Lecture 37 Reactions 4 Read HW BLB 4 6 10 5 BLB 4 81a b 83 87 10 28 55 57 18 26 61 Sup Rxns 12 18 Know solution stoichimetry reactions in the gas phase Check out the grad u lator on the Chem110 website Review chemical nomenclature e g BST 5 Lecture 8 memorize those strong acids bases BLB Table 4 2 Bonus deadline for BST 10 Net ionic equations Thurs April 16 FINAL SKILL CHECK TEST DEADLINE MONDAY APRIL 27 Missed Exam 1 2 or 3 due to illness Make up Exam Monday April 20 6 30 105 Wartik Covers material from Exams 1 3 multiple choice You must sign up by downloading completing the request form giving it to me deadline to sign up is TODAY info under Exam Schedule on Chem110 website Need help Get help TAs in CRC 211 Whitmore and SI hours on Chem 110 website my office hours Mon 12 30 2 Tues 10 30 12 in 324 Chem Bldg or 326 Chem F in al Exa m MONDAY May 4 12 20 pm Sheets Page 1 Lecture 37 Example How many liters of N2 at 735 mm Hg and 26 C are produced from 126 g NaN3 sodium azide NaN3 s 65 g mol 126 g Sheets Na s N2 g 23 g mol 28 g mol V P 735 mmHg T 26 C Page 2 Lecture 37 Example 48 6 g Mg reacts with 11 2 L O2 at STP A What is the expected yield theoretical yield of MgO in grams B Which reactant is the limiting reagent and which is in excess C How much of the excess reagent remains after the reaction goes to completion D What is being oxidized What is being reduced Mg s O2 g 24 3 g mol 32 g mol 48 6 g 11 2 L MgO 40 3 g mol P 1 atm T 273 K Sheets Page 3 Lecture 37 previous example con t When you react Mg with O2 in lab you get 32 2 g What is your percent yield Sheets Page 4 Lecture 37 Example The arsenic in a 1 22 g sample of a pesticide was converted to AsO43 by suitable chemical treatment It was then titrated using Ag to form Ag3AsO4 as a precipitate A What is the oxidation state of As in AsO43 B If it took 25 0 mL of 0 102 M Ag to reach the equivalence point in this titration what is the mass percentage of arsenic in the pesticide Ag aq 107 9 g mol 25 00 mL 0 102 M Sheets AsO43 aq 138 9 g mol Ag3AsO4 s 462 6 g mol mass of As in 1 22 g pesticide Page 5 Lecture 37 Example In an explosion a compound that is a solid or a liquid decomposes very rapidly producing large volumes of gas The force of the explosion results from the rapid expansion of the hot gases For example TNT trinitrotoluene explodes according to the reaction shown below A Balance this chemical equation B How many moles of gas are produced in the explosion of 1 0 kg of TNT C What volume will these gases occupy if they expand to a total pressure of 1 0 atm at 298 K D At 1 0 atm total pressure what would be the partial pressure of each gas NO2 C HC O2 N C C CH Vtot C P 1 0 atm NO2 CH3 C7H5 NO2 3 s 227 g mol 1 0 kg Sheets T 298K CO g C s H2 g N2 g 28 g mol 12 g mol 2 g mol 28 g mol PCO PH2 PN2 Page 6 Lecture 37 Does X 1 000 i Does Ptot P i Always check your answers to see whether they make sense Sheets Page 7 Lecture 37 Example What spectator ions are present when HClO4 aq reacts with Ca OH 2 aq H HCl O2 ClO4 Ca2 OH Sheets Page 8 Lecture 37 Before next class Read HW BLB 5 3 5 5 BLB 5 4 6 17 29 37 39 41 53 55 Know energy enthalpy enthalpy of reactions calorimetry Answers p 2 73 8 L p 3 a 40 3 MgO b O2 is LR c 24 3 g excess Mg d Mg oxidized O reduced p 4 79 9 p 5 a 5 b 5 23 p 6 b 44 1 mol c 1078 L d PCO 0 60 atm PH2 0 25 atm PN2 0 15 atm p 8 Ca2 ClO4 Sheets Page 9 Lecture 37
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