Chem 106: Class/ Lab Week 9 Sign in: Roster @ front of lab Work with your fermentation partner(s) for today’s experiment Chemical Reactions / Stoichiometry Take out your i-clicker

Question Which of the following bonds is the most polar? A) B) C) D)

Answer Which of the following bonds is the most polar? A) B) C) D) 3

What molecular shape is water? Tetrahedral Bent Trigonal planar Linear Note that this question does not require expanded octets. Goal: Connect Lewis structure of a familiar molecule to the name of the molecule geometry Correct answer: B Representative results from pre-general chemistry: 60-67% correct (remaining votes roughly split between C and D) Follow-up discussion: Ask students about the lewis structure of water. Use the simulation (either the model or real molecules screen) to demonstrate the answer once a Lewis structure is agreed upon.

What molecular shape is water? Tetrahedral Bent Trigonal planar Linear Note that this question does not require expanded octets. Goal: Connect Lewis structure of a familiar molecule to the name of the molecule geometry Correct answer: B Representative results from pre-general chemistry: 60-67% correct (remaining votes roughly split between C and D) Follow-up discussion: Ask students about the lewis structure of water. Use the simulation (either the model or real molecules screen) to demonstrate the answer once a Lewis structure is agreed upon.

Which of these molecules has a linear molecule geometry? CO2 O3 Both Neither Note that this question does not require expanded octets. Goal: Extend students application of VSEPR to unfamiliar molecules (carbon dioxide is frequently shown in textbooks as an examples, so many students recall their structure from memory without the need to apply geometry modelling or VSEPR). Ozone is less familiar. Correct answer: A Representative results from pre-general chemistry: 52% correct (next most popular answer is C) Follow-up discussion: Ask students about the lewis structure of each. Use the simulation (either the model or real molecules screen) to demonstrate the answer once a Lewis structure is agreed upon. Follow-up slide can also be shown. Note: While SO2 provides a more obvious contrasting case to CO2 than O3 does (and SO2 is shown in the real molecules screen of the sim), we chose to use ozone to avoid both the use of expanded octets. Additionally, there is some controversy concerning the best Lewis structure for SO2 which instructors should be aware of. Some textbooks treat it as analogous to O3, with one single and one double bond, while others give it two single bonds and an extra lone pair on S (as shown in the simulation). Both Lewis structures lead to a bent geometry.

Which of these molecules has a linear molecule geometry? CO2 O3 Both Neither Note that this question does not require expanded octets. Goal: Extend students application of VSEPR to unfamiliar molecules (carbon dioxide is frequently shown in textbooks as an examples, so many students recall their structure from memory without the need to apply geometry modelling or VSEPR). Ozone is less familiar. Correct answer: A Representative results from pre-general chemistry: 52% correct (next most popular answer is C) Follow-up discussion: Ask students about the lewis structure of each. Use the simulation (either the model or real molecules screen) to demonstrate the answer once a Lewis structure is agreed upon. Follow-up slide can also be shown. Note: While SO2 provides a more obvious contrasting case to CO2 than O3 does (and SO2 is shown in the real molecules screen of the sim), we chose to use ozone to avoid both the use of expanded octets. Additionally, there is some controversy concerning the best Lewis structure for SO2 which instructors should be aware of. Some textbooks treat it as analogous to O3, with one single and one double bond, while others give it two single bonds and an extra lone pair on S (as shown in the simulation). Both Lewis structures lead to a bent geometry.

Which molecule could be represented with this diagram? BH3 CH4 NH3 NH4+ Note that this question does not require expanded octets. Goal: Connect 3D representations to students’ Lewis structure drawings, contrasting the first row elements. Correct answer: C Representative results from pre-general chemistry: 70-80% correct (next most popular answer is A) Follow-up discussion: Ask students about the number of valence electrons of B vs N.

Which molecule could be represented with this diagram? BH3 CH4 NH3 NH4+ Note that this question does not require expanded octets. Goal: Connect 3D representations to students’ Lewis structure drawings, contrasting the first row elements. Correct answer: C Representative results from pre-general chemistry: 70-80% correct (next most popular answer is A) Follow-up discussion: Ask students about the number of valence electrons of B vs N.

Chem 106: Class/ Lab Week 9 Turn in Today Today’s experiment Moles & Molar Masses Weighing as a Way of Counting (Course/ Lab Manual pp. 33-37) Moles & Molar Masses II Atoms / Compounds / Molecular Formulas (Course/ Lab Manual pp. 38-39) Today’s experiment Chemical Reactions / Stoichiometry Have Course/ Lab Manual pp. 49 signed

(Course/ Lab Manual pp. 33-37) Due today. One per Molview Team.

