Introduction; Most chemical reactions are reversible, meaning they react both forward and backward. A forward reaction is generically A + B -> C + D and a reverse reaction is C + D -> A + B. Higher concentrations of A and B at the start of the reaction cause it to move towards C and D before to start. to slow down as more Cs and Ds are created. Eventually, the amount of A and B formed is the same as the amount of A and B used, resulting in a chemical equilibrium, denoted Keq. From this reaction, the equilibrium constant can be calculated using the ratio of the product of the products to the product of the reactants. So Keq= [C]*[D] / [A] * [B]. Some reversible reactions reach equilibrium more quickly than others such as that of the Iron (III) ion (Fe3+) with the thiocyanate ion (SCN-) which forms thiocyanatoiron (III) (FeSCN2+). In this reversible reaction, Fe3+ reacts with SCN- to produce FeSCN2+ in water. For this reaction, A is the iron(III) ion, B is the thiocyanate ion, and C is the iron thiocyanato(III). Its Keq value is equal to K=([Fe(SCN)^(2-)])/([Fe^(3+) ][SCN^-]) and this can now be used to find the equilibrium constant with known or calculated concentrations. Methods; Standard curve; Five clean and dry test tubes are obtained and labeled 1-5. Each is filled with exactly 2.50 ml of 0.200 M Fe(NO3)3 using a burette. Next, 0.50 ml of 0.002 M KSCN solution is added to test tube 1. 0.75 ml of 0.00200 M KSCN is added to test tube 2 and so on in 0.25 ml increments. Finally, enough 0.5 M HNO3 is added to each test tube so that the final volume equals 10.0 mL. Each test tube is mixed, then the contents of each are added to a cuvette and tested in a spectrophoto...... middle of paper ...... imary productivity across vast regions of the world ocean. Copper (Cu), on the other hand, is a common anthropogenic contaminant in estuarine and coastal oceans that can act as toxic to microorganisms at high concentrations. Organic complexation of dissolved iron and copper by largely uncharacterized natural ligands in seawater has been shown to be an integral part of the ocean biogeochemistry of these metals, governing aspects of their solubility, supply and distribution. bioavailability in the marine environment. Recent research projects in the Buck Lab have examined the distribution, sources, and sinks of natural iron- and copper-binding organic ligands in seawater, biological transformations of iron and copper species, and the influence of copper-binding ligands on copper bioavailability and toxicity. in contaminated coastal and estuarine environments.