Chemistry 105, Review Exercises for the Comprehensive Final Exam

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1 hemistry 105, Review Exercises for the omprehensive Final Exam omeclature 1. Provide the missing names and formulas for the following (answers at the end): a. i 3 (P 4 ) 2 b. chromium (III) sulfate c. l 4 d. 2 S 3 (name this as an acid) e. I (name this as an acid) f. perchloric acid g. a 2 2 ounting by weighing, empirical and molecular formulas 2. alculate the number of atoms in g of TT, 7 5 ( 2 ) 3 (molar mass 227. g). Ans x atoms 3. Dimethylhydrazine, the fuel used in the Apollo lunar descent modules, is made of carbon, hydrogen, and nitrogen atoms. The combustion of g of the material in oxygen gives g of 2 and g 2. What is the empirical formula? If the molar mass is g, what is the molecular formula? Ans Stoichiometry 4. For the following reaction 32.0 g of Al and 72.0 g of S react. 2Al + 3S Al 2 S 3 a. What's the theoretical yield of Al 2 S 3? Ans.89.1 g b. If the actual yield is 80.0 g what's the percent yield? Ans % 5. The following equation represents the reacton used to obtain Si from sand. Sand consists mostly of Si 2. Si Si a. ow many grams of are needed to react with g of Si 2? Ans g b. ow many grams of Si are produced? Ans g c. ow many moles of are produced? Ans moles Reactions in Solution and Solution Stoichiometry 6. Use the half reaction method to balance the following reaction in acid solution (answer at the end). r 2 7 +S 3 r +3 + S 4 7. Use the half reaction method to balance the following reactions is basic solution (answer at the end). Fe() 3 + r 3+ Fe() 2 + r 4 8. ow many milliliters of a M Al( 3 ) 3 solution are needed to furnish g of Al( 3 ) 3? Ans ml 9. ow many grams of ul 2 would be needed to prepare 500. ml of a 2.0 M solution? Ans g 10. ow many grams of ul 2 would be needed to prepare 1.00 L of a M l - solution? Ans g

2 11. What volume of M Ba( 3 ) 2 is required to react completely with 20.0 ml of 0.937M o 2 (S 4 ) 3? ow many grams of precipitate will form? Ans L g o 2 (S 4 ) 3 (aq) + 3Ba( 3 ) 2 (aq) 3BaS 4 (s) + 2o( 3 ) 3 (aq) 12. A solution of ml of M K is mixed with a solution of ml of M is 4. ow many grams of precipitate form? Molar mass for i() 2 = 92.7 g. Ans g 2K(aq) + is 4 (aq) K 2 S 4 (aq) + i() 2 (s) Gases 13. A 25.00L-flask has 1.35 mol of hydrogen gas at 25. o and a pressure of 1.05 atm. itrogen gas is added to the flask at the same temperature until the pressure rises to 1.64 atm. ow many moles of nitrogen gas are added? Ans moles 14. A balloon filled with helium has a volume of 1.28 x 10 3 L at sea level where the pressure is atm and temperature is 31.0 o. The balloon is taken to the top of a mountain where the pressure is atm and the temperature is o. What is the volume of the balloon at the top of the mountain? Ans x 10 3 L 15. Dinitrogen monoxide, also called nitrous oxide, is used as a propellant gas for whipped-cream dispensers. It is prepared by heating ammonium nitrate to 250. o. 4 3 (s) What volume of dinitrogen monoxide gas is formed at 250. o and 1.0 atm when 5.00 g of 4 3 is heated? Ans. 2.7 L 16. Methane burns in oxygen by the following reaction 4 (g) (g) 2 (g) (g) When 8.00 L of methane at 125. o and 1.00 atm is burned in an excess of oxygen, the products are collected into a separate 10.0-L flask. a. What is the total pressure of the products in the flask at 125. o? Ans atm b. What is the partial pressure of each of the products in the flask? Ans. P 2 = atm P 2 = 1.60 atm Electronic Structure and Periodicity 17. A photon of violet light has a wavelength of 423. nm. alculate: a. the frequency. Ans x s -1 b. the energy in joules per photon. Ans x J c. the energy in kilojoules per mole of photons. Ans KJ/mol 18. Write the ground state electron configuration and the abbreviated ground state electron configuration for each of the following. Also, indicate the number of unpaired electrons for each (answers at the end). a. P b. V c. Se 19. Which of the four atoms a, P, l or K (answers at the end) a. has the largest atomic radius? b. has the highest ionization energy? c. is the most electronegativity?

