ERTH 3222 Bio-Geo-Chemical Reactions Flashcards

Flashcards covering biogeochemical reactions, microbial processes, bioleaching, and mineral transformations from ERTH 3222 lecture notes.

What is the name and ionic charge of $Fe^{2+}$?

Ferrous ion, charge of $+2$.

What is the name and ionic charge of $Fe^{3+}$?

Ferric ion, charge of $+3$.

What is the name and ionic charge of $SO_4^{2-}$?

Sulfate ion, charge of $-2$.

What is the name and ionic charge of $NO_3^-$?

Nitrate ion, charge of $-1$.

What is the name and ionic charge of $HCO_3^-$?

Bicarbonate ion, charge of $-1$.

What is the name and ionic charge of $UO_2^{2+}$?

Uranyl ion, charge of $+2$.

What is the name and ionic charge of $TcO_4^-$?

Pertechnetate ion, charge of $-1$.

What is the name and ionic charge of $S_2O_3^{2-}$?

Thiosulfate ion, charge of $-2$.

What are the chemical formulas and charges for native gold vs the ionic gold species in the document?

Native gold is $Au^0$ (charge $0$). Ionic gold species are aurous $Au^+$ (charge $+1$) and auric $Au^{3+}$ (charge $+3$).

Identify the reaction process: $6CO_2 + 6H_2O + \text{photons} \rightarrow C_6H_{12}O_6 + 6O_2$

Oxygenic Photosynthesis (standard reaction)

Identify the reaction process: $2NO_3^- + 5H_2 \rightarrow N_{2(g)} + 2OH^- + 4H_2O$

Denitrification

Identify the reaction process: $UO_2^{2+} + H_2 \rightarrow UO_{2(s)} + 2H^+$

Uranium Reduction

Identify the reaction process: $TcO_4^- + 1\frac{1}{2}H_2 \rightarrow TcO_{2(s)} + OH^- + H_2O$

Technetium Reduction

Identify the reaction process: $H_2S + 2Au^+ \rightarrow 2H^+ + Au^0$

Effect of SRB on Ionic Gold

Write the complete balanced equation for Oxygenic Photosynthesis (standard reaction).

$$6CO_2 + 6H_2O + \text{photons} \rightarrow C_6H_{12}O_6 + 6O_2$$

Write the complete balanced equation for Oxygenic Photosynthesis (bicarbonate reaction).

$$6HCO_3^- + 6H_2O + \text{photons} \rightarrow C_6H_{12}O_6 + 6O_2 + 6OH^-$$

Write the complete balanced equation for Mineral Carbonation.

$$Ca^{2+} + HCO_3^- + OH^- \rightarrow CaCO_{3(s)} + H_2O$$

Write the complete balanced equation for Aerobic Heterotroph Respiration.

$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$$

Write the complete balanced equation for Methane Oxidation.

$$CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$$

Write the complete balanced equation for Decane Oxidation.

$$C_{10}H_{22} + 15\frac{1}{2}O_2 \rightarrow 10CO_2 + 11H_2O$$

Write the complete balanced equation for Biological Iron Oxidation.

$$4Fe^{2+} + O_2 + 4H^+ \rightarrow 4Fe^{3+} + 2H_2O$$

Write the complete balanced equation for Ferric Iron Hydrolysis.

$$Fe^{3+} + 3H_2O \rightarrow Fe(OH)_{3(s)} + 3H^+$$

Write the complete balanced equation for Sulfur Oxidation by Bacteria.

$$S^0 + 1\frac{1}{2}O_2 + H_2O \rightarrow SO_4^{2-} + 2H^+$$

Write the complete balanced equation for Denitrification.

$$2NO_3^- + 5H_2 \rightarrow N_{2(g)} + 2OH^- + 4H_2O$$

Write the complete balanced equation for Sulfate Reduction using Acetate (Desulforudis audaxviator).

$$CH_3COOH + SO_4^{2-} \rightarrow H_2S + 2HCO_3^-$$

Write the complete balanced equation for Sulfate Reduction using Hydrogen (Desulforudis audaxviator).

$$4H_2 + SO_4^{2-} \rightarrow H_2S + 2OH^- + 2H_2O$$

Write the complete balanced equation for Black Precipitate Reaction in a Winogradsky Column.

$$H_2S + Fe^{2+} \rightarrow FeS_{(s)} + 2H^+$$

Write the complete balanced equation for Uranium Reduction.

