Chemistry 1411 Sample EXAM # 3 Chapters 6, 7, & 8 1 CHEM 1411 EXAM # 3 (Chapters 6, 7, & 8) Part (1) - Multiple Choice - (3 points each) ____1. How many kJ of heat must be removed from 1.0x103 g of water (heat capacity of 4.184 J /g.K) to lower the temperature from 18.0°C to 12.0°C? A. 2.5x10-2 kJ B. 1.4 kJ C. 4.2 kJ D. 25 kJ ____ 2. From the following heats of reaction, 2C (graphite) + H2 (g) C2H2 (g) ∆ H = 227 kJ/mole 6C (graphite) + 3H2 (g) C6H6 (l) ∆ H = 49 kJ/mole calculate the heat for the reaction 3C2H2 (g) C6H6 (l) A. 632 kJ/mole B. -632 kJ/mole C. -178 kJ/mole D. 178 kJ/mole ____3. The heat of combustion of fructose, C6H12O6, is -2812 kJ. Using the following information, f for fructose. C6H12O6 (s) + 6 O2(g) ∆ H°f ( CO2 ) = -393.5 KJ/mole A -210.3 kJ/mol 6 CO2(g) + 6 H2O (l) ∆ H°f (H2O) = - 285.83 KJ/mole B. 210.3 kJ/mol C. -1264 kJ/mol D. 1264 kJ/mol ____4. What is the kinetic energy in J and cal of a 45-g golf ball moving at 61 m/s? A. 168 J, 40 cal B. 84 J, 20 cal C. 84 J, 350 cal D. 84 kJ, 20 kcal ____5. Consider the combustion reaction of ethane gas, C2H6(g): C2H6(g) + 7/2O2(g) 2CO2(g) + 3H2O(g) , ∆ H = -1430 kJ What is the enthalpy change for the reverse reaction if whole number of coefficients are used? A. +1430 kJ B. -1430 kJ C. -2860 kJ D. +2860 kJ ____6. What is the frequency of radiation that has a wavelength of 0.589 pm? A. 1.96 x 10-21 s-1 B. 5.09 s-1 C. 5.09 x 108 s-1 ____ 7. Statement, electrons fill the orbital singlet, then double up is called…………. A. Aufba principle B. Hund's rule 2 D. 5.09 x 1020 s-1 C. Puali's exclusion principle D. none of these ____ 8. For n = 4, what are the possible values of l? A. 3, 2, 1 B. 4, 3, 2, 1 C. 3, 2, 1, 0 D. 4, 3, 2, 1, 0 ____ 9. What is the maximum number of electrons that can occupy the subshell 3d? A. 1 B. 3 C. 5 D. 10 ____10. Write the electron configuration for the atom Cu, using the appropriate noble-gas inner core for abbreviation. A. [Ar]4s23d10 B. [Ar]4s24d9 C. [Ar]4s13d10 D. [Kr]4s13d10 _____11. For a particular process q = - 17 kJ and w = 21 kJ. Which of the following statement is false? A. Heat flows from the system to the surroundings B. The system does work on the surroundings C. ∆E = + 4 kJ D. The process is exothermic E. None of the above is false _____12. Consider the reaction H2 (g) + (1/2) O2 (g) → H 2O (I) , ∆ H = - 286 kJ; which of the following is true? A. The reaction is exothermic B. The reaction is endothermic C. The enthalpy of the products is less than that of the reactants. D. Heat is absorbed by the system E. Both A and C are true _____13. How much heat is required to raise the temperature of a 6.21 g sample of iron from 25.0 oC to 79.8 oC? (specific heat of iron is 0.450 J /g . oC) A. 70.0 J B. 101 J C. 386 J D. 756 J E. 153 J ____14. Consider the following atoms and ions;which is(are) isoelectronic with Argon? I. Cl- II. Mg A. only I IV. K+ III. P B. I and IV C. Only IV V. Ce D. II,III, and V E. none of these ____15. Which of the following quantum number combinations is incorrect for an orbital designation? A. n = 2 , l = 0 C. n = 2 , l = 1 , m = -1 E. All incorrect B. n = 1 , l = 0 , m = 0 D. n = 2 , l = 0 , m = -1 , s = + ½ ____16. Which of the following frequencies corresponds to light with the longest wavelength? A. 3.00 × 1013 s-1 B. 4.12 × 105s-1 C. 8.50 × 1020 s-1 D. 9.12 × 1012 s-1 ____17. How many electrons in an atom can have the quantum numbers n=3, l=2? 