Group II/III: Pb2+ Cu2+ Bi3+ Sb3+ Cr3+ Mn2+ Fe3+ Ni2+ Zn2+ Co2+ Al3+Final REPORT: Lab Notebook pages only.
1) Notebook pages must have observations clearly stated and accompany the Flow Chart(s) 2) NIEs equations must be included for ALL reactions of the ions present in the unknown sample in the Results section.
3) Turn-in FormPost lab Reading & Questions: Iron Mountain, California
Iron Mountain Mine, also known as the Richmond Mine at Iron Mountain, is a mine near Redding in Northern California. Geologically classified as a "massive sulfide ore deposit", the site was mined for iron, silver, gold, copper, zinc, and pyrite intermittently from the 1860s until 1963. The mine is the source of extremely acidic mine drainage which also contains large amounts of zinc, copper and cadmium. One of America's most toxic waste sites, it has been listed as a federal Superfund site since 1983.
The drainage water from the Iron Mountain Mine is the most acidic water on Earth; some samples collected in 1990 and 1991 have been measured to have a pH value of -3.6, which is the lowest pH observed globally in an natural environment.
When pyrite is exposed to moisture and oxygen, sulfuric acid forms. This sulfuric acid runs through the mountain and leaches out copper, cadmium, zinc, and other heavy metals. This acid flows out of the seeps and portals of the mine. Much of the acidic mine drainage ultimately is channeled into the Spring Creek Reservoir by creeks surrounding the mine. The low pH level and the heavy metal contamination from the mine have caused the virtual elimination of aquatic life in sections of Slickrock Creek, Boulder Creek, and Spring Creek.
The mine was designated a Superfund site in 1983 and a water treatment plant was built in 1994. In 2000 the government reached a settlement with the responsible parties for the long-term funding of the cleanup efforts, which will require ~ 1 billion dollars.Acid mine drainage biogeochemistry at Iron Mountain, California
Gregory K Druschel, Brett J Baker, Thomas M Gihring, and Jillian F Banfield
Geochem Trans. 2004; 5(2): 13
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1475782/Post Lab Questions:Large natural deposits of iron pyrite, "fool's gold", which has the unusual molecular formula FeS2 is Fe2+S22-, where the sulfur is a diatomic anion with a covalent S–S bond. Therefore, pyrite is correctly named as iron (II) persulfide and not iron (II) sulfide as seen in some references.
Sulfuric acid is formed naturally by the oxidation of iron (II) persulfide. The resulting water is highly acidic and is called acid mine drainage (AMD) or acid rock drainage (ARD). This acidic water is capable of dissolving other metal minerals present in sulfide ores, which produces brightly colored (usually blood red), streams. They are acidic with high concentrations of metals that are toxic to fish and aquatic organisms. The oxidation of pyrite, iron (II) persulfide, with molecular oxygen produces iron(II), Fe2+, and sulfuric acid.1) Write a balanced Net Ionic Equation for the redox reaction:Fe2+ is further oxidized with oxygen to Fe3+ under acidic conditions
2) Write a balanced Net Ionic Equation for the redox reaction:The Fe3+ produced can be precipitated in water as the hydroxide.
3) Write a balanced Net Ionic Equation for the precipitation reaction:4) Write the equlibrium reaction and the solubility product expression for the solubility of iron(III) hydroxide:Iron(III) ion oxidizes pyrite in water to produce sulfuric acid and iron (II) ion.
5) Write a balanced Net Ionic Equation for the redox reaction:
a) How many electrons are transferred in the process?6) The rate of weathering /dissolution of iron pyrite(Reaction #1), which is an exothermic process is relatively slow, but the dissolution rate increases dramatically with iron pyrite reacting with iron(III) ion, (Reaction #5), which is also exothermic. Draw an energy diagram illustrating the reactions on the same diagram and describe the respective differences in their Energy of Activation.7) Using chemical equations, solubility principles, Ksp, and pH, briefly explain how pH control in the Qual Separation Scheme for separating Group 2 from Group 3 metal ions as their sulfides relate to the leaching of iron and copper into the streams that feed the Sacramento River.Atomic Absorbtion (AA) analysis of a statistically significant number of samples of streams near Iron Mountain's water outfall resulted in an average concentration that suggests 1.5 x 104 moles of iron pyrite dissolve per day.
8) Using the AA results calculate how many tons (1 ton = 1,000 kg) of iron pyrite dissolve per year and how many tons of iron(II) ion is added to the streams and river per year. Show your calculations.The chemistry of limestone cave formation is similar in some ways to the remediation steps taken to treat the toxic mine waste.
9) Describe the similarities using chemical equations.