$$UO_2^{2+} + H_2 \rightarrow UO_{2(s)} + 2H^+$$

Write the complete balanced equation for Technetium Reduction.

$$TcO_4^- + 1\frac{1}{2}H_2 \rightarrow TcO_{2(s)} + OH^- + H_2O$$

Write the complete balanced equation for Hydrogenotrophic Methanogenesis.

$$4H_2 + CO_2 \rightarrow CH_{4(g)} + 2H_2O$$

Write the complete balanced equation for Acetoclastic Methanogenesis.

$$CH_3COOH \rightarrow CH_{4(g)} + CO_{2(g)}$$

Write the complete balanced equation for Serpentinised Olivine.

$$9Mg_2(\text{Ni})SiO_4 + 3Fe_2(\text{Ni})SiO_4 + 14H_2O \rightarrow 6Mg_3Si_2O_5(OH)_4 + 2Fe_3O_4 + 2H_2$$

Write the complete balanced equation for Manganese Oxidation.

$$Mn^{2+} + H_2O + \frac{1}{2}O_2 \rightarrow MnO_2 + 2H^+$$

Write the complete balanced equation for Complete Pyrite Oxidation by Ferric Iron.

$$FeS_2 + 14Fe^{3+} + 8H_2O \rightarrow 15Fe^{2+} + 2SO_4^{2-} + 16H^+$$

Write the complete balanced equation for Partial Pyrite Oxidation by Ferric Iron (forming elemental sulfur).

$$FeS_2 + 2Fe^{3+} \rightarrow 3Fe^{2+}_{(aq)} + 2S^0$$

Write the complete balanced equations for Supergene Enrichment of Copper via Disproportionation and Precipitation.

$$2S^0 + H_2O \rightarrow S^{2-} + SO + 2H^+$$

$$Cu^{2+} + S^{2-} \rightarrow CuS_{(s)}$$

Write the complete balanced equation for Chalcocite Leaching.

$$Cu_2S_{(s)} + 8Fe^{3+} + 4H_2O \rightarrow 2Cu^+ + 8Fe^{2+} + SO_4^{2-} + 8H^+$$

Write the complete balanced equation for Covellite Leaching.

$$CuS_{(s)} + 8Fe^{3+} + 4H_2O \rightarrow Cu^{2+} + 8Fe^{2+} + SO_4^{2-} + 8H^+$$

Write the complete balanced equation for Chalcopyrite Leaching.

$$CuFeS_{2(s)} + 16Fe^{3+} + 8H_2O \rightarrow Cu^{2+} + 17Fe^{2+} + 2SO_4^{2-} + 16H^+$$

Write the complete balanced equation for Carbonate Buffering.

$$CaCO_{3(s)} + 2H^+ \rightarrow Ca^{2+} + H_2O + CO_{2(g)}$$

Write the complete balanced equation for Slow Anaerobic Pyrite Formation.

$$FeS_{(s)} + H_2S \rightarrow FeS_{2(s)} + H_2$$

Write the complete balanced equations for Fast Microaerophilic Pyrite Formation (Step 1 and Step 2).

Step 1: $H_2S + \frac{1}{2}O_2 \rightarrow S^0 + H_2O$

Step 2: $FeS_{(s)} + S^0 \rightarrow FeS_{2(s)}$

Write the complete balanced equations for the Biogeochemistry of Gold (Dissolution, Disproportionation, Chloride Complex, Thiosulfate Complex).

Dissolution: $2Au^0 + H_2O_2 \rightarrow 2Au^+ + 2OH^-$

Disproportionation: $3Au^+ \rightarrow 2Au^0 + Au^{3+}$

Chloride Complex: $Au^{3+} + 4Cl^- \rightarrow AuCl_4^-$

Thiosulfate Complex: $Au^+ + 2S_2O_3^{2-} \rightarrow Au(S_2O_3)_2^{3-}$

Write the complete balanced equations for the Effect of Sulfur (Thiosulfate) Oxidising Bacteria on Gold.

Thiosulfate Oxidation: $S_2O_3^{2-} + 2O_2 + H_2O \rightarrow 2SO_4^{2-} + 2H^+$

Gold Complex Breakdown: $Au(S_2O_3)_2^{3-} + 4O_2 + 2H_2O \rightarrow Au^+ + 4SO_4^{2-} + 4H^+$

Write the complete balanced equations for the Effect of Ferric Iron (Iron Oxidising Bacteria) on Gold Thiosulfate.

