Electrochemistry of Salted and non-Salted Agar, Jello and Gelatin

Introduction: The purpose of this experiment was to determine the optimal configuration for electrochemistry using molds of Agar, Jello, and Gelatin as voltaic salt bridges. The molds were prepared with different concentrations of salts mixed in and with holes indented in which electrolytes were poured.

The solution was then poured into a container. To make the holes for the cells, ring stands were used to hold test tubes in place while the solution solidified. The test tubes were then removed each hole was filled with either were filled electrolytes of AgNO3, PbNO3,, or Cu(NO3)2. The micro-lab voltaic cell was also used to comare with results from the molds.

Results:

Measuring the Voltage:Metal electrodes were placed in their corresponding electrolyte. The leads of the micro-lab voltmeter were clipped to the electrodes to measure the voltage across cells. Below are the voltages measured for each configuration.

Interpretation:Although unexpected, all configurations of molds and electrolytes used produced electricity across the cells, with the voltages similar across the same pair of electrolytes. Even more unexpected was that plain agar produced electricity across its cells. We believed the agar sample used must have been contaminated with some salts. The Gelatin mold, however, was porous and so the electrolytes eventually mixed, thus short-circuiting the voltmeter leads and causing a 0-volt reading.

Preparing the Molds:In preparing the agar, jello, or Gelatin molds, the corresponding powder and a salt (NaOAc, NaNO3, or KNO3) were poured into a beaker of water and boiled.

Grace Gast and Luwa Matthews

Agar beaker “accident”

System Concentration of Salt in Mold/System Conc. of Electrolytes Cu-Ag Cu-Pb Ag-Pbmicro-lab .1M KNO3 .2 M 0.40 0.53 0.89

Round AgarShorter Distance .1M KNO3 .2 M 0.41 0.48 0.88

Longer Distance .1M KNO3 .2 M 0.42 0.48 0.88

Square Agar .1M KNO3 .2 M 0.40 0.47 0.87

Circular Agar .2M KNO3 .2 M 0.39 0.44 0.89

Circular Agar .2M KNO3 .01 M 0.40 0.49 0.85

micro-lab .2M KNO3 .01 M 0.39 0.51 0.91

Jello .1M KNO3 .2 M 0.42 0.45 0.86

Jello None .2M 0.43 0.45 0.85Circular Agar .1M NaOAc .2 M 0.40 0.47 0.88Circular Agar .1M NaNO3 .2M 0.40 0.47 0.85

Gelatin .1M NaOAc .2M None 0.45 0.85Gelatin .1M NaNO3 .2M None 0.45 None

Circular Agar None .2M 0.41 0.45 0.84

System Salt and Concentration Conc. of Electrolytes Cu-Ag Cu-Pb Ag-Pbmicro-lab KNO3 .1M .2 M 0.40 0.53 0.89Round Agar

Shorter Distance KNO3 .1M .2 M 0.41 0.48 0.88Longer Distance KNO3 .1M .2 M 0.42 0.48 0.88

Square Agar KNO3 .1M .2 M 0.40 0.47 0.87Circular Agar KNO3 .2M .2 M 0.39 0.44 0.89Circular Agar KNO3 .2M .01 M 0.40 0.49 0.85micro-lab KNO3 .2M .01 M 0.39 0.51 0.91Jello KNO3 .1M .2 M 0.42 0.45 0.86Jello None .2M 0.43 0.45 0.85Circular Agar NaOAc .1M .2 M 0.40 0.47 0.88Circular Agar NaNO3 .1M .2M 0.40 0.47 0.85Gelatin NaOAc .1M .2M None 0.45 0.85Gelatin NaNO3 .1M .2M None 0.45 NoneCircular Agar None .2M 0.41 0.45 0.84