(b) For many complex reactions in natural systems, reaction rates are approximat
ID: 554046 • Letter: #
Question
(b) For many complex reactions in natural systems, reaction rates are approximated by a fitting an overall reaction and determining a "pseudo-order" rate expression and rate constant. This treats an overall reaction mathematically the same as an elementary reaction, even though the reaction mechanism does not necessarily apply at the molecular scale. For example, the overall 3+ Fe2+ + 0.2502(aq) + H+ = Fe3+ + 0.5H2O At low pH, the rate of oxidation is observed to be independent of pH, but this reaction can be slow unless oxidation by O2 is catalyzed by bacteria. Write a rate expression for Fe oxidation at low pH that has a pseudo-first order dependence on the concentration of 02. Briefly explain your expression.Explanation / Answer
Pseudo first order reactions are those reactions which are high order reactions in actual but under certain condition i.e by changing the concentration of reactants, it behaves as first order reaction.
In present case there are three reactants Fe2+ , O2 and H+ , at low pH concentration of H+ ions is high so it nearly remains constant so rate of reaction becomes independent of it. We have to consider the dependence of O2 in present case , so we have to take Fe2+ in excess at low pH so that rate of reaction only depends on concentration of O2. Rate expression is given by :
Rate = k [O2]
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.