1. What are the most abundant elements in the Earth's crust and most soils?

2. What is the difference between chemical and physical weathering?

3. What are the 4 general types of colloids found in soils and what are their general characteristics?

4. What colloids dominate the clay fraction of soils representing an early stage of development? An intermediate stage? An advanced stage?

5. Sketch the structure of a 1:1 and 2:1 layer silicates.

6. Describe the 2 sources of charge associated with colloid surfaces.

7. What is the cation exchange capacity (CEC) of a soil? What factors affect it?

8. The A horizon of a local soil contains 4% organic matter and 20% clay. Assuming the soil has a pH of 7 and the clay fraction is made up of equal parts mica and vermiculite, estimate the CEC.

9. The A horizon of an Oxisol from the Amazon Basin of Brazil has the following properties: pH = 4; 2% organic matter; and 60% clay. Estimate the CEC.

10. What is a mole of charge? What is a cmol of charge?

11. How many cmol of Al³⁺ can be adsorbed on a soil with a CEC of 30 cmol_c/kg? Ca²⁺? K⁺?

12. Five cmol_c/kg of Ca are adsorbed to the colloidal surfaces of a soil. How many grams of Ca is this? How many pounds of Ca per acre furrow slice? How many cmol_c/kg of K would it take to replace this Ca? How many grams of K?

13. Define pH and describe how the pH scale is set up. If the H⁺ concentration (activity) of a soil solution is 0.000025 g/L, what is the pH?

14. What is the common range of soil pH values?

15. How does exchangeable Al³⁺ contribute to soil acidity?

16. What is the relationship between base saturation and pH?

17. With respect to pH, what is meant by a soil's buffering capacity? What is the general relationship between buffering capacity and CEC?

18. Distinguish between a saline soil, a sodic soil, and a saline-sodic soil.

19. Why do saline soils limit the growth and function of many plants?

20. Why do sodic soils limit the growth of many plants?