution of unknown concentration), protons are released into the mobile phase when the cations replace them hence the term "cation exchange." The released protons are titrated with a base of known concentration and the concentration of the unknown cation can be determined Experimental Procedure A. Preparation of solutions. Prepare approximately 100 mL of 1 M HCI from the provided 6 M solution measure the appropriate volumes of Hci solution and Nanopure water using a graduated cylinder into a labeled beaker. Prepare -1 L of0.02 M NaoH b dilution of 50 NaoH. Standardize your by ing a solid primary standard at east four times (look back in your book, you have done something like this before) note B. Preparation of stationary phase. Clamp a 0.7 cm x 15 cm glass column from the drawers beneath the Ohaus balances to a buret stand. This cylinder has a porous glass frit. before the tip which the resin spilling out of the It aiso rate of through the is why we are using such a small amount of stationary phase. Check to make sure the column is not clogged by running and a small amount of the hydrochloric acid through it 50W-X2 resin into a small, clean beaker. Add weigh between 1.1 and 1.2 g of Dowex 10 mL (graduated cylinder) 1 M into the beaker regenerate the resin to the fully protonated condition (i saturated with H to groups on the Carefully decant the excess acid from the beaker a approximately ml water and swirl well. Decant "waste beaker". Add rinse water and repeat the wash process 2x. Pl the waste into the "Dowex

Explanation / Answer

1. Never ever let the column be dry, it should always be solvated. A dry colum develops cracks, and the flow of ions gets uneven.

2. While you run the colum try to write the reactions that are occuring and expectd to occur, you will be able to assosciate well with the resin colum and errors might reduce.

I hope this helps.

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