Question

Contrast elementary and overall reactions with some examples. What is meant by the term 'rate-limiting step? Define a zero-, first- and second-order reaction and find an example of each for from the aqueous geochemistry world (text, web, etc). Using Excel, develop graphical representations of zero-, first (reactant)- and second-order (reactant^2) rate expressions showing: rate (y) vs. time (x) reactant cone. (y) vs. time (x) Discuss how these idealized plots might be used to interpret observed experimental rate data. Compare and contrast the Arrhenius and Van't Hoff Equations including the basis for the activation energy and enthalpy terms. The rate of a reaction doubles between 25 and 50 degrees C. What is the activation energy? What type of reaction might have an activation energy of this magnitude? Actual rates of mineral phase dissolution/weathering reactions are sensitive to surface area. In fact, the rate of dissolution (R) is proportional to the surface area to solution volume ratio (A/V). Assumptions: constant temperature, pressure, and solution chemistry. Calculate the A/V ratio for a stone monument exposed to acidic attack assuming the water flowing over the monument is 1 mm thick. Now recalculate the A/V ratio assuming a rock porosity of 18%, rock density of 2.7 g/cm^3 and internal rock surface area of 1 m^2/g. Assume all the porosity is occupied by water. Compare and discuss the results of both calculations

Answer 1