Untitled Document (Soil Science Quiz) PDF

Question 1 0 / 2 pts The swelling/shrinking tendency of some silicate clay minerals is due primarily to ________. Correct Answer the movement of soil solution in and out of the interlayers of the crystal You Answered e...

Question 1 0 / 2 pts The swelling/shrinking tendency of some silicate clay minerals is due primarily to ________. Correct Answer the movement of soil solution in and out of the interlayers of the crystal You Answered expansion in the width of the interlayers due to movement of larger ions such as K+ the presence of cations attracted by the negative charges on the internal surfaces Question 2 0 / 2 pts A soil with a pH of 7 has a H+ ion concentration of 0.0000001 Correct Answer True You Answered False Question 3 2 / 2 pts If you were seeking a soil colloid with a low capacity to adsorb ions, but something that would provide a very stable base for a foundation, which of the following would you choose? montmorillonite Correct! kaolinite vermiculite Question 4 0 / 2 pts What happens to pH dependent charge as the pH of the soil decreases You Answered it increases Correct Answer it decreases nothing Question 5 0 / 2 pts 50 g of Ca2+ (m.w. =40g/mol) contains how many moles of positive charge? You Answered 1.7 mol  Correct Answer 2.5 mol 17 mol Question 6 2 / 2 pts 1 mole of Mg2+ contains how many Mg2+ ions? Correct! 6.02x1023 6.02x1046 12.04x1023 Question 7 2 / 2 pts You find that the CEC of a soil at pH 5.0 is 16 cmolc/kg and at pH 8.2 it is 16 cmolc/kg. What is the most likely reason for this lack of difference?  ionization of carboxyl and phenolic groups to release H+ ion increase in the pH-dependent charges on 2:1 type silicate clays Correct! Isomorphic substitution creating permanent charge in the clay micelle Question 8 2 / 2 pts Soils rich in which type of clay would provide the best fertility? kaolinite illite Correct! smectite Question 9 0 / 2 pts A poorly buffered soil will need _______lime to change the pH of a field compared to a well buffered one Correct Answer less You Answered more the same amount of Question 10 2 / 2 pts Given that you have 60 g of K+, how many cmolec are present (m.w. of K+ = 39g/mol, 100 cmolc = 1 molec) 40 cmolec Correct! 154 cmolec  205 cmolec Question 11 0 / 2 pts The electronegative charge on 2:1 type silicate clays is due primarily to ________. You Answered the preponderance of tetrahedral sheets compared to octahedral sheets Correct Answer isomorphic substitution of one metallic atom for another in the crystal structure of the clay extremely small size of the individual colloid particles Question 12 2 / 2 pts The negative charges associated with smetitic clay crystals are due mostly to ________.  isomorphous substitution of Si for Al in the tetrahedral sheet isomorphous substitution of Al for Si in the tetrahedral sheet Correct! isomorphous substitution of Mg for Al in the octahedral sheet Question 13 2 / 2 pts Given the information in the table, calculate the Base Saturation of this soil 1 Kg of soil contains 8 cmolec as Ca2+ 3 cmolec as Mg2+ 2 cmolec as K+ 2 cmolec as Al3+ 1 cmolec as H+ 76% Correct! 81% 84% Question 14 2 / 2 pts An alkaline soil contains 10% clay and 1.5% humus. If the pure clay has a CEC of 40 cmolc/kg and the humus 200 cmolc/kg, calculate the CEC/kg of the soil. Correct! 7 cmolc/kg 11 cmolc/kg 16 cmolc/kg Question 15 0 / 2 pts Building a foundation on a soil high in smectite clays is always a good idea You Answered True Correct Answer False Question 16 2 / 2 pts Which of the following is a characteristic of soil colloids? Correct! very small size low water holding capacity  structure containing C, H, O Question 17 0 / 2 pts Some soil colloids exhibit positive charges under highly acid conditions. To what are these charges likely due? Correct Answer protonation of some hydroxy groups by excess H+ ions the release of some OH- ions leaving an unsatisfied positive charge on the colloid You Answered substitution of lower valent atoms for higher valent atoms in the octahedral sheet Question 18 2 / 2 pts 1 mole of Al3+ contains how many moles of positive charge? Correct!  3 molc 15 molc 27 molc Question 19 2 / 2 pts Given a H+ ion concentration of 0.000000063, what is the pH of the soil Correct! 7.2 6.5 4.7 Question 20 2 / 2 pts How does the amount of lime needed to neutralize the residual acidity in a clay loam soil compare to that needed to neutralize the active acidity in that soil?  residual requires considerably less Correct! residual requires a lot more residual requires a little more Question 21 2 / 2 pts In what range of soil pH is phosphorus generally most available to plants? 3.5-4.5 4.5-5.5 Correct! 5.5-7.0 Question 22 2 / 2 pts Given the information in the table, calculate the CEC of this soil 1 Kg of soil contains 8 cmolec as Ca2+ 3 cmolec as Mg2+ 2 cmolec as K+ 2 cmolec as Al3+ 1 cmolec as H+ Correct! 