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exam4key2010sp0001 - i I Chem 10 Spring 2010 Name W Igc 2 I...

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Unformatted text preview: /. / i I Chem 10 Spring 2010 Name W Igc 2 I: i? .. WF 7:45 — 10 am Sec 1315/1316 21 May 2010 ét a earn , EXAM4 K qu M a: 7% 5 ”(m0 Instructions: M "I ’9 l1 ‘1 7‘ 1. There are 100 points in this exam, with five (5) exam pages and 16 questions, including the extra credit problem. Check to make sure you have all the pages. You also have two pages of scratch paper, tables and charts, which you may remove. 2. Put your name or initials on each sheet. Make it readable! 3. For each question below, provide an answer. a. For multiple choice questions, place the correct letter in the space to the left of the question. Ifyou feel more than one answer is correct, put the best answer. The letter must be clear. b. For all others provide an answer in the space provided. Ifyour answer can't be easily read, it won't be graded - and gets no points! ’ 4. No cheating. You may have only a dictionary, writing instmments, an eraser and your own calculator. No other help or talking. You have 65 minutes. When you finish the exam, you may leave. 5. Please come to the front of the room with any questions. Some conversions and formulas 18°C = (°F-32) °C = K—273 1” = 25.4 mm 1 mole of things = 6.022 x 1023, things (Avagadro’s number) 1 gal = 3.803 L l in =2.54 cm 1 yd = 0.9144 In D = m/V 1 lb (pound) = 0.4536 kg 1 lb = 16 oz 1 mi = 5280 ft Density water = 1.0000 g/mL Specific Heats water gas = 2.02 J/gOK, liquid 4.18 Jig-K and solid 2.06 J/ 0K Multiple Choice Questions (10 at 5 points ach or AC a 1. During a certain titration, it took 33.3 mL of 0.250 M potassium hydroxide to exactly neutralize 75.00 mL of sulfuric acid. Determine the molarity of the acid. H2S04 + 2KOH —> 2 H20 +KZSO4 (balanced equation) a. 4.50M b. 0.222M .d..000999M e 0111M i i 2. According to the following equation: ( DHL){_’i°—‘L a“) /- (( ,8?) :1 AgN03 (aq) + NaBr (aq) —> AgBr (s) + NaN03(aq) (balanced) / _ How many grams of AgBr will be produced by the reaction of 75.0 mL of 0.504 M VAgNO3(aq) with excess NaBr? (molar mass of AgBr = 188 g/mol) a. 27.9g b. 0.201 g c. 250g d. 187g e. 7.11 g . 27; l :2 3. A tank containing an ideal gas has a pr§9rde of 30.0 atm at a temperature of 22 0°C. After heating, the temperature rises to 0 0°C What IS the new pressure? Q “W7 a. 18.8atm b. 31.3atm c 28.7atm 300atm e501atm mm 2375 (VZHKT _ £3“me E’den E: HM ILA ’_ {GM/v All): Kbml o: smAT Stomach acid (HCl) at 0.100 M reacts completely with an antacid tablet containing 505 mg of Al(OH)3 [formula mass 78.0 g/mole]. Wh(1 t} vol re of ‘ ‘ ‘ ' $7220 ”(I consumed? The balanced equation is .50!) 3 HCIWD + A1(OH)3 —’ A1C13(aq) + 3 H200) @ b.64.7mL c. 19.4mL d. 21.6mL d.118mL nrcT’ V’ 7F : 2%? What IS the volume occupied by 22. 6 g of gaseous methane W I 1 molar mass of m 16 043 g/mole. 3 o l a. 2.11 L w c. 214 L d. 2230 L e. 5640 L How many grams of potassium chromate, K2004, will be needed to make 250.0 mL of 0.500 M solution? The molar mass ofKZCrO4 is L1 198 g/mole. a. 97.1 g b. 0.644g c. 194.2g @ e. 2.42x104g Barium hydroxide [Ba(OH)2] 1s a strong base Calculate the pH of a 0 00050 M Ba OH)2 solution foil“; '47 2X 0005’) a. —3.00 b. +3.00 0. +7.00 d. —11.00 e. +1100 . ‘ fH'» // Your shampoo bottle at home reads pH balanced at H: 6 25 What IS the [0H] concentration? '(I 5 ’ 4’5 a. 6.25 b. 7.75 0. 5.621110” d. 1.78X10‘ What volume of oxygen gas, at STP will be required to react completely with 72.5 g of acegrlenegfl ga ’21332 jfiTdnbg‘yr’) tjflflMbalanced equation? 