Unit 4: Industry Debate: Chemical Plant in Riverwood? - EKS Nitrogen Products Company OR - WYE Battery Technology Corporation

Figure 5.11 – Page 515 Legumes have nitrogen fixing bacteria on their roots  increase amt of usuable nitrogen for plants in the soil

Figure 5.3 – Page 507 EKS fact: 3 million tons of ammonia, NH3, and 1.5 million tons of nitric acid are produced annually mainly for manufacturing fertilizers.

Background on EKS Nitrogen Products Potassium Phosphorous Nitrogen Ammonium, potassium and Iron cations Nitrate, phosphate, and sulfate anions Key components in Fertilizer

Figure 5.8 – Page 513 Ammonia get used directly to synthesize amino acids. Nitrate ions are also used to synthesize amino acids Plants with nitrogen-fixing bacteria take N2 from air and convert it to a “plant usable form” NH3 or NH4

Figure 5.13 – Page 517

Commercial Production of Ammonia “world production of commercial fertilizer has increased dramatically over the past 65 years” (US annual ~ 20 BILLION pounds of ammonia) Haber-Bosch process current method for production of ammonia (1909 - Germany) N2 + 3 H2 ⇌ 2 NH3   (ΔH = −92.22 kJ·mol−1) Future techniques could include genetic engineering - plants would contain genes that will direct the production of nitrogen fixing enzymes. “Scientists are exploring biological methods for making atmospheric nitro-gen more available to plants. These methods include engineering some microorganisms and plants to contain genes that will direct the production of nitrogen fixing enzymes – thus producing their own nitrogen-based fertilizers” –pg.514

Reaction rates Section B: Kinetics (speed) & Equilibrium (reversible reactions)

2 main reasons rxns occur: (the driving forces) WHAT DETERMINES THE SPEED OF THE RXN?? 1. Energy Spread 2. Matter spread this can occur in opposition - ex: table salt dissolving in water. RXN RATES: COLLISION THEORY 1. COLLISION FREQUENCY 2. ORIENTATION 3. ACTIVATION ENERGY Chemical Kinetics – study of how fast chemical reactions occur

Collision Theory: Why does a tomato take 3 weeks to ripen versus Atoms, ions, and molecules can react to form products when they collide, provided the particles have enough Kinetic energy. Why does a tomato take 3 weeks to ripen versus forming fossil fuels such as oil takes millions of years?

Collision frequency (concentration & temp): The effect of TEMPERATURE on rxn rates: As temp , the rate of rxn (typically the rate of rxn doubles for every 10 C rise in temp) WHY? 1. Heating will cause the particles to move faster –> this increases the frequency in which particles will collide 2. it increases the KE of the particles so that more are in the activation energy level.

2. orientation: refers to the position of the particles relative to each other (the geometry) at the time of collision

Activation Energy, Ea - the minimum KE that reacting molecules must have in order to react High or low? What is the Ea when the reaction is instantaneously spontaneous? What is the Ea when the reaction is slow to start?

Summary: factors influencing rxn rates: Collision frequency Orientation of the molecules Activation Energy

effect of catalyst on rxn rates Catalyst: speeds up the rate of the rxn without being consumed by the reaction. Ex: HCl (not always)-zinc iodide lab –acidified water, Enzymes (catalysts in living systems) ****They work by lowering the activation energy****

Practice: A lump of sugar can be held in your hand (at body temp) without it reacting with oxygen. Holding a match under the lump of sugar does not ignite it. If the sugar is swallowed and metabolized by your body, carbon dioxide and water are produced, and energy is released. A. What does the info tell us about the activation energy for the oxidation of sucrose? B. How could it be possible for the oxidation of sugar to occur in the body at 37C but not when held in the hand at same temp or heated with a flame? C. Is this an exothermic or endothermic rxn?

What is chemical equilibrium? Type of reaction: Macroscopic level definition: Molecular level definition: Chemical equilibrium – when rates of the forward and reverse reaction are equal. Dynamic equilibrium – both forward and reverse reactions continue to proceed but because their rates are equal, no net change occurs in the concentration of the reaction components. Equilibrium position – lies to the left or lies to right

Let’s clarify equilibrium If a reaction is at equilibrium, does that mean there are equal amounts of products and reactants?

