Please answer all parts, is all one question.

Assuming that layer silicates and humic acid exist independently in the soil, calculate a typical CEC that would be measured for a soil at pH 7 containing

Example to answer the next parts for the same question:

CECsoil= (Fclay * CECclay) + (Forganic matter * CECorganic matter)= ((300g/1000g)(1mol*kg^-1))+((20g/1000g)(1.6mol*kg^-1))= 0.332mol/kg

(a) 270 g kg-1 montmorillonite and 25 g kg-1 SOM,

(b) 270 g kg-1 kaolinite and 25 g kg-1 SOM, and

(c) 160 g kg-1 kaolinite and 15 g kg- 1 SOM.

(d) Are these calculations realistic? Why or why not? (See Figure 3 for reasonable values of SOM charge at pH 7).

The CEC would be the sum of the structural (permanent) charge in the clay mineral plus that resulting from pH-dependent charge of the SOM.