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Unformatted text preview: Chem101 (Bontems, Fall 2009, TTH) Exam 3 Name: ____Key______________________ Multiple Choice – In the blank, write the letter of the best answer. You may show your work for partial credit when calculations are required. (3 pts. ea.) 1 ._B_______ The reaction of 2A + 3B C has a ∆H of ‐10.0 kJ. The ∆H for 2C 4A + 6B is: a. + 10 kJ c. ‐10 kJ b. +20 kJ d. ‐20 kJ e. none of these 2. C________ How many unpaired electrons are there in a carbon atom? a.
0 d. 6 b.
1 e. none of these c.
2 3._D_______ If you burned 2.20 g Mg with excess oxygen and obtained a q = ‐54,500 J, calculate ∆H for the combustion of a mol of magnesium in kJ is: a. ‐4.93 kJ c. ‐218 kJ b. ‐54.5 kJ d. ‐602 kJ 4._B_______If an atom has the electron configuration 1s22s22p3, how many more electrons does it need to fill its shell? a. 0 c. 6 b. 3 d. 8 5._B_______A reaction gives off 100 kJ of heat and does 25 kJ of work on the surroundings. The change in energy for this reaction is: a. b. 125 kJ ‐125 kJ c. d. 75 kJ ‐75 kJ 6._C_______Which of the following will reach the highest T when 10 kJ of heat are added to each? a. aluminum (specific heat = 0.903) b. iron (specific heat = 0.449) c. copper (specific heat = 0.385) d. All will have the same T because the same amount of heat was added. 7. __A_____ How much heat must be added to 50.0 g of water (4.18 J/g°C) to raise the temperature from 20.00°C to 30.00°C? a. 2090 J c. 120. J b. 41.8 J d. none of these 8. _C______ Given the following reaction information, calculate ∆H for reacting 10.0 g of ammonia with excess oxygen. 4NH3 + 5O2 4NO + 6H2O ∆H = ‐902.0 kJ a. ‐90.2. kJ d. ‐22.6 b. ‐361 kJ e. none of these c. ‐133 kJ 2 9. _B______ Which is true of Photon X (λ = 750 nm) and Photon Y (λ = 650 nm)? a. Y has higher frequency and lower E. b. Y has higher frequency and higher E. c. Y has lower frequency and lower E. d. Y has lower frequency and higher E.. 10. _D______ Of the following transitions in the Bohr hydrogen atom, the ______ transition results in the absorption of the highest energy photon. a. n= 5 → n = 1 d. n=1 → n=5 b. n = 6 → n = 4 e. n = 1 → n =4 c. n = 3 → n = 2 11. _C______ The _______ quantum number defines the shape of an orbital a. n c. l d. ms b. ml 12. _E______ Which of the following values is not a valid value for m of an electron in a 5d subshell? a. 1 c. ‐2 b. ‐1 d. 0 e. all of these are valid 13. _A______ The _______ subshell contains 5 orbitals. a. 4d c. 5s b. 5p d. 6f e. none of these 14. _E______ Each f‐subshell can accommodate a maximum of ___ electrons. a. 2 c. 6 b. 3 d. 10 e. none of these 15. _D_______ Which of the following quantum numbers represents an s orbital? c. n = 3, = 1, m = 0 a. n = 4, = 3, m = 1 d. none of these b. n = 3, = 2, m = 1 16. __B_____ What is the maximum number of electrons with ms = +½ that can be in the n = 2 shell of an atom? a. 1 d. 18 b. 4 e. none of these c. 9 17. __C______ Which set of quantum numbers is not allowed? a. n = 3, = 0, m = 0, ms = + ½ b. n = 3, = 2, m = 1, ms = ‐ ½ c. n = 1, = 1, m = ‐1, ms = ‐ ½ d. n = 2, = 1 , m = ‐1, ms = + ½ 18. Write a full electron configuration for carbon. (3 pts) 1s22s22p2 3 19. Write condensed configurations for each of the following: (6 pts) Mo (#42) [Kr]5s14d5 Hg (#80) [Xe]6s24f145d10 20. Both vanadium (V #23) and V+3 are paramagnetic. Draw orbital diagrams from [Ar] on for each of these and explain why they are paramagnetic. Be sure to define paramagnetic. (5 pts) V [Ar]4s23d3 ↑↓ ↑ ↑ ↑ _ ___ (These should be boxes, not just underlines.) V [Ar]3d2 ↑ ↑ ___ _ ___ Both have unpaired electrons so both are paramagnetic = attracted to a magnet. 21. Which element has the configuration [Kr]5s2? ___Sr____ (3 pts) 22. Which is larger and why? (6 pts) ‐1 F or Ne F‐1 is larger. They have the same 10 e‐, but Ne has more protons pulling in on the same shells of electrons. Na or K K is larger because it has one more entire shell of electrons. 23. Which has higher first ionization energy, Na or Rb? (6 pts) Na For Na, write the first three chemical equations representing ionization energy. Na Na+ + 1e‐ Na+ Na2+ + 1e‐ Highest increase Na2+ Na3+ + 1e‐ Where will you find the largest increase in the above series and why? See above. Because at this step you are taking the first inner shell e‐ ‐ destroying a stable noble gas configuration. 24. Calculate the final temperature of 25.0 g of silver (Cs = 0.235 J/g°C) initially at 27.0 °C after you add 2.35 kJ of heat. (5 pts) Tf = 427°C 4 25. Write a balanced equation representing the heat of formation of silver carbonate. (3 pts) 2Ag(s) + C(s) + 3/2 O2 (g) Ag2CO3 (s) 26. What mass of CO2 (44.0 g/mol) would be produced when you use 4,000.0 kJ of heat to warm a room by burning propane (C3H8)? C3H8 + 5O2 3CO2 + 4 H2O ∆H = ‐2217 kJ (5 pts) 238 g CO2 27. Calculate the mass of hot copper at 99.0°C needed to heat a cup of 120.0 g of cold coffee at 30.0°C to a better drinking temperature of 60.0°C, given that the specific heat of coffee is close to 4.18 J/g°C and copper is 0.385 J/g°C. This experiment was done in a coffee‐cup! (5 pts) M = 1.00 x 103 g 28. Find the enthalpy change, ∆H, for this reaction given the following information. Show your work. (4 pts) Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2 ∆H (kJ) (a) 2Fe(s) + 3 2O2(g) Fe2O3(s) ‐824.2 ‐282.7 (b) CO(g) + ½ O2 (g) CO2(g) ‐29.3 kJ Bonus: Describe the white solid demo that smelled like ammonia, the hydrogen balloon demo, the alkalai metal video clip and fluorescent bulb demonstrations. Include what you saw and the science behind the demo. ...
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This note was uploaded on 11/08/2011 for the course CH 101 taught by Professor Susanbontems during the Fall '11 term at Montgomery College.
- Fall '11