3 E. 3.20 × 109 s-1 A. 2 B. 5 C. 10 D. 18 ____18. An element has the electron configuration [Kr] 5s2 4d10 . The element is a(n): A. non-metal D. transition element B. metalloid E. two of these E. 6 C. metal ____19. How many of the following electron configurations for the species in their ground state are correct? i. Ca: 1s22s22p63s23p64s2 ii. Mg: 1s22s22p63s1 iii. V: [Ar] 3s23d3 iv. As: [Ar] 4s23d104p3 v. P: 1s22s22p63p5 A. 1 B. 2 C. 3 D. 4 E. 5 _____ 20. Which one has the largest radius ? A. K+ C. Al 3+ B. K D. Na + E. Mg _____ 21. Which one is isoelectronic with Neon ? A. F- B. Al3+ C. Na + D. O2- E. all of these _____ 22. Which one of the following forms an ionic bond with Chlorine gas? A. C B. Mg C. P D. As E. S _____ 23. Which of the following is the electron configuration for the Cr3+ ? A. [Ar] 4s2 3d4 B. [Ar] 4s1 3d5 C. [Ar] 3d3 D. [Ar] 4s2 3d1 _____ 24. Arrange the following atoms in order of increasing atomic radius: A. N < K < As < Fr D. Fr < K < As < N B. N < As < K < Fr E. K < Fr < N < As E. none of these N, K, As, Fr C. As < K < N < Fr _____ 25. Which of the following groups contains no ionic compounds? A. HCN, NO2, Ca(NO3)2 B. PCl5, LiBr, Zn(OH)2 D. KOH, CaF2, NaNH2 E. CH2O, H2S, NH3 C. NaH, CCl4, SF4 _____ 26. The element with the greatest tendency to gain electrons is A. F B. At C. O D. N E. Bi _____ 27. The lattice energy for ionic crystals increases as the charge on the ions ___ and the size of the ions ___? A. increases, increases C. decreases, increases B. increases, decreases D. decreases, decreases 4 Part (II) - Show all your work. 1. A 44.0 g sample of an unknown metal at 99.0 oC was placed in a constant-pressure calorimeter of negligible heat capacity containing 80.0 mL water at 24.0 oC. The final temperature of the system was found to be 28.4 oC. Calculate the Specific heat of the metal if density of water is 1.00 g/ml. 2. From the following heats of reaction, I) N2(g) + 2O2(g) 2NO2(g) ∆H = +67.6 kJ II) 2NO(g) + O2(g) 2NO2(g) ∆H = 113.2 kJ calculate the heat of the reaction , N2(g) + O2(g) 2NO(g) 3. For the electronic transition from n = 3 to n = 5 in the hydrogen atom, calculate the energy, and wavelength (in nm). 4. Write electron and core configuration for Bromine atom and determine the total number of unpaired electrons. 5. Phosphorous pentachloride is used in the industrial preparation of many organic phosphorous compounds. Equation I shows its preparation from PCl3 and Cl2: (I) PCl3 (l) + Cl2(g) PCl5(s) Use equation II and III to calculate ∆Hrxs of equation I: P4 (s) + 6 Cl2 (g) 4 PCl3 (l) ∆H = 1280 KJ (III) P4 (s) + 10 Cl2 (g) 4 PCl5 (s) ∆H = 1774 KJ (II) 6. Calculate the wavelength and frequency of light that is emitted when an excited electron in the hydrogen atom falls from n=5 to n=2? 5 7. A 25.0 g piece of aluminum (which has a molar heat capacity of 24.03 J/ °C. mol) is heated 82.4 °C and dropped into a calorimeter containing water (specific heat capacity of water is 4.18 J/ g . oC) initially at 22.3 °C. The final temperature of the water is 24.9 °C. Calculate the mass of water in the calorimeter. 