Environmental Chemistry 4

Which process does NOT affect the composition of water?

• Ion exchange

• Recombination

• Dissolution

• Hydrothermal activity

How does weathering change the composition of water?

• Through breaking of rocks

• Through evaporation

• Through deposition

• Through decomposition of organic matter

When a lake has a long retention time, it___

I.          Does not flush very often

II.          It has large volume

III.         It has high outflow

                        IV.          It allows pollutants to accumulate

• I, II, III

• I, II, IV

• II, III, IV

• I, II, III, IV

Identify a feature of epilimnion.

• Temperature decreases sharply

• Water is more dense

• Minor mixing occurs

• It is a transition zone

Choose a statement that best describes humic substances.

• It causes lakes to be eutrophic

• It increases the sediment in a river

• It can biodegrade quickly

• It slows down internal production

What happens when a lake becomes hypereutrophic?

• Hypolimnion has high dissolved oxygen

• Heavy metals are released from sediments

• Water has low phosphorus and chlorophyll

• Turbidity of water decreases

A gas with high solubility usually has

• High vapor pressure

• Low Henry's constant

• High polarity

• Low reaction with water

The mole fraction of nitrogen in the air is 0.78. What is the mole fraction of nitrogen in water?

• 9.12 x 10^-6

• 4.91 x 10^-6

• 2.46 x 10^-6

• 1.85 x 10^-5

Identify the CORRECT statements about dissolved oxygen (DO) in water

                            I.          At low pressure, the change of DO solubility with temperature decreases

                          II.          At higher dissolved salt content, DO becomes more soluble

                         III.          At higher temperature, DO becomes more volatile

                        IV.          At higher temperature, the change of DO solubility with pressure increases

• I, II

• I, III

• II, IV

• III, IV

O₂ makes up 21% of the air. What is the equilibrium concentration of O₂ in water?

• 0.273 mol/L

• 0.000491 mol/L

• 8.367 mg/L

• 8.736 ppm