16 20.5 12.5 Question 23 0 / 2 pts Al3+ is considered an acid cation because Correct Answer it hydolyzes water and complexes the OH- leaving the H+ You Answered it hydolyzes water and complexes the H+ leaving the OH- It has it's own acidic properties independent of H+ Question 24 0 / 2 pts Acid rain isn't likely to have a large effect on a well buffered soil Correct Answer True You Answered  False Question 25 2 / 2 pts Soil pH should be checked in a number of spots across a field to account for changes in field conditions. This is called Correct! spatial variation temporal variation variation in temperature Question 26 2 / 2 pts Secondary minerals are most prominent in the ________ fraction of soils. sand silt  Correct! clay Question 27 2 / 2 pts You are working with a soil colloid known to have a cation exchange capacity of about 100 cmolc/kg of clay and a tendency to swell when wetted. Which of the following is it most apt to be the dominant clay mineral in this soil? Correct! monmorillinite fine-grained mica kaolinite Question 28 2 / 2 pts Humus is like 2:1 type minerals in which one of the following characteristics  influence of isomorphous substitution structural framework of the particles Correct! capable of adsorbing cation Question 29 2 / 2 pts The cation exchange capacity of vermiculite increases if pH increases. True Correct! False Question 30 2 / 2 pts A soil with a high CEC is likely to be  poorly buffered Correct! highly buffered have no buffering Question 31 0 / 2 pts While 2:1 type clays have significant internal surfaces, their external surfaces are generally much more extensive. You Answered True Correct Answer False Question 32 2 / 2 pts Isomorphous substitution involves the substitution of a tetrahedral sheet for an octahedral sheet. True Correct! False Question 33 2 / 2 pts A octahedral sheet is characterized by a plane of aluminum atoms surrounded by oxygen and hydroxyl groups. Correct! True False Question 34 2 / 2 pts Isomorphous substitution involves the substitution of one ion for another based on size. Correct! True False Question 35 2 / 2 pts Farmers can significantly decrease the pH of their fields by Using a NH4+ based fertilizer Using an organic source of N fertilizer Correct! Both of the other answers Question 36 2 / 2 pts A sandy soil would likely need to be monitored for pH changes more often than a clayey soil because the sandy soil is highly buffered True Correct! False Question 37 2 / 2 pts A liming material has a CaCO3 equivalent of 0.90. Of this liming material, 60% passes through a 10-m sieve and 30% passes through a 50-m sieve. If 1.5 tons of 100% CaCO3 is recommended, how much of this other liming materials is needed. (Efficiencies: 50-m = 100%, 10-m = 50%) 6194 lbs Correct! 7,407 lbs 5,420 lbs Question 38 0 / 2 pts Because of the ________, soils developed in marine marshes can become extremely acid if drained for agriculture or used as topsoil. You Answered reduction of sulfates reduction of elemental sulfur Correct Answer oxidation of sulfides Question 39 0 / 2 pts Assume you want to grow azaleas (needs an acidic soil) in a soil with a pH of 6.0. the application of which of the following would be most appropriate to decrease the soil pH Correct Answer elemental sulfur  gypsum You Answered chicken manure Question 40 2 / 2 pts Other things being equal, a soil with 30% clay of the ________ type would be expected to have the greatest potassium -fixing capacity. crystalline iron oxide Correct! 2:1 1:1 Question 41 2 / 2 pts Find the amount of limestone (CaCO3 equivalent = 0.92) needed to neutralize the same amount of acidity as 2 tons of burned lime with a CaO equilvalent of 0.90. (M.W. CaCO3 = 100 g/mol, M.W. CaO = 56 g/mol) 4000 lbs 3898 lbs Correct! 7000 lbs Question 42 0 / 2 pts Under which of the following conditions would you favor a finely ground dolomitic limestone as your choice of a liming material? need to significantly reduce the exchangeable Al3+ level in the soil Correct Answer need to provide magnesium in addition to calcium You Answered  need for a rapid reaction with the soil Question 43 2 / 2 pts What is the Calcium Carbonate Equivalent of MgCO3 (M.W. MgCO3 =84.3 g/mol, M.W. CaCO3 = 100.0 g/mol)? Correct! 1.19 1.79 0.93 Question 44 2 / 2 pts Soil pH can vary with soil depth Correct! True  False Question 45 2 / 2 pts A soil with a CEC of ______ would likely be highly buffered Correct! 40 cmolc/kg 15 cmolc/kg 5 cmolc/kg Question 46 2 / 2 pts How effective is 100 kg of 95% pure CaO (CCE=1.786) when compared to 100% pure CaCO3? 100 kg of 95% pure CaO would neutralize the same amount of acidity as ________of 100% pure CaCO3. Correct!  169.6lb CaCO3 178.6lb CaCO3 0.96lb CaCO3 Question 47 2 / 2 pts If 60% of a liming material passes through a 50-mesh sieve and 97% passes through a 10-mesh sieve, what is the effectiveness of the lime based on size only Correct! There is 0.79lbs of reactive material/lb total lime There is 0.44lbs of reactive material/lb total lime There is 0.97lbs of reactive material/lb total lime Question 48 2 / 2 pts How far ahead of crop planting should you plan to add lime if you are rotating your crops Correct! Lime should be applied 6-12 months prior to planting the crop with the most sensitive pH requirments Lime should be applied 1-2 months prior to planting the crop with the most sensitive pH requirments Lime should be applied immediately after planting the crop with the most sensitive pH requirments Question 49 0 / 2 pts Which of the following liming situations would potentially lead to a soil pH that is higher than intended Correct Answer applying 4 tons of lime to sandy soil You Answered  applying 4 tons of lime to a clayey soil applying 2 tons of lime to a silty clay loam Question 50 0 / 2 pts What is the Calcium Carbonate Equilivalent of CaMg(CO3)2 (m.w. of CaMg(CO3)2 = 184g/mol, m.w. of CaCO3 = 100.0 g/mol) Correct Answer 1.087 You Answered 0.54 1.786