THEORY EXPERIMENT 4 DETERMINATION OF AN EQUILIBRIUM CONSTANT BY OBJECTIVES (1.) To gain experience with the important method of visible spectrophotometry; and (2.) use this technique to determine the equilibrium constant for the formation of the complex FeSSA(aq) from Fe³+(aq) and H₂SSA (aq). All chemical reactions move spontaneously towards an equilibrium state when the reactants are mixed in arbitrary concentrations. The equilibrium state for a given temperature and pressure is reached when the concentrations of reactants and products are no longer changing. However, when the system approaches and then attains the equilibrium state, there are two opposite processes taking place: the reactant molecules are reacting to form products, and the product molecules are reacting in the reverse direction to form reactant molecules. At the final equilibrium state, the forward and reverse reactions are taking place at the same rate, so that there is no net change in the concentrations of the products and reactants. Mathematically, when the system reaches equilibrium, the product of the molarities of the products raised to their stoichiometric coefficients divided by the product of the molarities of the reactants raised to their stoichiometric coefficients is equal to a constant, called the equilibrium constant, Keq,. As a general example, consider the reaction: aA(aq) +bB(aq) cC(aq) + dD(aq) Q- SPECTROPHOTOMETRY where A (aq) and B(aq) are reactants, C(aq) and D(aq) are product species, and a,b,c, and d are their respective stoichiometric coefficients in the balanced equation. Away from equilibrium, the reaction quotient Q is defined as: [C][D]* [A][B] = [C], [D] [A][B] (1) where the brackets represent the molarity of a species. As the system approaches equilibrium, Q→Keq, and at equilibrium Q=Keq, Ka (2) where the subscripts eq signify the final equilibrium molarities of each species. Keq has a fixed value for any given temperature and pressure, but is independent of the molarity of the species present at equilibrium.

LIMIT TEST (IMPURITIES - BIOLOGICAL) Instructions: Note the color change of each of the samples by writing blue or pink accordingly. Then give inference whether the sample is contaminated or not contaminated upon observation. Answer the highlighted numbers.     BLANK  (Sterile distilled water) Reference Sugar Solution Sample A Sample B REPLICATE 1 BLUE BLUE PINK PINK REPLICATE 2 BLUE PINK BLUE PINK REPLICATE 3 BLUE PINK PINK PINK INFERENCE NOT CONTAMINATED CONTAMINATED 1 2   1. 2. 3. Which of the two samples is relatively clean of biological impurities? 4. Given the result in limit test as an analyst, what will be the final conclusion to this? Write whether rejected or accepted for each sample.  (see attached photo)

H2, Ni +zog'20

Everything is in the photo. I need A through E. Plus the sentence at the top of the paper.