(Course/ Lab Manual pp. 38-39) Due Today: Turn in one per Team or Individually

DUE: Today before midnight http://chemconnections.org/general/chem106/Mole-Quiz.html DUE: Today before midnight

Types of Chemical Reactions Today’s experiment Types of Chemical Reactions Combination (Synthesis) Decomposition Single Displacement Double Displacement Combustion: Oxidation-Reduction Biological Reactions: Enzyme Catalysts Example: Fermentation _______________ A 3900-year-old clay tablet, which was found in Iraq between the Tigris and Euphrates rivers, had a Sumerian poem (http://www.piney.com/BabNinkasi.html) honoring Ninkasi, the patron goddess of brewing. It contains the oldest surviving beer recipe, describing the fermentation of the carbohydrates found in bread, bappir, made from barley, honey, dates and sweet aromatic herbs. The global availability of carbohydrates and native microbes (yeasts) has led to the production of many different types of beers, ales, wines, and fruit based alcoholic beverages in many countries throughout the world. [The bottle on the left was found in Eugene, Oregon, ……. But, it dates only to 2016.] http://www.piney.com/BabNinkasi.html)

General Chemical Reactions http://chemconnections.org/general/movies/rxn-types.mov

https://www.youtube.com/watch?v=OKRJ73Ro5jw https://www.youtube.com/watch?v=rL14uLbSLLc

Human Circadian Rhythm Oscillating Reactions & Homeostasis Begin Here (1 cycle 24 hour Clock)

Chemical Reactions Lab Manual pp. 47-51 All pages are to be completed and turned in next week. Chemical Reactions   Lab Manual pp. 47-51 Complete all of the procedures/reactions for parts A-D; record your observations in Lab Manual; have stamped before leaving lab today. Part A: Synthesis (Combination) Reaction Part B: Decomposition Reactions Part C: Single Replacement Reactions Part D: Double Replacement Reactions

Chemical Reactions Combination (Synthesis) A + B C H2 (g) + O2 (g) H2O (g) Balancing/ Stoichiometry (Conservation of Atoms): H2 (g) + O2 (g) 2 H2O (g) https://www.youtube.com/watch?v=a6qGIMqDKwA

Chemical Reactions Decomposition A B + C 2 NI3 (s) N2 (g) + 3 I2 (s)

Chemical Reactions Single Displacement AB + C CB + A Example: HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g) Balanced Equation: ? 2 HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g) Name HCl(aq) ? Hydrochloric acid

Single Displacement Cu(s) + 2 AgNO3(aq) 2 Ag(s) + Cu(NO3)2 (aq)

Chemical Reactions Double Displacement AB + CD AD + CB Example: A solution of sodium phosphate reacts with a solution of silver nitrate to produce aqueous sodium nitrate and a precipitate of silver phosphate. Balanced equation: ? Na3PO4 (aq) + 3 AgNO3 (aq) Ag3PO4 (s) + 3 NaNO3 (aq)

Double Displacement Predict the products: H2SO4(aq) + NaOH(aq) → H2SO4(aq) + NaOH(aq) → H2O(l) + Na2SO4(aq) Balance the equation: H2SO4(aq) + 2 NaOH(aq) → 2 H2O(l) + Na2SO4(aq)

Chemical Equations Combustion: C8H18(l)+ O2(g) CO2(g) + H2O(l) Oxygen reacts with octane to produce carbon dioxide and water. Reminder: the equation must balance: 2 C8H18(l)+ 25 O2(g) 16 CO2(g)+18 H2O(l) Carbon is oxidized: looses 4 electrons Oxygen is reduced: gains 2 electrons

Combustion Products Formulas & Multiple Proportions http://chemconnections.org/general/movies/multiple-proportions.MOV

Oxidation-Reduction Reactions “Redox” Oxidation is the loss of electrons. Reduction is the gain of electrons. The reactions occur together. One does not occur without the other. The terms are used relative to the change in the oxidation state or oxidation number of the reactant(s).

Activity increases going up the row Activity increases going down the row Activity increases going up the row https://www.youtube.com/watch?v=UO0CKJ0ubwM Cesium: https://www.youtube.com/watch?v=D4pQz3TC0Jo Which would be most reactive? A) Li + I2 B) Na + Cl2 C) Cs + F2 Rubidium: https://www.youtube.com/watch?v=iP6CRZdDu6o

Reactions, Balancing, Stoichiometry Worksheet (Course/ Lab Manual pp Reactions, Balancing, Stoichiometry Worksheet (Course/ Lab Manual pp. 65-67) Due next week. Either work collaboratively and turn in one per partnership or work individually. The Mole / Molar Mass and Molecular Formula On-line Quiz DUE Today 11:59PM. Prepare answers to the following questions for next week.

https://www.youtube.com/watch?v=c5orJHRHbX0