lect 7 Flashcards
what does carbon dioxide do in water?
what is the water acidity and carbon dioxide in water?
strong acids such as HCl contribute to free mineral acid, a pollutant:
what is the speciation graph of CO2 in water?
CO32- has the greatest solubility in water due to polarity and charge
how much of CO2 turns into H2CO3 in water?
from air and as decomposition product of organic matter decay
-in water mainly as CO2(aq)
-relatively little as H2CO3 (<1%)
what does the acid-base equilibria look like for carbon dioxide species?
what is the slight acidity of unpolluted water?
homework example:
how to find the fraction of species (alpha) of CO2 in water?
what is alkalinity?
the capacity to accept protons (H+ ion)
homework example: the alkalinity of a river was determined to be 5 + 10^-3 mole H+/L and its pH is 8.0. Calculate the concentrations of CO3^2- and HCO3- and in the river
what is calcium and other metal ions in water?
what is the graph of carbon dioxide-calcium carbonate equilibria?
how do we determine the concentration of O2?
-titration by Winkler’s method
-spectrophotometry of oxidized dyes
-electrochemically by makareth O2 electrode
what is the titration by winkler’s method?
-treat water with manganese sulphate in alkaline solution
-manganese (Mn 4+) oxide precipitates
-manganese oxide the oxidizers I- to I2: titrate I2 with thiosulfate in the presence of a starch indicator
what is the spectrophotometric determination?
-dyes are oxidized by O2 in aqueous solutions
-color changes upon oxidation
-determine concentration by absorption of specific wavelength of light
-ex: pale yellow carmine forms indigo carmine upon oxidation
what is the electrochemical determination method (makareth O2 electrode)?
-O2 electrochemically reduced
-measure current flow at constant voltage
what is the anode and the cathode in the makareth O2 electrode method?
