Environmental Chemistry 04.04.17

Question 1

What is the right answer?

a) It is more likely to find Fe3+ dissolved in river waters than in underground waters.
b) It is more likely to find Fe2+ dissolved in river waters than in underground waters.
c) It is more likely to find Fe2+ at the surface of a lake that in its sediments.

Answer 1

a) It is more likely to find Fe3+ dissolved in river waters than in underground waters

Question 2

Which one of the following statements concerning the two inorganic species of nitrogen (NO3- and NH4+)
found in the hydrosphere is true?
a) The concentration of both NO3- and NH4+ in natural waters is always high.
b) The nitrate ion forms highly insoluble compounds that precipitate in sediments and soil.
c) The concentration of nitrate ion can be particularly high in underground water because soil particles cannot retain that ion.

Answer 2

c) The concentration of nitrate ion can be particularly high in underground water because soil particles cannot retain that ion.

Question 3

Eutrophized lake waters:

a) have a high oxygen content.
b) are anaerobic.
c) are more oxidizing that surface sea waters.

Answer 3

b) are anaerobic.

Question 4

Phenolphthaleinic alkalinity refers to the concentration of:

a) HO- and CO32-.
b) HO-.
c) HO-, CO32- and HCO3- .

Answer 4

a) HO- and CO32-.

Question 5

Which one of the following sentences is true?

a) A wastewater is more biodegradable when BOD and COD values are high.
b) A wastewater is more biodegradable when BOD and COD values are low.
c) A wastewater is more biodegradable the higher the BOD value and the lower the COD value.

Answer 5

c) A wastewater is more biodegradable the higher the BOD value and the lower the COD value.

Question 6

Which one of the following reactions is the responsible for the high Ca2+ content of natural continental waters?
a) CaCO3 + CO2 +H2O ⇌ Ca +2 + 2HCO3-

b) CaCO3 +Humus —>Ca+2 + Humus + CO3-2
c) Ca(OH )2 + 2HCl –> Ca+2 + 2Cl- + 2H2O

Answer 6

a) CaCO3 + CO2 +H2O ⇌ Ca +2 + 2HCO3-

Question 7

Which one of the following conditions is a valid reason for colloid flocculation in natural waters?

a) An increase of O2 content.
b) An increase of organic materials.
c) A conductivity increase.

Answer 7

c) A conductivity increase.

Question 8

Which one is the right statement?

a) Compounds that are more bioaccumulative normally have more acute toxicity.
b) BCF (Bioconcentration factor) values are always bigger than KOW values.
c) Bioaccumulation and Biomagnification are not the same concept.

Answer 8

c) Bioaccumulation and Biomagnification are not the same concept.

Question 9

Normally, the water of a continental lake can show stratification:

a) Only in summer.
b) In summer and winter if the surface temperature is near 0ºC.
c) All year.

Answer 9

b) In summer and winter if the surface temperature is near 0ºC.

Question 10

Let’s take into account the following water samples: marine sediment, Pyrenees river, atmospheric water, tropical river. What would be the most logical order of pe values (from high to low):

a) Atmospheric water > Pyrenees river > tropical river > marine sediment.
b) Atmospheric water > Pyrenees river ~ tropical river > marine sediment.
c) Atmospheric water > tropical river > Pyrenees river > marine sediment.

Answer 10

a) Atmospheric water > Pyrenees river > tropical river > marine sediment.

Question 11

The pH of surface sea water is 8,2 (slightly basic). What is the reason of that?

a) The presence of large amounts of hydroxides (Fe(HO)3, Al(HO)3, etc.) poured in the sea by continental rivers.
b) The sea is a medium where alkaline cations like Ca2+ and Mg2+ predominate.
c) The sea is a highly saline medium where the Ca2+/CO2/HCO3-/CaCO3 system is in equilibrium.

Answer 11

???

