L.4 - Chemistry Flashcards
Define environmental chemistry:
It is the study of composition, reactions, and characteristics of matter
Why do we care to learn about envi. chemistry?
because it influences the ultimate fate of many chemicals discharged to soil, air, and water
What are the fundamental properties that the chemical basis depend on?
1) Air pollution
2) Water pollution
3) Sustainability
4) Climate change
5) Water quality management
6) Air quality management
7) Solid waste management
A chemical system is in equilibrium when:
1) at steady state (doesn’t vary with time)
2) it is well mixed
3) there is no net flow of mass, heat, or species w/ the surroundings
4) the net rate of chemical reaction is zero
What is pH?
-log [H+] (minus log of the hydrogen ion activity)
Define activity:
it is the measure of the effective concentration of a species in a mixture
When is pH acidic and when is it alkaline (w/ examples)?
pH = 7 neutral (ex. pure water) also where [H+]=[OH-]
pH < 7 acidic (ex. coffee, acid rain)
pH > 7 alkaline (ex. baking soda, bleach)
What does pH affect?
- solubility in metals
- corrosiveness in water
- other chemical reaction rates
Define molarity:
it is the number of moles of solvent dissolved in one litre of solution
What is the standard chemical reaction equation?
aA + bB <> cC + dD (reactants <> products)
(A,B,C,D: distinct molecular species)
(a,b,c,d: number of units of species participating in reaction)
What do these “[]” represent?
the activity of the species in mol/L (solid & water activity = 1)
What is the equilibrium constant for water at 25’C?
Kw=10^-14
What are some equilibrium constants used other than of water?
1) Air-Water: Henry’s constant “KH”
2) Acid-Base Chemistry: Acid Ka, Base Kb
3) Precipitation Dissolution: Solubility product “Ksp”
What is electroneutrality?
when the sum of cations = the sum of anions
[H+] = [OH-]
As temp. increases, pH…..?
decreases
In a solution who produces [H+] and who produces [OH-]?
acids produces [H+], base produces [OH-]
Wen is solid-liquid equilibrium reached?
when a solid dissolves into ionic compounds at the same rate that ionic components recombine into solid form
What does the degree of dissolution of air in water depend on?
- temperature
- water purity
- constituents present
Define Alkalinity:
the measure of water’s capacity to neutralize acids (by removing [H+] ions)
Define Buffering Capacity:
ability of water to resist changes in pH when either acidic or alkaline material is added
What is partitioning?
how much the dissolved contaminant will partition onto the soil grain (equal to the amount dissolved in water)
Define Adsorption:
when particles stick to the surface of the soil grain
Define Absorption:
when particles are absorbed into the soil grain
What is Organic Chemistry?
chemistry of compounds with carbon
