Exam 2C KEY

Exam 2C KEY - Name Raise; ‘ w (please print as name...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Name Raise; ‘ w (please print as name appears on UNC roll) Chemistry 101 Section 1 Seat rowl# Exam £0ctober 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. 0n numerical problems, show your work including units as you go in order to receive credit for your work and write your answer in the box/line 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 glmL s(H20) = 4.184 Jig K 1 mL = 1 cm3 K = °C + 273.15 AE=q+w q=smAT q=CAT AH = in AHf(products) - Em AH;(reactants) c=Av h=6.626x10'34Js E=hv c=3.00x105m/s A = hlmv RH = 1.097 x107lm AE=—thH $73—2- =—2.18x10"81 iz—iz n! n. nf n1 1‘ Name-M (please print as name appears on UNC roll) Questions 1-5 (5 pts each): _ 1. If the de Broglie wavelength of an electron is 8.97 nm, what is its velocity? The mass of an electron is 9.11 x 10‘28 g. ‘ _ g) £73.10mls . V: L a (919% MD'WJ :s q . WA {4.11xio'3'kqx397 MO“ w.) . 0x10 mls E) 3.09 x109 m/s 2. Which combination will produce a precipitate? A) NaCH3000(aq) and NH4Cl(aq) B N03 2(a)) W )A gNo are grandmas Ainm) D) NaOH(aq) and HCl(aq) E) KCl(aq) and Ba(N03)2(aq) 3. Find AH (in kJ) for the reaction F ‘ .——> + + D [F3(g) + leg) -> He) 5 2 act given the following information: "a "‘ |F3(9) -> |F(g) + leg) delta H = +390 kJ [F3 4' F}. "" lFe -" 3% |F(g) + 2 F2(g) —> |F5(g) delta H = -745 kJ A) +1135 B +35 C) -355 E) 4135 4. Calculate A5 for a process in which a gas gives off 42 J of heat and does 14 J of work on the surroundin s (i.e. the gas expands)? __ 63$ -- 42. ‘4 -28 J _ '0) +28 J D) +42 J E) +56 J Name 0 (please print as name appears on UNC roll) 5. What is the molarity of an H2804 solution if 28.2 mL of a 0.355 M NaOH solution is required to neutralize a 25.0 mL sample of the H2804? ( Bi 0.20%) ZMDH' f HZSOW—A: 1002304 + 24-120 C) 0.400 3} 32:3 0231'— -%%Imol may lmoi if so i ' L— Zmol Mali . 029m 6. (12 pts) Given tire following reaction and thermochemical information, answer the following questions: NM 20.0(0 2 NaHSO4(s) —> 2 NaOH(s) + 2 302(9) + 02(9) AH = +826 kJ A) Calculate the enthalpy change when 12.50 g sodium hydrogen sulfate is reacted. R, m . [Dill moi K20 id = x 2m: 104'le + 43.0 H B) Is this reaction an exothermic reaction or an endothermic one? C) In a separate experiment, enough reactant is consumed such that 1552 kJ heat also required. What is the mass of sulfur dioxide is produced in this experiment? ‘6210 u I 1662 Id lml 902 Xmol 802 24! SO; X= 3.1-9 MolSOLW' [moi Name - 0 (please print as name appears on UNC roll) 7. (16 pts) Methylhydrazine (CHaNz, MM: 46.09) is used as a liquid rocket fuel. The combustion of methylhydrazine with oxygen produces N2(g), 002(9), and H200): 2 CH5N2(I) + 5 02(9) —» 2 N2(g) + 2 002(9) + 6 H200) delta H = 4299 RJ A) An unknown amount of methylhydrazine is burned in a bomb calorimeter that has a heat capacity of 220.0 JIK. The temperature of the calorimeter increases by 12.3 Celcius degrees. How many grams of methylhydrazine were burned? mm-t- cal=O Ob'm-r- - ca = - Cm 457" " 220-0—L02'3oc) °C (km/1: "2%(9 J '—' —-2.=?Déa is.) 42% id = «93% id Ml .X he! 55': fit. :4 “ram =.| OM MW 6'23 B) Suppose the previous experiment was repeated but with the addition of 550 9 water in the bomb. What is the heat capacity of the water in this experiment? 2300 «3/5 O n 9.” § 7!: L9 33 6"" Si O k.) \/ 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? Why? ATJliavcai—ruoww b: less Wamth Cal Mme. HLOOCéOsaMQI/Wowfwmlw amm ohm. watA—t/iakwauw meowmwwm Name 0 (please print as name appears on UNC roll) 8. (10 pts) Given the following balanced reaction: A) which substance is the reducing agent? “053 2: B) which element is reduced? J C) what are the spectator ions? (gt-{'1 23 I 2 HN03(aQ) + 2 Fe(N03)2(aCI) ‘" CI2(Q) 9 2 Fe(N03)3(aCI) “' 2 HCKGQ) {- 7, 0 +3 “I 9. (10 pts) A solution is made by dissolving an unknown amount of sodium oxalate, Na2C204, in enough water to make 2500 mL solution. When a 10.00 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 Na20204 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) lM 290.0 m: ' ‘33" WWI “42904 F . 26001.. [84.03 1» lmol N42620:, 10. (6 pts) What mass of MgClz (MM: 95.21) must be added to 235 mL of 0.201 M KCI to produce a solution with a concentration of 0.250 M Cl"? Assume no volume change. ma .zaaLW= . 0688 ml or“ r, “lg/wiser. .‘20llmol6l" = .0412 W 01" I, .Olllp wwl Cl’haotl .dllowiolCl'l lmlwgaaqazw = Mia—- Imol ‘ 6623 5 Name (please print as name appears on UNC roll) 11. (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 emission of radiation from n=3 to the ground state B) the absorption of radiation with the lowest frequency. = Wt} A6 n=4 n=3 n=2 n=1 C) Calculate AE (in J) for the transition depicted in Part A. AE‘ —- 248M049 {.L. .51.] . l” 3" *lfl‘txlDF‘E) l.eexlo"’m D) Calculate 7L (in m) for the transition in Part B. A6“; .- 9.18 x 10"?) __l__ .. 41:10am?) 64’ 3’ A“ W/AB= 1.88 xlD"’w. E) in what region (UV, vis, IR) of the electromagnetic spectrum does the radiation in Part B occur? @80va w ' F) What is the total number of emission lines, considering only these four quantum levels? .W’Alaa saw. 2—»: WW 4’72. 3-»?! " 4w“ 4- Name C :4 (please print as name appears on UNC roll) 12. (5 pts) Write the balanced chemical reaction for which AH corresponds to the molar heat of formation, AHf, of solid calcium acetate. m “[5. ...
View Full Document

This note was uploaded on 04/05/2012 for the course CHEM 101 taught by Professor Farahh during the Spring '02 term at UNC.

Page1 / 7

Exam 2C KEY - Name Raise; ‘ w (please print as name...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online