Question 12

Which one of the following compounds has a larger acute toxicity?

a) Dioxine.
b) Polychlorinated byphenil.
c) Polyaromatic hydrocarbon.

Answer 12

a) Dioxine.

not sure

Question 13

Which one of the following metal cations is a micronutrient?

a) Na+.
b) K+.
c) Zn2+.

Answer 13

c) Zn2+.

Question 14

What is the best combination of semidegradation time (t1/2) and soil/water distribution constant (KS,A)
values for an organic pollutant to leach to the aquifer?
a) Low t1/2 and low KS,A.
b) Low t1/2 and high KS,A.
c) High t1/2 and low KS,A.

Answer 14

c) High t1/2 and low KS,A.

Question 15

Municipal wastewaters are characterized by:

a) Presence of toxic substances.
b) High level of biodegradable organic pollution.
c) Low level of pollution.

Answer 15

b) High level of biodegradable organic pollution.

Question 16

Dichromate (Cr2O7-2) is used to determine:

a) the BOD (Biochemical Oxygen Demand).
b) the COD (Chemical Oxygen Demand).
c) the TOC (Total Organic Carbon).

Answer 16

b) the COD (Chemical Oxygen Demand).

Question 17

What kind of chemical process predominates at the bottom of a deep lake?

a) Photochemical reactions.
b) Anaerobic reactions.
c) Oxidation reactions.

Answer 17

b) Anaerobic reactions.

Question 18

With respect to fulvic acids humic acids:

a) have less organic acid groups.
b) are more soluble in water.
c) can interact with a larger amount of metallic cations.

Answer 18

a) have less organic acid groups.

Question 19

Which one of the following parameters has a relevant influence on the marine water density?

a) Temperature.
b) The concentration of colloids.
c) Dissolved oxygen.

Answer 19

a) Temperature.

Question 20

Attending to the pe values of the following aqueous redox systems at neutral pH:
1/4O2 + H+ + e- –> 1/2 H2O pe=13.75
1/2 Fe2O3(s) + 3H+ + e- –> Fe2+ + 3/2H2O pe=-9.8
1/2S(s) + H+ + e- –> 1/2H2S(g) pe=-4,11
which one is the right order of the oxidizing character of the redox species involved?
a) O2> S(S)>Fe2O3(S)
b) Fe2O3(S)>O2)> S(S)
c) H2O>Fe2+>H2S(g)

Answer 20

a) O2> S(S)>Fe2O3(S)

not sure

Question 21

What is the meaning of a water sample with a high biological oxygen demand (BOD) ?

a) The water sample has a high biological activity.
b) The water sample has a high oxygen content available for organic matter oxidation.
c) The water sample has a large content of biodegradable organic material.

Answer 21

a) The water sample has a high biological activity.

Question 22

In one of the continents 86% water consumption goes to agriculture, while industry takes 8%, and domestic consumption is 6%. What continent is that?

a) Asia.
b) Africa.
c) Europe.

Answer 22

a) Asia.

Question 23

Which one is the main drawback of the use of chlorination in drinking water treatment?

a) Generation of trihalomethanes.
b) Lack of residual disinfection power.
c) High price.

Answer 23

a) Generation of trihalomethanes.

Question 24

The Fenton reaction is used to destroy toxic or non biodegradable organic pollutants. Fenton reaction is:
a) Fe(III)+H O2 visible→Fe(II)+HO +H
b) Fe2+ +H2O2 →Fe3+ +OH• +OH−
c) TiO2 +HO +O2 −hν<380nm •−→TiO2 +HO +O2
see paper

Answer 24

b) Fe2+ +H2O2 →Fe3+ +OH• +OH−

Question 25

Which one of the following sentences is the correct one?

a) A transition metal ion with more methyl substituents has more solubility.
b) A transition metal ion with more methyl substituents forms an organometallic compound of lower molecular weight.
c) A transition metal ion with more methyl substituents is more volatile

Answer 25

Not sure