sw27 - Soil Organic Matter and Reactivity Acids give up...

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Unformatted text preview: Soil Organic Matter and Reactivity Acids give up hydrogen ions (H + ) to water. HCl H + + Cl-Strong acids give up all their H + ions Weak acids give up some of their H + ions CH 3 COOH CH 3 COOH CH 3 COOH CH 3 COO-CH 3 COO-H H Weak Acid (partial dissociation) HCl H H H H Cl Cl Cl Cl Strong Acid (complete dissociation) Weak Acid Dissociation is Strongly Dependent on the Amounts of the Products Already in Solution CH 3 COOH CH 3 COO-+ H + (Products) High amounts of acetate or H already The amount of H + in solution is pivotal High H + concentrations in solution inhibit dissociation Acetic acid acetate Hydrogen ion Charge on organic colloids is generated by dissociation of hydrogen ions from acidic functional groups, -OH and -COOH COOH COO-+ H + Soil Solution The functional groups on organic colloids are weak acids. COOH COO-+ H + OH O-+ H + Soil Solution They will partially dissociate COOH COO-+ H + OH O-+ H + Soil Solution The amount of dissociation is strongly dependent on the amount of H + in soil solution, or the pH Low pH, high amount of H in solution, poor dissociation High pH, low amount of H in solution, good dissociation COOH COO-+ H + Dissociation of weak acid functional groups results in the development of negative charge The amount of negative charge depends on how much dissociation takes place Low pH, little dissociation, little negative charge development High pH, much dissociation, abundant negative charge development Cation Adsorption Cation Adsorption COOH COO-+ H + COO-+ K + COO---K Adsorbed cation COOH O-K + K + COO-COO-COO-COO-OH O-O-O-COOH K + K + Ca 2+ Na + K + Na + Na + Mg 2+ Mg 2+ Mg 2+ Mg 2+ Na + Na + Na + Soil Solution...
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This note was uploaded on 02/04/2011 for the course SWS 3022 taught by Professor Bonczek during the Spring '11 term at University of Florida.

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sw27 - Soil Organic Matter and Reactivity Acids give up...

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