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“Review of Chemical Principles and Clay Minerals” Due: September 16, 2004 |
| 1.) | a.) Place the following atoms in the order of increasing size: Br, F, Cl, Cs. | |
| b.) Place the following atoms in the order of decreasing electronegativity: F, O, N, C | ||
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2.)
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A recipe for preparing a soil extractant solution specifies
that you add 1.0 g of sodium dithionite (Na2S2O
4) to 200 mL of a solution of 0.2 M sodium citrate. Assuming
that the final volume remains 200 mL, what is the final molar concentration
of citrate, dithionite, and sodium
in this solution? (Atomic weight: Na, 22.9g mol-1; O, 16.0 g mol-1; S, 32.1 g mol-1) |
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3.)
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Find the pH value of the following solution
at 25 oC: 0.01 M sodium acetic acid if the pKa is 4.5.
Show the number of species in solution, the total number of independent
equations needed to solve for these unknowns, and the approximation equations
used. |
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4.)
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Given below the following pairs of cations and
anions, determine the radius sum in Å, radius ratio, coordination
number (CN), and geometrical (crystal) arrangement for each pair. Use the ionic radii values presented in Tables 2.3 of the text book .. |
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| a.)
Fe3+ and Cl- |
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| b.) Na+
and Cl- |
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| c.) Ca2+
and Cl- |
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| d.) Si4+
and Cl- |
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5.)
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You analyze the <2μm clay fraction of a soil from
Kentucky using x-ray diffraction. The d-spacings (001)
are given below. Identify the clay mineral suite and provide a rationale for the identification. |
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| K-saturation |
Mg-saturation |
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| T(K)
d-spacings (nm) |
T(K)
d-spacings (nm) |
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298
0.72, 1.0, 1.4 |
298
0.717, 1.0, 1.77 |
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383
0.73, 1.0, 1.38 |
383
0.72, 1.0, 1.4 |
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573
0.72, 1.0, 1.4 |
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| 823
1.0 |
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6.)
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One major mechanism of
N loss from soils is denitrification. Fit the data below using the
best-fit elementary
rate equation and estimate the rate coefficient and the time needed for 1/8 of the initial concentration of NO3- to be remaining. Would the t1/2 be affected if the initial NO3- concentration was doubled? |
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| Time (days) |
NO3-
(mg L-1) |
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| 0 |
240 |
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| 5 |
167 |
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| 10 |
125 |
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| 25 |
50 |
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| 40 |
20 |
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