Iron Oxidation of Thiosulfate: $8Fe^{3+} + S_2O_3^{2-} + 5H_2O \rightarrow 8Fe^{2+} + 2SO_4^{2-} + 10H^+$

Iron Release of Gold: $16Fe^{3+} + Au(S_2O_3)_2^{3-} + 10H_2O \rightarrow 16Fe^{2+} + Au^+ + 4SO_4^{2-} + 2OH^+$

Write the complete balanced equation for

What is the name and ionic charge of $Fe^{2+}$?

Ferrous ion, charge of $+2$.

What is the name and ionic charge of $Fe^{3+}$?

Ferric ion, charge of $+3$.

What is the name and ionic charge of $SO_4^{2-}$?

Sulfate ion, charge of $-2$.

What is the name and ionic charge of $NO_3^-$?

Nitrate ion, charge of $-1$.

What is the name and ionic charge of $HCO_3^-$?

Bicarbonate ion, charge of $-1$.

What is the name and ionic charge of $UO_2^{2+}$?

Uranyl ion, charge of $+2$.

What is the name and ionic charge of $TcO_4^-$?

Pertechnetate ion, charge of $-1$.

What is the name and ionic charge of $S_2O_3^{2-}$?

Thiosulfate ion, charge of $-2$.

What are the chemical formulas and charges for native gold vs the ionic gold species?

Native gold is $Au^0$ (charge $0$). Ionic gold species are aurous $Au^+$ (charge $+1$) and auric $Au^{3+}$ (charge $+3$).

What are six major biogeochemical forms/species of nitrogen?

1. Dinitrogen gas ($N_2$)

2. Nitrate ($NO_3^-$)

3. Nitrite ($NO_2^-$)

4. Ammonium ($NH_4^+$)

5. Ammonia ($NH_3$)

6. Nitrous oxide ($N_2O$) or organic nitrogen (amino acids/proteins).

Why is water ($H_2O$) essential for life and biogeochemical reactions?

Water acts as a universal polar solvent, a transport medium for ions, a reactant/electron donor in photosynthesis, a source of $H^+$ and $OH^-$ for acid-base reactions, and a key agent in mineral hydrolysis and serpentinization.

What is the core pathway of the biogeochemical Carbon Cycle?

Carbon cycles between inorganic oxidized forms ($CO_2$, $HCO_3^-$) and organic reduced forms ($C_6H_{12}O_6$) or reduced gases ($CH_4$) via photosynthesis, respiration, methanogenesis, methane oxidation, and mineral precipitation/dissolution ($CaCO_3$).

What is the core pathway of the Methane Cycle?

Methane ($CH_4$) is produced in anaerobic environments by methanogens (via hydrogenotrophic or acetoclastic pathways) and oxidized back to $CO_2$ by aerobic or anaerobic methane-oxidizing bacteria.

What is the chemical theory behind Oxygenic Photosynthesis?

Autotrophic organisms use light energy (photons) to fix inorganic carbon ($CO_2$ or $HCO_3^-$) into organic matter ($C_6H_{12}O_6$), splitting water and releasing oxygen ($O_2$) as a byproduct.

What is the chemical theory behind Mineral Carbonation?

In aqueous environments, calcium ions ($Ca^{2+}$) react with bicarbonate ($HCO_3^-$) under alkaline conditions ($OH^-$) to permanently sequester carbon into solid calcium carbonate ($CaCO_3$).

What is the chemical theory behind Aerobic Respiration and Hydrocarbon Degradation?

Heterotrophic organisms and hydrocarbon-degrading bacteria oxidize organic molecules ($C_6H_{12}O_6$) or hydrocarbons ($CH_4$, $C_{10}H_{22}$) using oxygen ($O_2$) as the terminal electron acceptor, producing $CO_2$ and $H_2O$.

What is the chemical theory behind Biological Iron Oxidation and Hydrolysis?

Iron-oxidizing bacteria oxidize soluble ferrous iron ($Fe^{2+}$) to ferric iron ($Fe^{3+}$) using oxygen. Ferric iron subsequently hydrolyzes in water to form insoluble ferric hydroxide ($Fe(OH)_3$) precipitate and release protons ($H^+$).

