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Sheets Page 1 Lecture 37 Lecture 37: Reactions 4 Read: BLB 4.6 & 10.5 HW: 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]) Final Exam: MONDAY, May 4, 12:20 pmSheets Page 2 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) Na (s) N2 (g)65 g/mol126 g28 g/mol23 g/molV = ???P = 735 mmHgT = 26°CSheets Page 3 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) MgO48.6 g 11.2 LP=1 atmT=273 K24.3 g/mol 32 g/mol 40.3 g/molSheets Page 4 Lecture 37 previous example conʼt. When you react Mg with O2 in lab, you get 32.2 g. What is your percent yield?Sheets Page 5 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? ???AsO43– (aq)Ag+ (aq)Ag3AsO4 (s)25.00 mL0.102 M??? mass% of As in 1.22 g pesticide107.9 g/mol 138.9 g/mol 462.6 g/molSheets Page 6 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? C7H5(NO2)3(s)CO(g) + C(s) + H2(g) + N2(g)HCCCCCHCCH3O2NNO2NO2227 g/mol 28 g/mol 12 g/mol 2 g/mol 28 g/mol1.0 kgVtot = ???P = 1.0 atmT = 298KPCO = ?? PH2 = ?? PN2 = ??Sheets Page 7 Lecture 37 Does Xi= 1.000? Does Ptot = Pi?!! Always check your answers to see whetherthey make sense!!Sheets Page 8 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 9 Lecture 37 Before next class: Read: BLB 5.3–5.5 HW: 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+,


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PSU CHEM 110 - Reactions 4

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