Final Exam Study Guide Flashcards
Name the soil horizons in order
O, A, E, B, C, R
Which horizon contains the most organic material?
O horizon
What does the O horizon contain?
Organic material; specifically fresh and decaying plants
What does the A horizon contain?
surface soil (top soil); mostly mineral material, still rich in organic matter (humus), has high biological productivity
What does the E horizon contain and what is it?
Eluviated- zone of leaching;
-Contains soluble minerals leached, leaving primarily sand and silt sized silicates, often bleached
-found in older, well developed soils
What is the B horizon and what does it contain?
Subsoil-zone of accumulation
-depleted in organic matter, new organic materials precipitated from leaching
What is the C horizon and what does it contain?
Substratum
-contains parent material, weathered and broken bedrock or deposits (like glacial till, loess, mass movement debris)
What is the R horizon and what does it contain?
Bedrock
-contains unweathered rocks
What is the regolith?
soil area containing all horizons except the R horizon which contains bedrock
-does not count as soil bc it has no organic material
What is leaching?
loss of water soluble materials and nutrients from the upper portion of the soil profile
-dissolution of soluble minerals or material going into suspension
What is elluviation?
removal of dissolved or suspended material from a layer/s of soil when precipitation is greater than evaporation
-materials move downward in the soil due to gravity
-is leaching materials
What is illuviation?
introduction of minerals (salts) or nutrients into a soil horizon leached from a previous soil horizon
What is humification?
breakdown of organic matter
What is bioturbation?
disturbance and transport of sediment and pore water by organisms as they pass through soils they mix the soil and help oxygenate it
5 soil factors that control soil formation
CLORPT
-climate
-organisms
-relief
-parent material
-time
What is Cl in clorpt?
-climate-temp speeds up or slows down chemical reactions that break down/weather rocks and minerals in areas of high rainfall, more water drains down, leaching materials through the soil horizons
What is Or in clorpt?
organisms: burrowing animals, growing plant roots, and enzyme-secreting bacteria and fungi chemically alter and physically mix soil
What is R in clorpt?
-relief-slope and direction a landscape faces-influenced by sunlight hours, temperature, runoff, erosion and organic matter build-up
What is p in clorpt?
parent material: chemical composition of original unweathered rock influences the mineral content of the soil; parent materials can be underlying bedrock but most are sediments like sand, silt or clay carried elsewhere by wind or water
What is t in clorpt?
time: weathering partly depends on age: older soils are more weathered than younger ones; soils in the tropics tend to be old because they have not been affected by the remixing effects of glaciation
What is molarity?
concentration of a solution expressed in moles/L
Molarity=moles of solute/L of solution
What is molality?
a measure of solute concentration in a solution
m= moles of solute/kg of solvent
What is a reversible chemical reaction?
a reaction in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously
Are the rates in the two directions of the reversible chemical reaction the same or different when a reversible reaction is at equilibrium?
Law of mass action: the speed of the reaction is proportional to the concentration of the reactants; eventually you hit dynamic equilibrium when the speed of each reaction is the same
what is the solubility product?(define and give value)
a substance’s solubility, Ksp (a slightly soluble salt)
-an equilibrium constant that describes the degree to which a solid substance dissolves in an aqueous solution
-the more soluble a substance is, the higher the Ksp value will be
What is K?
the equilibrium constant
solubility reaction equation
K= concentration of products/concentrationof reactants
-In equilibrium studies, the value of the concentration of
a pure liquid or solid is defined as 1
what is the pH equation?
pH= -log (H+)
what is the pOH equation
pOH= -log (OH-)
How is pH related to the concentration of dissolved hydrogen?
pH value is the logarithmic value of the inverse of the hydrogen ion activity. Since the concentration of hydrogen ions is often low ion activity is considered as equal to the concentration of hydrogen ions
What is chemical activity?(definition and equation)
a=ym (a=chemical activity; y=activity coefficient; m=molal concentration)
-is a measure of the effective concentration of a species in a mixture, which takes into account the interactions between the molecules in the mixture
-used to calculate the chemical potential of an ideal solution
-dependent on temperature, pressure, and composition of the mixture
Under what conditions do we need to use chemical activity instead of concentration and why?
When electrostatic forces cause the behavior of the solutes to be nonideal
How do you calculate ionic strength in a mixture of electrolytes in solution?
I= 1/2 sum(miX zi)
I= ionic strength
mi= molality of the ith ion
zi= charge of the ith ion