What is the chemical theory behind Bacterial Sulfur Oxidation?

Sulfur-oxidizing bacteria use oxygen to oxidize elemental sulfur ($S^0$) to sulfate ($SO_4^{2-}$), generating sulfuric acid ($H^+$) which drives acid mine drainage and rock weathering.

What is the chemical theory behind Denitrification?

Anaerobic bacteria use nitrate ($NO_3^-$) as a terminal electron acceptor and hydrogen gas ($H_2$) as an electron donor, reducing nitrate to inert dinitrogen gas ($N_{2(g)}$) and generating alkalinity ($OH^-$).

What is the chemical theory behind Sulfate Reduction by Desulforudis audaxviator?

Obligate anaerobes reduce sulfate ($SO_4^{2-}$) using electron donors like acetate ($CH_3COOH$) or molecular hydrogen ($H_2$) to generate hydrogen sulfide ($H_2S$).

What is the chemical theory behind Anaerobic Metal Reduction (Uranium and Technetium)?

Anaerobic bacteria reduce soluble, toxic radionuclides—uranyl ($UO_2^{2+}$) and pertechnetate ($TcO_4^-$)—using $H_2$ to convert them into insoluble oxide precipitates ($UO_{2(s)}$, $TcO_{2(s)}$).

What is the chemical theory behind Methanogenesis?

Strict anaerobic archaea reduce $CO_2$ using $H_2$ (hydrogenotrophic) or split acetate ($CH_3COOH$) (acetoclastic) to generate methane ($CH_{4(g)}$) in oxygen-depleted subsurface environment.

What is the chemical theory behind Olivine Serpentinization?

Anorganic hydrothermal reaction where water oxidizes ferrous iron in olivine minerals ($Mg_2SiO_4$, $Fe_2SiO_4$), forming serpentine minerals, magnetite ($Fe_3O_4$), and abiotic hydrogen gas ($H_2$).

What is the chemical theory behind Manganese Oxidation?

Dissolved manganese ($Mn^{2+}$) is oxidized by oxygen in the presence of water to precipitate solid manganese dioxide ($MnO_2$) and release protons.

What is the chemical theory behind Pyrite Oxidation by Ferric Iron?

Ferric iron ($Fe^{3+}$) acts as a powerful oxidant that attacks pyrite ($FeS_2$). Complete oxidation yields sulfate ($SO_4^{2-}$) and acidity, whereas partial oxidation generates elemental sulfur ($S^0$).

What is the chemical theory behind Pyrite Formation pathways?

Iron monosulfide ($FeS$) transforms into pyrite ($FeS_2$) slowly under anaerobic conditions via reaction with $H_2S$, or rapidly under microaerophilic conditions where trace oxygen generates elemental sulfur ($S^0$) to react with $FeS$.

What is the chemical theory behind Supergene Copper Enrichment and Leaching?

Supergene processes involve elemental sulfur disproportionation to produce sulfide ($S^{2-}$) that precipitates copper as covellite ($CuS$). Acidic ferric iron leaches copper sulfide minerals (chalcocite, covellite, chalcopyrite) to release soluble copper ions.

What is the chemical theory behind Carbonate Buffering?

Calcium carbonate ($CaCO_3$) reacts with excess acidity ($H^+$) to produce dissolved $Ca^{2+}$, water, and carbon dioxide gas ($CO_2$), regulating pH in natural waters.

What is the chemical theory behind Gold Biogeochemistry?

Gold ($Au^0$) is solubilized by oxidative peroxide or complexes with chloride ($Cl^-$) and thiosulfate ($S_2O_3^{2-}$). Bacteria or ferric/sulfur oxidizers break down these complexes, while sulfate-reducing bacteria ($H_2S$) reduce ionic gold back to native gold ($Au^0$) precipitates.

Write the complete balanced equation for Oxygenic Photosynthesis (standard reaction).

$$6CO_2 + 6H_2O + \text{photons} \rightarrow C_6H_{12}O_6 + 6O_2$$

Write the complete balanced equation for Oxygenic Photosynthesis (bicarbonate reaction).

$$6HCO_3^- + 6H_2O + \text{photons} \rightarrow C_6H_{12}O_6 + 6O_2 + 6OH^-$$

Write the complete balanced equation for Mineral Carbonation.

$$Ca^{2+} + HCO_3^- + OH^- \rightarrow CaCO_{3(s)} + H_2O$$

Write the complete balanced equation for Aerobic Heterotroph Respiration.

