“Soon after the city began supplying residents with Flint River water in April 2014, residents started complaining that the water from their taps looked, smelled, and tasted foul. Despite protests by residents lugging jugs of discoloured water, officials maintained that the water was safe. A study conducted the following year by researchers at Virginia Tech revealed the problem: Water samples collected from 252 homes through a resident-organized effort indicated citywide lead levels had spiked, with nearly 17% of samples registering above the federal “action level”. More than 40% measured above 5 ppb of lead, which the researchers considered an indication of a “very serious” problem.” Lead (Pb) was released from the distribution pipeline in the city of Flint due to a switch of the water source. (1) Please use Gibb’s formation energy in the table to find out the equilibrium constants for each reaction (R1-R4). (2) What will be total dissolved lead at pH 8 in pure water with the presence of Pd(OH)2(s)? What is the dominant species of dissolved lead? (3) If the alkalinity of this water (pH 8) is 20 meq/L, considering carbonate species are the only ones that contribute to alkalinity, will PdCO3 form?
Flint water crisis:
“Soon after the city began supplying residents with Flint River water in April 2014, residents started complaining that the water from their taps looked, smelled, and tasted foul. Despite protests by residents lugging jugs of discoloured water, officials maintained that the water was safe. A study conducted the following year by researchers at Virginia Tech revealed the problem: Water samples collected from 252 homes through a resident-organized effort indicated citywide lead levels had spiked, with nearly 17% of samples registering above the federal “action level”. More than 40% measured above 5 ppb of lead, which the researchers considered an indication of a “very serious” problem.”
Lead (Pb) was released from the distribution pipeline in the city of Flint due to a switch of the water source.
(1) Please use Gibb’s formation energy in the table to find out the equilibrium constants for each reaction (R1-R4).
(2) What will be total dissolved lead at pH 8 in pure water with the presence of Pd(OH)2(s)? What is the dominant species of dissolved lead?
(3) If the alkalinity of this water (pH 8) is 20 meq/L, considering carbonate species are the only ones that contribute to alkalinity, will PdCO3 form?
(4) If the water contains 10 mM chloride, what will be the new total dissolved lead?
(5) Some of the lead in the pipe was exposed to water containing dissolved oxygen. Please balance the reaction of R6. Considering the pe0 of Pd2+/Pd0 and O2/H2O are -2.13 and 14.5, respectively, will the oxidation of Pd0 by oxygen occur under conditions: pH 8, [Pd2+] = 5x10-8 M, [O2(aq)] = 2.5x10-4 M?
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