8. Consider the following standard heats of formation: P4O10(s) = -3110 kJ/mol H2O(l) = -286 kJ/mol H3PO4(s) = -1279 kJ/mol Calculate the change in enthalpy for the following process: P4O10(s) + 6H2O(l) 4H3PO4(s) 9. Write the ground state electron configurations (or core configurations) for the followings and determine the total number of unpaired electrons and magnetic properties (paramagnetic or diamagnetic) in each. a) Chromium (Cr) __________________________________________ ,________, _________ b) Zinc (Zn) ___________________________________________,________, _________ 10. Using Hess’s law of constant heat of summation and given: I) ∆H = 44.1 kJ H2O(l) H2O(g) II) CH3COCH3(l) + 4O2(g) 3CO2(g) + 3H2O(l) ∆H = 1787 kJ III) CH3COOH(l) + 2O2(g) 2CO2(g) + 2H2O(l) ∆ H = 835 kJ determine the enthalpy of reaction for CH3COCH3 (l) + 2 O2(g) CH3COOH(l) +CO2(g) + H2O(g) 6 CHEM 1411 EXAM # 3 (KEY) 1. q = m.s . ∆T = (1.0x103 g)(4.184 J/g.K)( 18.0 – 12.0 oC) = 25104 J = 25100 J /1000 = 25 kJ 2. B 3C2H2 (g) 6C (graphite) + 3H2 (g) Reaction I (3 x rev.) ∆ H = 3(-227) kJ/mol Reaction II (same) 6C (graphite) + 3H2 (g) C6H6 (l) ∆ H = 49 kJ/mole __________________________________________________________________________ Overall reaction 3C2H2 (g) C6H6 (l) ∆ H = -632 kJ/mol 3. C ∆ H = ∆ H°f (reactants0 - ∆ H°f (products) -2812 = [6(-285.83) + 6(-393.5)] – [ 6 (0) + ∆ H°f (fructose)] ∆ H°f (fructose)= -1264 kJ/mol K.E. = (mV2)/2 = (.045 kg )(61 m/s)2 / 2 = 84 J / 4.184 = 20 cal 4. B 5. D For reverse reaction with whole number -2x (∆ H) = -2( -1430 kJ) = + 2860 kJ ν = (c / λ ) = ( 3.00x108 m/s )/ 0.589x10-12 m ) = 5.09 x 1020 s-1 or Hz 6. D 7. B 8. C 9. D 10. C 11. C ( should be ΔE = +4 kJ) 12. E 13. E q = mc Δ T = (6.21 g)(0.450 J/g. oC)(79.8 oC –25.0 oC) = 153 g 14.B 15. D 16. B largest wavelength has smallest frequency 17. C ( l = 2 is d orbital with 10 electrons ) 18. E 19. B 20. B 26. A 21. E 27. B 22. B 23. C 24. B 25. E PART II 1. C∆T (metal) = C ∆T (water) ms ∆T (metal) = ms ∆T (water) (44.0)(smetal) (99.0-28.4) = (80.0)(4.184)(28.4 -24) smetal = 0.474 J/g.oC 2. N2 + 2O2 2NO2 2NO2 H= + 67.6 kJ 2NO + O2 H = + 113.2 kJ N2 + O2 2NO H = + 180.8 kJ 7 3. E = 2.18 x 10 18 ( 1/32 - 1/52 ) = 1.55 x 10 19 J E = hc/ ( 6.63 x 10 34 )( 3.00 x 108 ) = ------------------------------------------ = 1.28 x 106 m = 1280 nm ( 1.55 x 10 19 ) 4. 35Br = 1ss 2s2 2p6 3s2 3p6 4ss 3d10 4p5 = [ Ar ] 4ss 3d10 4p5 One unpaired electron 5. Rev x 1/4 (ii) 1/4 (iii) 1/4 P4 + 6/4 Cl2 PCl3 + Cl2 + 320 kJ ; H = 443.5 kJ 1/4 P4 + 10/4 Cl2 PCl5 PCl3 ;H= ; H = 123.5 kJ PCl5 6. hc/λ = 2.18x10 –18( 1/ni2 – 1/nf2) (6.63x10 –34)(3.00x108) /λ = 2.18x10 –18( 1/52 – 1/22) λ = 4.34x10 –7 m h ν = 2.18x10 –18( 1/ni2 – 1/nf2) (6.63x10 –34) ν = 2.18x10 –18( 1/52 – 1/22) ν = 6.91 x1014 sec -1 7. (mc Δt )Al = (mc Δt )water (25.5/27 )(24.03)(82.4-24.9) = m water (4.18)(24.9-22.3) m water = 118 g 8. Δ Hrx = ΔHf 0 (products) - ΔHf 0 (reactants) = [ 4(-1279)] – [ (-3110) – (6(-286)] Δ Hrx = -290 kJ 9. Cr : [Ar] 4s1 3d5 , 6 unpaired electrons , paramagnetic Zn :[Ar] 4s2 3d10 , 0 unpaired electrons, diamagnetic 10. ΔH = ΔH (I) + ΔH (II) + reverse ΔH (III) = (-441.1 ) + (-1787) + +835) = ΔH = -996 kJ 8
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