Exam 2D KEY

Exam 2D KEY - Name . (please print as name appears on UNC...

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Unformatted text preview: Name . (please print as name appears on UNC roll) Chemistry 101 Section 1 Seat rowl# _ Exam 2D, October 20, 2010 _..—..— M Directions: 1. Print your name on the first and last pages of the exam. 2. For multiple-choice problems, write your answer (A. B, C, D, E) in the box provided on last page of exam. 3. On numerical problems, show your work including units as you go in order to receive credit for your work and write your answer in the boxlline provided (include units). 4. Make sure your significant figures are correct. 5. Use pen or pencil, but only exams written in pen can be regraded. W Honor pledge: l have neither given nor received help on this exam. Signed Worksheet D(H20) = 1.00 g/mL s(H20) = 4.184 Jig K 1 mL = 1 cm3 K = °C + 273.15 q=CAT AH = in AHfiproducts) - Zm AHf(reactants) c=)\v h=6.626x10‘34Js E=hv c=3.00x108m/s A = hlmv RH = 1.097 x107lm 135:4:an Lia—J; =—2.18x10'18J iz—iz nf n. n, n. Name 6 "' (please print as name appears on UNC roll) Questions 1-5 (5 pts each): 1. Which combination will produce a precipitate? A) NaCH3000(aq) and CaCl2(aq) B) KCl(aq) and Mg(N03)2(aq) C) NaOH(aq) and HCl(aq) D KCl(aq) and Ba(NO a E) A can Ac‘gfs3 2. What is the moiarity of an H2804 solution if 28.2 mL of a 0.559 M NaOH solution is required to neutralize a 25.0 mL sample of the H2504? A) 0.801 B) 0.200 . QMaOl—H- H2504, ———-—-‘9 N01290:; + ZHZO basalraanmumoil! [mi “2803‘ l I, amuaou‘ 00m. 3. Given the following reactions: 2NO-)N2+02 AH=-180.kJ 2NO+Oz—)2N02 AH=-112kJ what is the enthalpy of the reaction of nitrogen with oxygen to produce nitrogen dioxide, as shown below? N2+202->2N02 AH=? WCD Nz+oz——-" 2m +l80. ) i921] W 9364‘03"? 2M0; "HZ E) —224kJ +(08' 4. If the de Broglie wavelength of an electron is 1020 nm. what is its velocity? The mass of an electron is 9.11 x 10‘23 9. (W v= 03‘ Wt “ C) 8.11 x104mls D) 6.80 x105 mls E) 3.09 x 109 mls Name D (please print as name appears on UNC roll) 5. Calculate AE for a process in which a gas gives off 42 J of heat and has 14 J of work done on it by the surroundings (i.e. the gas contracts)? ___ [ AME led + ‘l “13) -28 J C— J D) +42 J E) +56 J 6. (16 pts) The combustion of silane (SiH4, MM: 32.10) produces silicon dioxide and water: SiH4(g) + 2 02(9) —a Si02(s, quartz) + 2 H200) AH = - 1516.5 kJ A) An unknown amount of silane is burned in a bomb calorimeter that has a heat capacity of 225 JIK. The temperature of the calorimeter increases by 9.3 Celcius degrees. How many grams of silane were burned? “40+ %le = O nun“ - %col = w Coal AT= “- 22%) (@323) W U [ml Sit-Li . K lmol Sir-L, x= .OOl68Mol91'qu_ I 32.1% 98? ml B) Suppose the previous experiment was repeated but with the addition of 650 9 water in the bomb. What is the heat capacity of the water in this experiment? 52 S F cisteth C) Without doing calculations, predict whether the change in temperature for the assembly (calorimeter + water) is the same, more or less than it was in the first experiment? of”? AT/fwtmvrlLD mouldbc lgwtham wrpr Cal 019w. H10 (lat. as War Msowow v was com +0: WW de omiwtse o um W Name E (please print as name appears on UNC roll) 7. (12 pts) Given the following reaction and thermochemical information, answer the following questions: CaMg(C03)2(s) -) Ca0(s) + MgO(s) + 2 002(9) AH = +312 kJ A) Calculate the enthalpy change when 2.50 9 calcium magnesium carbonate is consumed. ' \b --9 Win! Blah) = X [mi 76759 le B) Is this reaction an exothermic reaction or an endothermic one? El 0) In a separate experiment, enough reactant is consumed such that 852 kJ heat also required. What is the mass of carbon dioxide is produced in this experiment? .6le z.— 862K) Miwz X WW2 _ were ml MKS.”— " 240-3 8. (10 pts) A solution is made by dissolving an unknown amount of sodium oxalate, Na20204, in enough water to make 250.0 mL solution. When a 12.00 mL sample of this is titrated, it requires 25.82 mL of 0.02140 M KMnO4(aq) to complete react, according to the reaction below. How many grams of Na2C204 were dissolved in the original 250.0 mL solution? The balanced net ionic equation is: 5 02042‘(aq) + 2 Mn04'(aq) + 16 H+(aq) —) 2 Mn2+(aq) + 8 H200) + 10 002(9) Name D (please print as name appears on UNC roll) 9. (6 pts) What mass of AICI3 (MM: 133.35) must be added to 235 mL of 0.181 M KCI to produce a solution with a concentration of 0.250 M Cl"? Assume no volume change. Wasp .lgimoiCl" -.-. .0429 MoiCi" l, med .265L‘.2somi0i' = .0988 mid" b we! (0688,0419) .owamicr‘ imoiA—ici mare/m" + Water . H01 10. (10 pts) Given the following balanced reaction: A) which substance is the reducing agent? B) which element is reduced? g C) what are the spectator ions? H: + 23 2 Fe(N03)3(aq) + 2 HCI(aq) —) 2 HN03(aq) + 2 Fe(N03)2(aq) + 012(9) 4— 3 -—| - 0 'l' 2' D 11. (5 pts) Write the balanced chemical reaction for which AH corresponds to the molar heat of formation, AHf, of solid barium acetate. Name D (please print as name appears on UNC roll) 12. (18 pts) Below are the n=1 through n=4 energy levels for the Bohr Model of the hydrogen atom. From left to right, draw and label arrows that identify the following transitions, within these four levels. A) the absorption ‘of radiation from the ground state to n=2 state B) the emission of radiation with the smallest wavelength. -= jma-lvAG n=4 n=3 (9) n: (A) ' n1 C) Calculate 9i. (in m) for the transition depicted in Part A. Ae= #213 Kiwi)“; 315) = +l.b§xlD'"U . 1.22M», A: W: WW, - D) In what region (UV; vis, IR) of the electromagnetic spectrum does the radiation in Part A occur? 122mm Ll V E) Calculate AE (in J) for the transition in Part B. at. '2 ..L.——..L AG ZIKMD’J(P 423 .L 00 “2.0% (D F) What is the total number of emission lines, considering only these four quantum d levels? 4’»? 3 3 --9 2. Z -—-7 l 4 ’72 3 '7 | 4w7i \ o: Name D (please print as name appears on UNC roll) Question Answer Question Answer - ossible ...
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This note was uploaded on 04/05/2012 for the course CHEM 101 taught by Professor Farahh during the Spring '02 term at UNC.

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Exam 2D KEY - Name . (please print as name appears on UNC...

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