7) Intro to Water Chemistry

what are properties of water?

most important substance on planet, dipolemoment, polar bond and lone pairs on O atoms, high melting point and high boiling points

how can H bonds happen?

between H and a soluble molecule (both polar)

what is the crystal structure of water?

hexagonal

what is the angle between H-O-H?

105*

what is the difference between water crystal structure and H2S crystal structure?

water crystallizes with space in between (open), H2S crystallizes in closely packed arrangement (closed)

how does water interact with ions?

positive ions will have O surrounding them (partial negative), and negative ions will have H surrounding them (partial positive)

what are special properties of water?

high heat capacity, high dielectric constant, high surface tension, transparent to visible and UV light, dissociation constant

what is important about water’s heat capacity? what does it cause?

highest among all common liquids, temp stabilization in areas adjacent to large bodies of water

what is special about the open structure of ice? connection to environment?

low density, ice floats, ensuring survival of orgs in water in winter

at what temperature is water’s density the highest?

4*C

what is important about water’s dielectric constant? what does it cause?

highest of any common liquid, excellent solvent, mediates biochemical processes and transport of nutrients and waste pdts

what is important about water’s surface tension? importants?

high surface tension, bugs can walk on water, drop and surface phenomena on biomembranes

what is important about water’s transparency?

transparent to visible and UV light, allows light for photosyntehsis to penetrate water bodies to considerable depth

what is important about water’s dissociation constant?

the rate at which water turns into it’s positive and negative ions, kd=1.008×10^-14

what is info about hydrologic cycle?

earth’s surface covered 71% by water, cycle driven by the sun

where is most of the freshwater?

in polar ice caps and alpine glacier

what is the distb of water use?

69% agriculture, 23% industry/power, 8% domestic

what is desalination? extra?

removing salt from sea water, excess salt could be stored in underground salt mines

why is there no Fe2+ or Al3+ in rivers?

they react with O2 and form insoluble hydrosulfides

what are TDS? Info about them in rivers?

total dissolved solids, rivers with low TDS are likely flowing through granite, because it doesn’t give up its iron very easily

what was the manitoba lake experiment?

one side of lake introduced only N and C, on the other side, N, C, and P, side with phosphorous had sever algal bloom, killing all fish

explain the nutrient cycling diagram

C is usually plentiful, N is possibly limited, and P is usually limited, this means that an increase in P is much more valuable to algae, they will start multiplying intensely

why is C usually abundant?

atmosphere is in direct contact with water, CO2 can dissolve

why are H2O and H2S in different states at room temp?

water has H bonding, H2S does not, causes its low boiling point

what is important about dissolved gases? specifics?

critical for life, O2 for fish, CO2 for photosynthetic algae

what was lake nyos?

massive release of CO2 from deep below the water, underwater vents allowed Co2 to enter water body, cold rain cooled the surface water, increasing its density and forcing other water upwards

what are fish kills mostly caused by? misconception?

decrease in O2 and not toxic pollutants

is CO2 mostly present as H2CO3 in the water?

no, it’s mostly HCO3-

why is pure water slightly acidic?

CO2 is dissociated into H+ and HCO3-

at what pH will the conc of HCO3- be highest?

8.5

how does HCo3- act like a buffer?

it reacts with H+ (in acid rain) to form CO2 and H2O

explain the carbonate-bicarbonate system diagram

Co2 in air interacts with water surface, then dissolves into H2CO3, then dissociates into H+ and HCO3-. CaCO3 form rocks/sediemnts dissociates into Ca2+ and CO32-, then interact with H2O to form OH- and HCO3, then the H+ and OH- form both sides makes H2O

how can you figure out solubility?

by figuring out how many grams went into solution, using KL equation and concentrations

what does weathering require? what do they do?

formation of abiotic acids, which then react with minerals

what is saltiness?

amount of dissolved inorganic minerals

what is the reason for high levels of Cl in ocean?

volcanic eruptions spew Cl rich gas, same with deep sea vents for Ca and Mg

what is black smoke made of?

iron sulfide particles

why doesn’t salinity of ocean increase over time?

salts are continually removed by processes such as deposition on or within the seafloor, evaporation and sea floor