1499. Category: Mathematical Calculation

A large part of geochemistry deals with the distribution of elements in the Earth, which is the function of the planet`s differentiation history and chemical properties of the elements. Being able to predict how well elements will substitute into minerals is thus a key aspect of geochemistry.

  1. Using Goldschmidt`s rules, predict whether Zr will substitute readily for Ti in the mineral rutile (TiO2)
Cation Ionic radius6-fold coordination(charge) Electronegativity
Si 0.48(4+) 1.8
Ti 0.94(2+),0.75(3+),0.69(4+) 1.5
Sr 0.98(2+) 1.0
Zr 0.80(4+) 1.4
Hf 0.79(4+) 1.3
U 1.23(3+),0.97(4+),0.84(5+),0.81(6+) 1.7

 

  1. What would you predict to be the relative D-values(partition coefficients) for the elements listed in table 1 for rutile? Frame your answer in the form of Dw>Dx~ Dy>Dz etc, where w, x, y and z are the different elements from the table (no need to include Ti).
1500. Category: Short answers

Discuss the behavior of the REE during mantle melting. What properties of the rare earth elements (REE) make them useful in geochemistry(think in terms of the Goldschmidt parameters of size and charge)

1501. Category: Short answers

How do the REE behave during the mantle melting? are they compatible, incompatible or do they show mixed behaviors depending on the elements considered>. Do the REE fractionate from one another during mantle melting?. If so, in what way?

1520. Category: Mathematical Calculation

Calculate the solubility of Pyrite(FeS2) in pure water at 25ºC . Express the solubility as mole per litre, gram per litre and as parts per million. The solubility product constant for the reaction is 10-44.4 . Molecular weight of Fe=56, S=32.

1521. Category: Short answers

You are given the following chemical reaction:

Fe(OH)_3+CH_4leftrightarrow CO_2+Fe^{2+}

Balance it and state if the reaction is a function of Eh, pH or both. Will increasing pH have an effect on the reaction? If so how?

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