A simulation of the interaction of acid rain with soil minerals. 6

ABSTRACT : The environmental issue of acid rain is incorporated into a five-part laboratory project that employs quantitative analytical laboratory techniques, such as acid-base titrations and gravimetric analysis of aqueous cations. The student observes the effectiveness of soil at consuming excess acidity in rainwater and observes the mobilization of Al3+ and Ca2+ from these interactions. The first four parts of the project involve passing a sulfuric acid solution through a column containing aluminum hydroxide, limestone, montmorillonite clay, or synthetic zeolites (molecular sieves). After its passage through the column, the acid solution is analyzed by titration to determine the resulting acidity and by precipitation of the aqueous Al3+ or Ca2+ with 8-hydroxyquinoline. In the fifth part of the project, an aluminum sulfate solution is passed through a column containing molecular sieves to observe the absorption of Al3+ once it has been mobilized from minerals by acid rain. The five-part project can be treated as an individual student project to be completed during multiple consecutive lab sessions, or divided up as a group or class project that can be completed during one or two lab periods. 56

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