1. What would be the pH if 10 -2 moles of sulfuric acid (H 2 SO 4 ) were added t
ID: 845446 • Letter: 1
Question
1. What would be the pH if 10-2 moles of sulfuric acid (H2SO4) were added to 1 L of water. Sulfuric acid is a strong acid.
2. At a wastewater treatment plant, FeCl3(s) is added to remove excess phosphate from the treated effluent by forming solid FePO4(s) as shown in the following reactions:
FeCl3(s) = Fe3+ + 3Cl-
FePO4(s) = Fe3+ + PO43- Ksp= 10-26.4
What concentration of Fe3+is needed to maintain the phosphate concentration below the regulatory limit of 1 mg P/L.
3. A first-order reaction that results in the destruction of a pollutant has a rate constant of 0.1 day-1. (a) How many days will it take for 90% of the chemical to be destroyed? (b) How long will it take for 99% of the chemical to be destroyed? (c) How long will it take for 99.9% of the chemical to be destroyed? (d) What is the half-life of the pollutant?
Explanation / Answer
1
Molartity = number of moles/ volume of solution
=10^-2/1
=10^-2 M
[H+]=2*10^-2 M (because one H2SO4 gives 2 H+)
pH= -log [H+]
= -log(2*10^-2)
= 1.7
2
When zinc hydroxide precipitates, the ion concentrations satisfy equilibrium condition:
Ksp_Zn(OH)? = [Zn
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