Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Agenda 1/28/2013 • Turn in work that is due or had been missing • Standard check – 3f and 3c (3b, 3d) • Limiting reactants and percent yield (mandatory listening/write 2 definitions) • “A” Student Assignment • The Mole is a number…(mandatory notes) • Computer lab /Project peer review, spelling, formatting check (MLA) • Homework – complete “World’s …est” Article. Due 11:30 pm Weds turnitin.com Limiting Reactants (or why do reactions stop?) wood + oxygen in air →water vapor + carbon dioxide What is the limiting reactant? Why use an excess of a reactant? Why not use exact mole ratios given in balanced equation? Some reactions stop before reach completion (probability of collisions) inefficient/wasteful Why use an excess of a reactant? Cont. Over time scientists have found often more efficient to use an excess of one reactant (least expensive) “drives” reaction until all limiting reactant used up Can also speed up a reaction Why use an excess of a reactant? Limited air (oxygen) yellow – glowing bits of unburned fuel (sooty) Correct fuel/oxygen ratio – complete combustion Stoichiometry This is the slide that must be copied. Section 12.3 Limiting Reactants Use your text to define each term. New Vocabulary limiting reactant excess reactant 164 Stoichiometry This is the slide that must be copied. Section 12.3 Limiting Reactants Use your text to define each term. New Vocabulary limiting reactant excess reactant 164 Limits the extent of the chemical reaction and thereby determines the amount of product Stoichiometry This is the slide that must be copied. Section 12.3 Limiting Reactants Use your text to define each term. New Vocabulary limiting reactant excess reactant 164 Limits the extent of the chemical reaction and thereby determines the amount of product “leftover” or unused reactants in a chemical reaction Percent Yield Fe2O3 + 3CO →2Fe + 3CO2 • 1 mole (160g) of iron (III) oxide will produce 2 moles of pure iron (2 x 56)g or 112g • 112g is the “theoretical yield” (maximum amount of product possible • In practice what happens? • Get less than expected, say 110g “actual yield” Percent Yield Fe2O3 + 3CO →2Fe + 3CO2 Percent yield = actual yield (from experiment) x 100 Theoretical yield(from stoichiometric calculation) • 112g is the “theoretical yield” for Fe • 110g “actual yield” of Fe Percent yield Fe = 110g x 100 = 98% 112g “A” Student Assignment – Deadline Friday, February 8th Read section 12.3 Limiting Reactants Complete notes page 165, 1st 2 sub-headings only (stop when you get to Determining the Limiting Reactant). Read section 12.4 Percent Yield Complete notes pages 167, 168, and 169 On lined paper complete Section 12.3 Assessment Questions 22 through 26 and Section 12.4 Assessment Questions 30 through 34. Create suitable titles. To turn this work in the three Science notebook pages and the separate papers all need to be stapled together before class. Name need only be written on first page. Carbon-12 isotope is stable and readily available all over the world The Mole is the SI base unit for the amount of a substance. The quantity one mole is set by defining one mole of carbon-12 atoms to have a mass of exactly 12 grams. (CST 3b) The Mole as a Number of Particles This we already should know Standard 3c “representative particles” The mole is the SI unit to measure the amount of a substance. 12g of carbon-12 is set to define one mole and contains one mole of carbon-12 atoms. One mole equals 6.02 x 1023 particles of the substance (atoms, molecules, ions). The Mole is a Unit song http://www.youtube.com/watch?v=1R7NiIum2TI&NR=1 Think about how we assign a name to numbers all the time: A dozen eggs/roses/bread rolls 2 dozen 5 dozen million = 1 000 000 =1.0 x 106 23 10 The Mole is 6.02 x particles (Avogadro’s constant) Fe2O3 + 3CO → 2Fe + 3CO2 1 mole 3 moles 2 moles 3 moles 6.02 x 1023 (formula units) Fe2O3 3 x (6.02 x 1023) = 18.0 x 1023 = 1.80 x 1024 molecules of CO The Mole is 6.02 x particles 23 10 Fe2O3 + 3CO → 2Fe + 3CO2 1 mole 3 moles 2 moles 3 moles 2 x (6.02 x 1023) atoms Fe 12.0 x 1023 = 1.2 x 1024 3 x (6.02 x 1023) = 18.0 x 1023 = 1.80 x 1024 molecules of CO2 Scientific Notation – Appendix B p 889-891 http://www.nyu.edu/pages/mathmol/textbook/scinot.html CST Question – When methane gas is burned in the presence of oxygen, the following chemical reaction occurs Combustion & Exothermic reaction CH4(g) + 2O2(g) CO2(g) + 2H2O(g) If 1 mole of methane reacts with 2 moles of oxygen, then (and the answers are in …. Molecules of CO2 and H2O. What do you do? CST Questions – convert from number of moles to number of molecules by multiplying the number of moles by NA (Avogadro’s constant) CH4(g) + 2 O2(g) 1 mole 2 moles CO2(g) + 2 H2O(g) 1 mole 6.02x1023 6.02x1023 Molecules CO2 2 moles 2x(6.02x1023) 1.20x1024 molecules H2O Get used to it/comfortable with it 1 mole 2 moles 3 moles 6.02 x 1023 particles 2x(6.02x1023) = 1.20x1024 3(6.02 x 1023) = 1.8 x 1024 10 moles 10(6.02 x 1023) = 6.02 x 1024 0.5 moles 0.5(6.02 x 1023) = 3.01 x 1023 0.25 moles 0.25(6.02 x 1023) = 1.5 x 1023 0.1 moles 0.1(6.02 x 1023) =6.02 x 1022 Avogadro’s Principle: equal volumes of gases at the same temperature and pressure contain equal numbers of particles. 22.4L 22.4L He H2 Cl2 28.2 cm 28.2 cm 22.4L 22.4L Molar Volume: A mole (6.02 x 1023 particles) of any gas occupies 22.4 L at STP (0°C which is 273 K and 1 atm). Planning Mon Jan Feb Tue s Weds 22 30 3d and ionic names Project 4 ionic names & review 6Test – Ch 6, 7, all mole, equations, naming cmpds hol Fri 24 (3e) Mass/equ ations 28 mole/no. of particles 3c,d Computer lab time (peer review) hol Thurs 12 8 Lab 5wk Grades 14 20 22 lab