SHIFTING THE EQUILIBRIUM

Rate versus Amount

Applying kinetics/equilibrium to Haber-Bocsh Process N2 + 3 H2 ⇌ 2 NH3   (ΔH = −92.22 kJ·mol−1) Reversible Reaction with a high activation energy How do chemical engineers at EKS overcome these obstacles to produce ammonia? Fast and produce more product! Re-write equation with Energy as a product. Look at PE diagram for this reaction (fairly large activation energy required)

Le Chatelier’s Principle LeChatlier’s principle – when a system in equilibrium is disturbed the system will shift in composition until equilibrium has been re-established. Examples of “disturbances” that can cause a shift: Temperature change Pressure change Concentration: Reactants or products added or removed

Le Chatelier’s Principle, con’t. Therefore, there are 4 ways to increase the yield of a product in a gaseous equilibrium reaction: remove product(s) add more reactant(s) change the volume of the container in order to change gas pressure change the temperature

Using Le Chatelier’s principle: How could you increase yield of these reactions? CO2(g) + H2(g) CO(g) + H2O(g), endothermic 4CuO(s) 2Cu2O(s) + O2(g) 2SO2(g) + O2(g) 2SO3(g), -DH

From raw materials to products Waste – is anything that is not the desired product Green Chemistry http://www.epa.gov/sciencematters/june2011/princi ples.htm

How do batteries work? What is the chemistry involved in a battery?

Voltaic Cells Voltaic cell - an electrochemical cell that uses a spontaneous chemical rxn to generate an electric current. Components of a voltaic cell: 2 half-cells connected by a wire Salt bridge cathode and anode Alessandro Volta - invented the first voltaic cell (1800)

Electrical Potential – Voltaic Cell – Electrode – Electric Current - Salt Bridge - Electrical Potential (Volts) – the tendency for electrical charge to move thorough an electrochemical cell Voltaic Cell – Electrode – a strip of metal or other conductor serving as a contact between an ionic solution and the external circuit in an electrochemical cell. Electric Current – the flow of electrons

How does a voltaic cell work spontaneously? When you connect 2 metals from different positions on the activity series - it creates a electrical potential energy difference b/w the metals. The greater the activity b/w the two metals, the greater the electrical potential The differing tendency of metals to lose electrons allows an oxidation -reduction to generate electricity!

A battery consists of a number of voltaic cells. Here’s an example of a single “wet” cell. Sulfate Copper is reduced. Zinc is oxidized.

Cathode (half-cell) Copper will be reduced. Consonants.

Anode (half-cell) Zinc will oxidize Vowels.

Zn  Zn2+ + 2e- (3.63 V) Cu2+  Cu + 2e- (-2.53 V) Use oxidation potential series to determine electric potential (“voltage”) of this cell. Zn  Zn2+ + 2e- (3.63 V) Cu2+  Cu + 2e- (-2.53 V) Difference in electric potential is 1.10 V. Sulfate Copper is reduced. Zinc is oxidized.

Batteries - dry voltaic cell Converting Chemical energy --> electrical energy. anode = zinc cathode = graphite rod salt bridge is replaced by the MnO2 paste - it keeps the contents of the cell from freely mixing. Voltaic Pile

How Batteries Work Common battery chemistries include: Zinc-carbon battery: common in many inexpensive AAA, AA, C and D dry cell batteries. The anode is zinc, the cathode is manganese dioxide, and the electrolyte is ammonium chloride or zinc chloride. Alkaline battery: common in AA, C and D dry cell batteries. The cathode is composed of a manganese dioxide mixture, while the anode is a zinc powder. Lithium-ion battery (rechargeable):, such as cell phones, digital cameras and even electric cars. A variety of substances are used in lithium batteries, such as lithium cobalt oxide cathode and a carbon anode. Lead-acid battery (rechargeable): This is the chemistry used in a typical car battery. The electrodes are usually made of lead dioxide and metallic lead, while the electrolyte is a sulfuric acid solution.

How do car batteries work? How they work!

A 9 V battery consists of six 1 A 9 V battery consists of six 1.5 V batteries (like AAA batteries) wired in series. Capacity refers to how many electrons the series redox reactions will release before no more reactants remain. We will measure this quantity in MOLES of electrons. It is related to the lifetime of the battery. Voltage is proportional to the amount of potential energy each electron gains in the reaction. It is related to the power the battery can provide.

Lead and lead-oxide strips are placed in sulfuric acid Lead and lead-oxide strips are placed in sulfuric acid. What is oxidized? Which is reduced? Car Battery

Lead and lead-oxide strips are placed in sulfuric acid Lead and lead-oxide strips are placed in sulfuric acid. What voltage is generated? Lead is oxidized. Lead oxide is reduced. Car Battery

Lead and lead-oxide strips are placed in sulfuric acid Lead and lead-oxide strips are placed in sulfuric acid. What voltage is generated? 3.22 V - 1.18 V = 2.04 V Lead is oxidized. Lead oxide is reduced. Car Battery

Lithium Ion Batteries Anode – carbon Cathode - lithium compound ex: LiCoO2 LiNiMnCoO2 (NMC) LiFePO4 Electrolyte – organic solvent and a Lithium salt How it works: lithium ions move from the carbon anode through the electrolyte to the cathode where they attach.

Life Cycle of Batteries Recycling Car Batteries Lithium Ion Rechargable