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Section B.3 Geology: Phases and Components
Subsection B.3.1 Activities
Definition B.3.1 .
In geology, a phase is any physically separable material in the system, such as various minerals or liquids.
A component is a chemical compound necessary to make up the phases; these are usually oxides such as Calcium Oxide (\({\rm CaO}\) ) or Silicon Dioxide (\({\rm SiO_2}\) ).
In a typical application, a geologist knows how to build each phase from the components, and is interested in determining reactions among the different phases.
Activity B.3.3 .
To study this vector space, each of the three components \(\vec c_1,\vec c_2,\vec c_3\) may be considered as the three components of a Euclidean vector.
\begin{equation*}
\vec{p}_1 = \left[\begin{array}{c} 3 \\ 1 \\ 2 \end{array}\right],
\vec{p}_2 = \left[\begin{array}{c} 1 \\ 1 \\ 1 \end{array}\right],
\vec{p}_3 = \left[\begin{array}{c} 1 \\ 0 \\ 1 \end{array}\right],
\vec{p}_4 = \left[\begin{array}{c} 1 \\ 1 \\ 2 \end{array}\right],
\vec{p}_5 = \left[\begin{array}{c} 2 \\ 1 \\ 2 \end{array}\right].
\end{equation*}
Determine if the set of phases is linearly dependent or linearly independent.
Activity B.3.4 .
Geologists are interested in knowing all the possible chemical reactions among the 5 phases:
\begin{equation*}
\vec{p}_1 = \mathrm{Ca_3MgSi_2O_8} = \left[\begin{array}{c} 3 \\ 1 \\ 2 \end{array}\right] \hspace{1em}
\vec{p}_2 = \mathrm{CaMgSiO_4} = \left[\begin{array}{c} 1 \\ 1 \\ 1 \end{array}\right] \hspace{1em}
\vec{p}_3 = \mathrm{CaSiO_3} = \left[\begin{array}{c} 1 \\ 0 \\ 1 \end{array}\right]
\end{equation*}
\begin{equation*}
\vec{p}_4 = \mathrm{CaMgSi_2O_6} = \left[\begin{array}{c} 1 \\ 1 \\ 2 \end{array}\right] \hspace{1em}
\vec{p}_5 = \mathrm{Ca_2MgSi_2O_7} = \left[\begin{array}{c} 2 \\ 1 \\ 2 \end{array}\right].
\end{equation*}
That is, they want to find numbers \(x_1,x_2,x_3,x_4,x_5\) such that
\begin{equation*}
x_1\vec{p}_1+x_2\vec{p}_2+x_3\vec{p}_3+x_4\vec{p}_4+x_5\vec{p}_5 = 0.
\end{equation*}
(a) Set up a system of equations equivalent to this vector equation.
(b) Find a basis for its solution space.
(c) Interpret each basis vector as a vector equation and a chemical equation.
Activity B.3.5 .
We found two basis vectors \(\left[\begin{array}{c} 1 \\ -2 \\ -2 \\ 1 \\ 0 \end{array}\right]\) and \(\left[\begin{array}{c} 0 \\ -1 \\ -1 \\ 0 \\ 1 \end{array}\right]\text{,}\) corresponding to the vector and chemical equations
\begin{align*}
2\vec{p}_2 + 2 \vec{p}_3 &= \vec{p}_1 + \vec{p}_4 & 2{\rm CaMgSiO_4}+2{\rm CaSiO_3}&={\rm Ca_3MgSi_2O_8}+{\rm CaMgSi_2O_6}\\
\vec{p}_2 +\vec{p}_3 &= \vec{p}_5 & {\rm CaMgSiO_4} + {\rm CaSiO_3} &= {\rm Ca_2MgSi_2O_7}
\end{align*}
Combine the basis vectors to produce a chemical equation among the five phases that does not involve \(\vec{p}_2 = {\rm CaMgSiO_4}\text{.}\)