2 C2H2 (g) 5 02 (g) —> 4 (g) + 2 H20 (1) (balanced equation) a. 62.5L’ b. 31.2L c. 312L (1. 156L 1 e. 453OL What is 9» when the photon energy is 4.567 x 1049.]? E = hv and c = 7w Where c = 2.9999 x 108 mfs and h= 6.626 x 10'34 J's 6. 6.2511106 21% saga :L 11m aw. 613160;»: a C ‘2); AC 7; s 2“ ,, %_c_._::(;. .124. we” “£32076 :. 655W; ' Short answer. Provide an answer to each question below. Work Required for Credit (50 points total) 11. You have a bottle of benzene (C6116), which you use for a solvent, in the laboratory refrigerator. If the bottle contains 127 mL of benzene, starting at 20°C, what if the final temperature if you add 87.5 kJ 0 energy to the benzene? (9 points) Q27." L)[/'/Ef%‘) 3', /é3>f /7’y 1", 2. [5 mo/ Freezing point benzene = 49°C, boiling point = 107 .7°C, Hf = 117 8 kJ/mol, H, = 12.9 kJémol, s (solid) = 3.68 J/(g—°C), 5 (liquid) = 5.23 J/(g—°C), s (gas) = 4.12 J/(g-°C), Kf: 5.12 °C/m/ 0(9)le 2/, ZZf/mb rartr ”’JLL 357' /o?.7‘c 12) Discuss the types of intermolecular forces in solutions and how they relate to colligative effects. Fifty (50) words'or less, plus any charts or drawings you want. (7 points) ZOnXM “pyb/If ”DI/'0LL % ihL’ 0’14;le CD wn—DVML GD _ TzhHI/‘mOlecuan 5V“) TWA/MM, efié’UL @ 3 13) A gaseous hydrocarbon is combusted, and from the carbon dioxide and water generated, determined to have ' 85.63% C and 14.37% H by mass. The mass of 258.1 mL of the gas, measured at STP, was found to be 0.6459 g. What is the molecular formula? (7 points) (,zW/z. £27730): 0.0][5Lm4 @ m ,2; WM. 5% (9. mm M“ w .. £6.0é . ,ch T/r‘7oo (L: .‘7’1 ,mrh‘ F- WWI-W 9 ‘3 V I 00. 14) A balloon filled with hydrogen gas starts With the following characteristics: volume = '1,000 L, pressure = 1.02 atm, temperature = 235°C. The balloon is released and rises for‘ZS minutes, getting to 1200 meters altitude, where the pressure is torr, and the temperature is —23"-’C. The balloon has a small leak? which released of hydrogen per min te. What is the final massof hydrogen and what is t 211 volume of the balloon? (9 pom s 0‘ 20‘ 5A 3 a, 1/3 n gr ,, (1.?0X.0/’206)(x6’o.3 ’F (2%“) Final Mass of Hydrogen: 7 . Final Volumeiof Balloon: 15) A solution of 12. 92 g of an unknown compound in 137.0 g of benzene (C6116) has a freezing point of , 5 006°C. The freezing point for pure benzene IS 5.45 5°C and the Kf for benzene IS 5 120°C/m What IS the nglar mass of the unknown compoun d©points) (agave/Q Al/lfim 0W‘IC ,_ ' ATfioWO/fi ”73/7: 3 WIN? (//~ fltol’gk’mm /Ji~:X lifl/t;5)c—M/20/m/)<@ I K73 ,2 ml CD 0.0/10, ”10/ i/gflo/ Molarmaggfl O /fi%mol 16) What volume of concentrated nitric acid (65.7% HNO3 by mass; d = 1.36 g/mL) must be dissolved in water to prepare 1000 L of a solution having a pH = 2.355? (10 points) Hint: Like the prpt/zlem 1n the qui©1 s is triple threat- a concentrfiw unit change, a pH problem and a dilution problem! 6'?» ”NO; L“: I!!!" lommtloih)( i771“! "N03 :1 ”/2 HMO) C‘ [ii/j (0:303 Win) A: WX l/ fOiV) i031 (gill/W3) I M C CW] 1‘“ L/ 4.2m I? M; V1: [1000 L 0 (D DCCDVL ; 4.91m /o’3MX/.ooo L) : 0. §// ML 2/” (/1: 0‘ (/1; Answer: 0,311 17) Extra Credit (7 points) ' (n+0 You bubble 30.0 mL of hydrogen gas at 220°C and 0.975 atm 1W a 275 mL solution of 6.01 x 10'2 M AUC13. What is the theoretical pH of the solution after the reaction? Ifyou measure the actual pH after the reaction and find it to be pH = 2.357 , what was the percent yield of the reaction? re 4 HO! 3+5 MAMA} 74“ r 10%;.235? 30mm, ”275 {L l, 2293‘?» N 0. " x W (0-W5W) '0’700”) :: moo/Zl/flo/ It; ’I ? fr 3 Coftoé) ‘Z‘ié’to/C) Percent yield: 57x02 ,7 MILE/7 woe?) 9 50.70 FIWY/O ...
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