Answer to Question #74420 in General Chemistry for Russell Hobbs

Question

The rate of weathering reactions in the environment are influenced by a number of factors including the rate of mineral dissolution.


The dissolution rate of olivine (Mg1.6Fe0.4SiO4) is 1x 10-14 moles cm-2 s-1 at pH 7 and 25oC.


Atomic weights: Mg 24.31, Fe 55.85, Si 28.09, O 15.99


Molar volumes: Olivine 43.67 cm3 mol-1, Quartz 22.67 cm3 mol-1


a) Assuming mass is uniformly removed from one side of an exposed crystal over time, how many years would it take for an olivine cube 0.1 x 0.1 x 0.1 cm to dissolve under these conditions? (5 marks)


b) In the presence of organic ligands which chelate Mg removal, the dissolution rate is increased to 1x 10-12 moles cm-2 s-1. With these organic acids present how long would it take to dissolve the same crystal? (5 marks)


c) Quartz dissolves at a rate equal to 1x 10-18 moles cm-2 s-1. How long would a quartz crystal take to dissolve given the same conditions? (5 marks)

Answer 1

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