Green Chemistry Workshop #2: Analytical Chemistry I US – Thai Distance Learning Program January 27, 2010 Professor Kenneth M. Doxsee University of Oregon

The Principles of Green Chemistry 1.Prevention 2.Atom Economy 3.Less Hazardous Synthesis 4.Designing Safer Chemicals 5.Safer Solvents and Auxiliaries 6.Design for Energy Efficiency 7. Renewable Feedstocks 8. Reduce Derivatives 9. Catalysis 10. Design for Degradation 11. Real-time Analysis 12. Inherently Safer Chemistry

Oxygen Content of Air Premise Measuring the volume change of air in contact with an Fe(II) solution provides a measure of the percent O 2 in air. Chemical Concepts Acidic, basic, amphoteric oxides; direct combination reactions; preparation and properties of O 2 ; physical nature of reactants; acid and base properties; stoichiometry; redox; gas solubility; volume.

Background Fe(II) oxidizes slowly at pH < 7 Fe(II) oxidizes quickly at pH > 7. This allows us to prepare solutions of Fe(II) in contact with air, then to induce the reaction with O 2 when we are ready.

Reaction Chemistry Fe(II) + O 2 Fe(III) FeSO 4 + O 2 pH < 7 slow Fe(III) pH > 7 fast Fe(OH) 3, Fe 2 O 3, FeOH(SO 4 ), Fe 2 (SO 4 ) 3, …?

Materials Syringe image: Beaker image: Tubing image: two 1 mL syringes 0.4 mL of 0.2 M FeSO mL of 2 M NaOH 1 cm tubing

Apparatus and Procedure 1 cm flexible transparent tubing (filled with 2 M NaOH) 0.4 mL of 0.2 M FeSO mL of 2 M NaOH mL of air measure initial volume of air carefully!! measure final volume of air carefully!!

Calculations Check limiting reagent: 0.4 ml of 0.2 M FeSO 4 = 8.0 x moles Fe(II) 0.5 mL of air ~ 0.1 mL of O 2 = 4.1 x mole O 2 PV = nRT N = PV/RT = (760 mm-Hg)(0.001 L) ( L-mmHg-mol -1 -K -1 )(298 K) There is enough Fe(II) to consume all the O 2. R= L-atm-mol -1 K -1 = L-mmHg-mol -1 -K -1

Calculations V final - V initial = V O2 % O 2 in air = (V O2 /V initial ) x 100%

Laboratory Safety Accident: An unexpected and undesirable event, especially one resulting in damage or harm. Image from:

LABORATORY SESSION Break for ….

Calculations V final - V initial = V O2 % O 2 in air = (V O2 /V initial ) x 100%

Other Approaches Orsat analyzers (alkaline pyrogallic acid and/or chromium (II) chloride solutions) Electrochemical determinations Quenching of room-temperature phosphorescence Quenching of luminescence Use of a paramagnetic oxygen analyzer  Hazardous reagents (exposure risks, waste disposal)  Specialized equipment (expensive to purchase and operate) Orsat analyzer image: Paramagnetic O 2 analyzer image:

Green Relevance Green Concepts Safer chemicals and solvents – compare reagents used in other determinations of oxygen content. Prevention of waste. Consider Green Principles – #1 (prevent waste) – #2 (atom economy) – #3 (use less hazardous substances) – #8 (avoid derivatives) – #10 (design for degradation) – #11 (real time monitoring) – #12 (use substances in forms that minimize hazards).

CaCO 3 Content of Eggshells Premise CaCO 3 reacts with acids to produce CO 2. By measuring the volume of CO 2 produced, we can determine how much CaCO 3 was present in a sample of eggshell of known mass. Chemical Concepts Decomposition reactions; reactivities of oxides; preparation of CO 2 ; acid-base properties; stoichiometry; gas law.

Background Eggshells are constituted primarily of calcite – a crystalline form of CaCO 3. Shell formation is governed by LeChatelier´s principle. Carbonate ions are produced by: CO 2 (g) + H 2 O ⇄ CO 2 (aq) ⇄ H 2 CO 3 H 2 CO 3 ⇄ H+ + HCO 3 - HCO 3 - ⇄ H+ + CO 3 2- Shell and membranes production occurs in a gland of the urogenital system of the female bird: CO 3 2- (aq) + Ca 2+ (aq) ⇄ CaCO 3 (s)

Reaction Chemistry CaCO 3 (s) + 2H + (aq)  Ca 2+ (aq) + H 2 O(l) + CO 2 (g) If the eggshell is treated with an acid, it will dissolve through the reverse of the process by which it is formed. By measuring the volume of CO 2 produced, we can determine how much CaCO 3 was present.

Materials Eggshell image: Scale image: Mortar and pestle image: Plastic caps image: Syringe image: Beaker image: 10 mL 3N HCl 0.2 g crushed egg shell

Apparatus and Procedure measure final volume measure volume 10 mL 3N HCl

Calculations V final - V initial = V CO2 PV= nRT n = moles of CO 2 = PV/RT = moles of CaCO 3 in sample If eggshell were pure CaCO 3 (MW g-mol -1 ): x.xx g x 1 mole/ g = y.yy mole % CaCO 3 = (n/y.yy) x 100% = R= L-atm-mol -1 K -1 = L-mmHg-mol -1 -K -1

Laboratory Safety Accident: An unexpected and undesirable event, especially one resulting in damage or harm. Image from:

LABORATORY SESSION Break for ….

Calculations V final - V initial = V CO2 PV= nRT n = moles of CO 2 = PV/RT = moles of CaCO 3 in sample If eggshell were pure CaCO 3 (MW g-mol -1 ): x.xx g x 1 mole/ g = y.yy mole % CaCO 3 = (n/y.yy) x 100% = R= L-atm-mol -1 K -1 = L-mmHg-mol -1 -K -1

Green Relevance of the CaCO 3 Experiment Green Concepts Waste as a feedstock. Renewable feedstocks. Consider Green Principles – #1 (prevent waste) – #7 (renewable feedstocks) – #3 (use less hazardous substances) – #11 (real time monitoring) – #12 (use substances in forms that minimize hazards).

Questions and Discussion Image from:

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