Name. Student ID # CHEMISTRY 121 [Tyvoll] PRACTICE EXAM III. November 23, Possibly Useful Information:

Transcription

1 Name Student ID # CHEMISTRY 121 [Tyvoll] PRACTICE EXAM III November 23, Possibly Useful Information: 1) ( ) ( ) ( ) ( ) ( X ) 1 atm = lb/in 2 = kpa 2) ( ) ( ) ( X ) ( ) ( ) 1 atm = 101,325 N/m 2 3) ( ) ( X ) ( ) ( ) ( ) 1 atm = 101,325 Pa = bar 4) ( ) ( X ) ( ) ( ) ( ) 1 atm = mb 1 atm = bar 5) ( ) ( ) ( ) ( X ) ( ) 1 mile = km 1 league = 2.60 miles 6) ( ) ( ) ( ) ( ) ( X ) R = L atm/mol K 7) ( ) ( X ) ( ) ( ) ( ) R = J K -1 N = x ) ( ) ( ) (X ) ( ) ( ) h = 6.63 x J s c =3.0 x10 8 m/s 9) ( ) ( ) (X ) ( ) ( ) 10) ( ) (X ) ( ) ( ) ( ) 11) (X ) ( ) ( ) ( ) ( ) 12) (X ) ( ) ( ) ( ) ( ) 13) (X ) ( ) ( ) ( ) ( ) 14) ( ) ( ) (X ) ( ) ( ) 15) ( ) ( ) ( ) ( ) (X ) Chemistry 121 (Tyvoll) PRACTICE EXAM III

2 November 23, 2004 Part I. Multiple Choice (3 points each -- Total points = 45.) Print your name in the space above and on the answer sheet. Choose the BEST answer for each of the following questions and blacken or mark an "X" in the correct space on the answer sheet. Good luck!! 1. What is the change in internal energy of a system that absorbs 635 J of heat and does 249 J of work? J J J J J 2. When heat is absorbed by the system from the surroundings, the process is said to be, and the sign of process is. 1. exothermic; positive 4. endothermic; negative 2. exothermic; negative 5. spontaneous; positive 3. endothermic; positive 3. What is the lowest-numbered principal shell in which s orbitals are found? Calculate the wavelength, in nanometers, of an electron moving at a speed of m/s. The mass of an electron is kg. (1 J = 1 kg m 2 s -1 ) nm nm nm nm nm 5. Calculate the energy, in kilojoules, of one mole of photons of yellow laser light of wavelength 570 nm An AM radio station operates at a frequency of 1080 khz. What is the wavelength, in meters, of the radio waves? Which word listed below best describes the energy levels of the 2p electrons in atomic nitrogen?

3 1. core 4. metalloid 2. degenerate 5. metallic 3. diamagnetic 8. Which of the following is the electron configuration of Ne? 1. 1s 2 2s 2 2p 5 3s s 2 2s 2 2p 5 3s 2 3p s 2 2s 2 2p 2 3s 2 3p 2 4s s 2 2s 2 2p 3 3s 2 3p s 2 2s 2 2p 6 9. In which list are all of the elements in the same group? 1. K, Ca, Sr 4. N, O, F 2. Ba, La, Hf 5. Ce, Pr, Nd 3. B, Ga, Tl 10. Which element has the greatest ionization energy? 1. Ge 3. Sn 2. Se 4. Te 11. Which of the following orbitals fills first? 1. 2p 4. 5p 2. 3p 5. More information is needed. 3. 3d 12. Which of the following is an s-block element? 1. Cs 4. Sm 2. Fe 5. Mo 3. O 13. Which of the following species would have the greatest attraction to a magnetic field? 1. Fe Fe Fe O 2-3. Fe Metallic character across a row and down a column of the Periodic Table. 1. increases; increases 3. decreases; increases 2. increases; decreases 4. decreases; decreases

4 15. In which atom do the outermost electrons experience the weakest effective nuclear charge? 1. N 4. F 2. C 5. Be 3. O Part II - Total points = 55. Answer each of the following questions. SHOW ALL WORK! 1. (5 points) An electron microscope relies on high-speed electrons to obtain images of what are normally sub-microscopic structures. What is the de Broglie wavelength (in Angstrom units, A) of electrons, moving at a speed of 4.05 x 10 6 m/s if the mass of an electron is assumed to be 9.11 x g? Show all work for credit! Planck s constant is x J s and 1 A = 1.00 x m. If atoms have atomic radii which range from about 0.37 (H) to 2.11 (Rb) Angstrom units, is the wavelength calculated above comparable to the size of atoms? explain why or why not. 2. (10 points) Nitric acid can be formed when NO 2, an air pollutant, reacts with water, where 3 NO 2 (g) + H 2 O(l) 2 HNO 3 (aq) + NO(g) Use the standard enthalpies of formation in the table below to calculate the enthalpy change for this reaction. Show all work for credit! Compound DH 0 f (kj/mol) NO(g) NO 2 (g) HNO 3 (aq) H 2 O(l) Is this reaction exothermic or endothermic? Does the reaction give off heat or absorb heat? You should explain your answers briefly but clearly. 3. (10 points) Use the following thermochemical equations C 2 H 5 OH(l) + 3 O 2 (g)? 2 CO 2 (g) + 3 H 2 O(l) H 2 (g) + 1/2 O 2 (g)? H 2 O(l) C(graphite) + O 2 (g)? CO 2 (g)?h = kj?h = -286 kj?h = -394 kj to calculate the enthalpy change for the reaction 2 C(graphite) + 3 H 2 (g) + 1/2 O 2 (g)? C 2 H 5 OH(l)?H =?

5 4. (10 points) (10 points) The atoms of an unknown element have the following electron configuration: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2 (a) How many electrons are there in a neutral atom of this element? (b) How many valence electrons are there in an atom of the element? (c) What is the element which has the electron configuration shown above? (d) What is the expected charge for the most stable ion for the element above? (e) The element above is a(n) (s-,p-,d-, or f-) block element. 5. (10 points) Fill in the blanks with the correct symbols for the elements. An atom that has a half-filled 2p subshell. An atom that has a total of 6 electrons in its n = 3 principal quantum shell. An atom that has a tendency to form a +2 cation with the same electron configuration as Ar (Z =18). The element that forms a monocation that is isoelectronic with Kr The period 2 element that has only 1 electron is its 2p subshell The element that forms a dianion (X 2- ) that is isoelectronic with Ne 6. (10 points) ) A 2.84 g sample of ethanol, C 2 H 5 OH (46.07 g/mol), was burned in an excess of oxygen in a bomb calorimeter. The temperature of the calorimeter and its contents rose from C to a final temperature of C. Calculate both q and H for the combustion of 1 mol of ethanol if the heat capacity (C) of the calorimeter and contents was 9.63 kj/ 0 C. Show all work for credit! C 2 H 5 OH(l) + O 2 (g) CO 2 (g) + H 2 O(l) (unbalanced) Is this reaction exothermic or endothermic? Does the reaction give off heat or absorb heat? You should explain your answers briefly but clearly.