* not completed

. Which one(s) of the following statements is/are true? (Please select all that apply)

A colloid in a solution whose pH is greater than the colloidal pH_o will have a positive charge. correct incorrect

0.45 μm defines an operational size distinction between soluble and insoluble species correct incorrect

The Freundlich adsorption model assumes that adsorption is limited to monolayer coverage correct incorrect

The Langmuir adsorption model assumes that all adsorption sites are equivalent correct incorrect

Only colloidal sized material can be involved in adsorption correct incorrect

* not completed

. Which one(s) of the following statements is/are true? (Please select all that apply)

The relation C_s  =  K_d C_aq is a simplified version of the Freundlich relation that applies in many cases correct incorrect

In most cases, there is only weak binding between small organic species and mineral components of sediments or soils correct incorrect

The solvent n-octanol has the ability to associate with both polar and non-polar compounds correct incorrect

K_ow values can cover a range of greater than 10 orders of magnitude correct incorrect

The Langmuir adsorption process assumes a limited number of binding sites correct incorrect

* not completed

. Which one(s) of the following statements is/are true? (Please select all that apply)

K_ow describes the distribution of small organic molecules between octanol and water correct incorrect

K_om describes the distribution of small organic molecules between the organic fraction of solids and water correct incorrect

K_d describes the distribution of small organic molecules between the mineral fraction of solids and water correct incorrect

K_ow can be mathematically related to both K_om and the BCF correct incorrect

Octanol was chosen as the organic solvent due to its amphiphilic character correct incorrect

* not completed

. Which one(s) of the following statements regarding K_ow values is/are true? (Please select all that apply)

The units of K_ow are mol L^-1_w mol^-1L_o correct incorrect

Smaller K_ow values are characteristic of low molar mass organic species correct incorrect

Adding oxygen to aliphatic hydrocarbons will increase the K_ow correct incorrect

Polychlorinated biphenyls (PCBs) tend to have large values of K_ow correct incorrect

Large ratios of carbon to oxygen in an organic molecule tend to lead to large K_ow values correct incorrect

* not completed

. Estimate the average CEC value for the following sediment: 3% organic matter, 32% clay minerals; clay is one quarter montmorillonite and three quarters vermiculite.

  55 cmol (+) kg^-1 correct incorrect

214 cmol (+) kg^-1 correct incorrect

109 cmol (+) kg^-1 correct incorrect

  44 cmol (+) kg^-1 correct incorrect

  92 cmol (+) kg^-1 correct incorrect

* not completed

. Which of the following statements is/are true regarding quantitative measures of adsorption? (Please select all that apply)

The Langmuir relation assumes monolayer coverage of the adsorbate correct incorrect

The Langmuir binding constant (b) depends on the concentration of surface sites correct incorrect

Adsorption according to the Langmuir relation becomes more difficult as sites are filled correct incorrect

According to the general Freundlich relation, a plot of quantity of sorbate adsorbed (C_s) per mass of solid vs. its equilibrium solution concentration (C_aq) will be linear correct incorrect

The units of the Freundlich constant are L g^-1 correct incorrect

* not completed

. Which of the following statements regarding clay minerals is/are true? (Please select all that apply)

2:1:1 clay minerals are a class where two silica tetrahedral sheet are sandwiched between a pair of aluminium octahedral sheets correct incorrect

In a 1:1 clay mineral, the dissociation of –OH groups in the aluminium octahedral sheet is pH dependent correct incorrect

The substitution of aluminium for silicon in the tetrahedral layer produces a net negative charge correct incorrect

A large interlayer spacing between the layers favours exchange by cations correct incorrect

2:1 clay minerals generally have a greater CEC than 1:1 clay minerals correct incorrect

* not completed

. Which of the following statements about colloids in the environment is/are true? (Please select all that apply)

Iron and manganese oxides colloids present in water bodies may be made soluble under reducing conditions correct incorrect

At night, in a water body where photosynthesis is occurring, the pH declines slightly correct incorrect

Humic acid can be precipitated from water under acidic conditions correct incorrect

Photosynthesis can lead to the precipitation of CaCO₃ in a water body correct incorrect

Sulfides of some metals precipitate from solution in a low pE environment correct incorrect

* not completed

. Which of the following statements about phosphorus in the environment is/are true? (Please select all that apply)

PH₃ is commonly found in low concentrations in the atmosphere correct incorrect

Phosphorus, along with nitrogen and potassium, contributes significantly to eutrophication of water bodies correct incorrect

Phosphorus-containing minerals in soils are readily solubilized and leached into surface and ground water correct incorrect

Phosphorus compounds are added to detergents because of their surface active properties correct incorrect

It is easier to manage diffuse sources of phosphorus rather than point sources in terms of preventing eutrophication correct incorrect

* not completed

. Which of the following statements about clay minerals is/are true? (Please select all that apply)

Clay minerals are products of the weathering of primary minerals correct incorrect

A 2:1 sheet in a clay mineral consists of silicon tetrahedral sheet sandwiched between two aluminium octahedral sheets correct incorrect

A small amount of the negative charge of a 1:1 clay mineral is pH dependent correct incorrect

A large amount of charge in a 2:1 clay mineral is associated with silicon substituting for aluminium in the octahedral layer correct incorrect

The CEC of clay minerals depends on the particle size of the mineral correct incorrect