$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$$

Write the complete balanced equation for Methane Oxidation.

$$CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$$

Write the complete balanced equation for Decane Oxidation.

$$C_{10}H_{22} + 15\frac{1}{2}O_2 \rightarrow 10CO_2 + 11H_2O$$

Write the complete balanced equation for Biological Iron Oxidation.

$$4Fe^{2+} + O_2 + 4H^+ \rightarrow 4Fe^{3+} + 2H_2O$$

Write the complete balanced equation for Ferric Iron Hydrolysis.

$$Fe^{3+} + 3H_2O \rightarrow Fe(OH)_{3(s)} + 3H^+$$

Write the complete balanced equation for Sulfur Oxidation by Bacteria.

$$S^0 + 1\frac{1}{2}O_2 + H_2O \rightarrow SO_4^{2-} + 2H^+$$

Write the complete balanced equation for Denitrification.

$$2NO_3^- + 5H_2 \rightarrow N_{2(g)} + 2OH^- + 4H_2O$$

Write the complete balanced equation for Sulfate Reduction using Acetate (Desulforudis audaxviator).

$$CH_3COOH + SO_4^{2-} \rightarrow H_2S + 2HCO_3^-$$

Write the complete balanced equation for Sulfate Reduction using Hydrogen (Desulforudis audaxviator).

$$4H_2 + SO_4^{2-} \rightarrow H_2S + 2OH^- + 2H_2O$$

Write the complete balanced equation for Black Precipitate Reaction in a Winogradsky Column.

$$H_2S + Fe^{2+} \rightarrow FeS_{(s)} + 2H^+$$

Write the complete balanced equation for Uranium Reduction.

$$UO_2^{2+} + H_2 \rightarrow UO_{2(s)} + 2H^+$$

Write the complete balanced equation for Technetium Reduction.

$$TcO_4^- + 1\frac{1}{2}H_2 \rightarrow TcO_{2(s)} + OH^- + H_2O$$

Write the complete balanced equation for Hydrogenotrophic Methanogenesis.

$$4H_2 + CO_2 \rightarrow CH_{4(g)} + 2H_2O$$

Write the complete balanced equation for Acetoclastic Methanogenesis.

$$CH_3COOH \rightarrow CH_{4(g)} + CO_{2(g)}$$

Write the complete balanced equation for Serpentinised Olivine.

$$9Mg_2(\text{Ni})SiO_4 + 3Fe_2(\text{Ni})SiO_4 + 14H_2O \rightarrow 6Mg_3Si_2O_5(OH)_4 + 2Fe_3O_4 + 2H_2$$

Write the complete balanced equation for Manganese Oxidation.

$$Mn^{2+} + H_2O + \frac{1}{2}O_2 \rightarrow MnO_2 + 2H^+$$

Write the complete balanced equation for Complete Pyrite Oxidation by Ferric Iron.

$$FeS_2 + 14Fe^{3+} + 8H_2O \rightarrow 15Fe^{2+} + 2SO_4^{2-} + 16H^+$$

Write the complete balanced equation for Partial Pyrite Oxidation by Ferric Iron (forming elemental sulfur).

$$FeS_2 + 2Fe^{3+} \rightarrow 3Fe^{2+}_{(aq)} + 2S^0$$

Write the complete balanced equations for Supergene Enrichment of Copper via Disproportionation and Precipitation.

$$2S^0 + H_2O \rightarrow S^{2-} + SO + 2H^+$$

$$Cu^{2+} + S^{2-} \rightarrow CuS_{(s)}$$

Write the complete balanced equation for Chalcocite Leaching.

$$Cu_2S_{(s)} + 8Fe^{3+} + 4H_2O \rightarrow 2Cu^+ + 8Fe^{2+} + SO_4^{2-} + 8H^+$$

Write the complete balanced equation for Covellite Leaching.

$$CuS_{(s)} + 8Fe^{3+} + 4H_2O \rightarrow Cu^{2+} + 8Fe^{2+} + SO_4^{2-} + 8H^+$$

Write the complete balanced equation for Chalcopyrite Leaching.

$$CuFeS_{2(s)} + 16Fe^{3+} + 8H_2O \rightarrow Cu^{2+} + 17Fe^{2+} + 2SO_4^{2-} + 16H^+$$