Unit 4 - Practice Quiz

1 Soil colloids are generally defined by particle sizes smaller than which of the following?

2 Which of the following is not a general property of soil colloids?

3 The fundamental building block of silicate clays consisting of one silicon atom surrounded by four oxygen atoms is known as a:

4 Which clay mineral typically has a 1:1 crystal structure?

5 In a 2:1 type silicate clay, the structure consists of:

6 Which phenomenon is primarily responsible for the permanent negative charge found in 2:1 silicate clays?

7 Which of the following clay minerals has the highest Cation Exchange Capacity (CEC)?

8 Illite is a non-expanding 2:1 clay primarily because of the fixation of which ion in the interlayer space?

9 Which group of soil colloids is amorphous (non-crystalline) and typically found in soils derived from volcanic ash?

10 What is the primary source of charge on humus (organic colloids)?

11 Under highly acidic conditions, the edges of Kaolinite may develop a positive charge due to:

12 The Cation Exchange Capacity (CEC) is commonly expressed in which units?

13 Which of the following sequences represents the correct order of adsorption strength (Lyotropic series) for cations on clay surfaces?

14 The specific surface area of Montmorillonite (Smectite) is significantly higher than Kaolinite because:

15 Which organic matter fraction is soluble in alkali but precipitates when the solution is acidified?

16 The 'Van Bemmelen factor' used to estimate Soil Organic Matter (SOM) from Soil Organic Carbon (SOC) is approximately:

17 A soil C:N ratio of 50:1 would likely result in which process?

18 Which component of plant residues is most resistant to decomposition?

19 The process by which individual clay particles stick together to form flake-like aggregates is called:

20 Which cation is the most effective dispersing agent, often leading to poor soil structure?

21 Sesquioxides are soil colloids dominated by:

22 Chlorite is structurally similar to vermiculite but contains an additional sheet in the interlayer space composed of:

23 The Point of Zero Charge (PZC) is the pH at which:

24 Which fraction of humic substances is soluble in both acid and alkali?

25 In the octahedral sheet of silicate clays, the central cation is typically:

26 Which of the following is true regarding the swelling/shrinking capacity of Kaolinite?

27 The breakdown of organic nitrogen compounds into ammonium () is specifically called:

28 Which soil colloid typically exhibits the highest specific surface area?

29 Anion Exchange Capacity (AEC) is most likely to be significant in:

30 The ratio of Silicon to Oxygen in a silica tetrahedron is:

31 Which of the following is a crystalline Iron oxide mineral?

32 The term 'isomorphous substitution' in tetrahedrons usually involves the substitution of:

33 Which of the following represents the correct C:N ratio range where neither net mineralization nor net immobilization occurs (equilibrium)?

34 Humus enhances soil physical properties primarily by:

35 The bonding force holding layers of Montmorillonite together is:

36 Which term describes the process where metal ions are bonded to organic molecules forming a ring structure, increasing metal solubility or availability?

37 Base Saturation is defined as:

38 The 'Diffuse Double Layer' theory explains:

39 Gibbsite is an example of:

40 Which of the following organic compounds decomposes most rapidly in soil?

41 The interlayer spacing (c-spacing) of expanded Montmorillonite with water can reach up to:

42 Which clay mineral is most commonly associated with 'cracking' soils (Vertisols)?

43 In the context of soil organic matter, 'Active Carbon' refers to:

44 What is the primary effect of high sodium saturation on soil colloids?

45 The net charge of 1:1 clays like Kaolinite is primarily:

46 Vermiculite differs primarily from smectite by having:

47 Which functional group is most responsible for the acidity of soil organic matter?

48 Colloidal particles in suspension exhibiting random, rapid zigzag motion is a phenomenon known as:

49 The total surface area of a soil is dominated by:

50 In the weathering sequence of clay minerals, which is considered the most weathered (end product)?