Elizabeth Lee
James Poland
CHEM 104A
21 September 2014
Discussion and Conclusion of Experiment #4: States of Matter Sleuth
Discussion
The results of this experiment enabled the experimenter to determine the identity of an unknown salt (#3) using ion-exchange chromatography by analyzing the inorganic salts of the unknown salt, which can be examined by acid-base titration using ion-exchange resin. The stationary phase is made up of acid groups which will attach to the resin, which is then rinsed down the column with water. The mobile phase contains the inorganic salt dissolved in a solvent, which is then added to the column. As it goes down the column, an exchange of H+ ions and cations occur. The solution collected at the bottom of the column contains the acid form of the inorganic salt. This can be titrated to determine the number of moles. Once equilibrium hits, the number of moles and weight of the sample can be determined. …show more content…
The analytic balances may not always be “zeroed”: some of the balances kept fluctuating between -.05 to 0.5, which would affect the accuracy of the weight of the sample. A prominent issue that occurred throughout the lab was air bubbles present in the columns. If the column of resin was not perfectly uniformed, the experiment must restart, or else the ion-exchange chromatography will not perform accurately. Another issue was the titration of the inorganic salt solution. If the solution turned into a bold pink/purple, then too much NaOH was added, and the true number of moles and weight of the sample cannot be determined. Overestimating the amount of NaOH needed will underestimate the weight of the
James Poland
CHEM 104A
21 September 2014
Discussion and Conclusion of Experiment #4: States of Matter Sleuth
Discussion
The results of this experiment enabled the experimenter to determine the identity of an unknown salt (#3) using ion-exchange chromatography by analyzing the inorganic salts of the unknown salt, which can be examined by acid-base titration using ion-exchange resin. The stationary phase is made up of acid groups which will attach to the resin, which is then rinsed down the column with water. The mobile phase contains the inorganic salt dissolved in a solvent, which is then added to the column. As it goes down the column, an exchange of H+ ions and cations occur. The solution collected at the bottom of the column contains the acid form of the inorganic salt. This can be titrated to determine the number of moles. Once equilibrium hits, the number of moles and weight of the sample can be determined. …show more content…
The analytic balances may not always be “zeroed”: some of the balances kept fluctuating between -.05 to 0.5, which would affect the accuracy of the weight of the sample. A prominent issue that occurred throughout the lab was air bubbles present in the columns. If the column of resin was not perfectly uniformed, the experiment must restart, or else the ion-exchange chromatography will not perform accurately. Another issue was the titration of the inorganic salt solution. If the solution turned into a bold pink/purple, then too much NaOH was added, and the true number of moles and weight of the sample cannot be determined. Overestimating the amount of NaOH needed will underestimate the weight of the