3 Bonding and Molecular Geometry 20. Using the periodic table classify the bonds in the following compounds as ionic or covalent. If covalent, classify the bond as polar or not (answers at the end). MgBr 2 F 4 Si 2 a 3 F Br 2 a 21. For the following (answers at the end): a. write the electron dot structure b. draw the D representation of the 3-D shape c. give the molecular geometry d. give the bond angle around the central atom e. indicate if the molecule is polar f. give the hybridization for each atom (except where indicated not to) S ( is the central atom) IBr 2 - (skip hybridization) Give the hybridization for each atom (except ) in the following organic solvent. Unshared electrons are not shown. ow many sigma and pi bonds are there (answers at the end)? Give the hybridization for the nitrogens and oxygens in the following. Unshared electrons are not shown. ow many sigma and pi bonds are there in each (answers at the end)? l Thermochemistry 24. ow many kilocalories are required to convert 250. g of ice at o to steam at o? Specific heats: ice 0.50 cal/g o, water 1.0 cal/g o vap = 540. cal/g fus = 79.7 cal/g Ans. 1.8 x 10 2 kcal 25. Fructose, , is a sugar commonly found in fruit. A 4.50 g sample of fructose is burned in a bomb calorimeter. The heat capacity of the calorimeter is x 10 4 J/ o. The temperature in the calorimeter rises from o to o. a. alculate the quantity of heat evolved. Ans kj b. alculate the heat of combustion per gram and per mole. Ans kj/g, x 10 3 kj/mole

4 26. When a 3.88 g sample of 4 3 (s) dissolves in 60.0 g of water in a coffee-cup calorimeter, the temperature drops from 23.0 o to 18.4 o. alculate for the solution process: 4 3 (s) 4 + (aq) (aq) Assume that the specific heat of the solution is the same as that of pure water (4.184 J/g o ). Ans kj 27. Given the following thermochemical equations, 2 2 (g) + 5/2 2 (g) 2 2 (g) + 2 (l) (s) + 2 (g) 2 (g) 2 (g) + 1/2 2 (g) 2 (l) = kj = kj = kj calculate the for the decomposition of one mole of acetylene to its elements in their stable state at 25 o and 1 atm. Ans kj 2 2 (g) 2(s) + 2 (g) 28. Using f o 's calculate o per mole of ammonia in the following reaction. Also, calculate o per gram of ammonia. Use the data in table 8.3 in your text book. Ans kj/mole, kj/g 4 3 (g) ammonia o f 's 3 (g) 2 (g) (g) 2 (g) (g) 4(g) (g) kj/mole You should know this one kj/mole kj/mole 29. alcium carbide, a 2, is the raw material for the production of acetylene (used in welding torches). alcium carbide is produced by reacting calcium oxide with carbon. arbon monoxide is also produced in this reaction. When one mole of calcium carbide is formed kj is absorbed. a. Write a thermochemical equation for this reaction. b. Is the reaction exothermic or endothermic? c. Draw and energy diagram for this reaction. d. What is when 1.00 g of a 2 (s) is formed? e. ow many grams of carbon must react to produce 3.03 x 10 3 kj of heat? Ans. a. a(s) + 3(s) a2(s) + (g) = kj b. endothermic d kj e g Answers 1. a. nickel (II) phosphate, b.r 2 (S 4 ) 3, c. carbon tetrachloride, d. sulfurous acid, e. hydroiodic acid, f. l 4 g. sodium peroxide r S 3 2r S Fe() 3 + r Fe() 2 + r a. P 1s 2 2s 2 2p 6 3s 2 3p 3 [e] 3s 2 3p 3 three unpaired b. V 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3 [Ar]4s 2 3d 3 three unpaired c. Se1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 4 [Ar]4s 2 3d 10 4p 4 two unpaired

5 19a. K b. l c. l 20. MgBr 2 ionic, F 4 polar covalent, Si 2 polar covalent, a 3 ionic between the a 2+ and the 3 but polar covalent between and, F polar covalent, Br 2 nonpolar covalent nonpolar polar polar nonpolar polar a polar ionic 21. S linear, 180 o, polar molecule, S sp 2, sp, sp 2 Br I Br linear, 180 o, nonpolar molecule - triginal planar, 120 o, nonpolar molecule, sp 2, = sp 2, - sp Both end s are sp 3, the middle is sp 2, is sp 2. There are 9 sigma bonds and 1 pi bond. 23. l - sp 3 sp 3 sp sp = sp 2 3σ 2π 1σ sp 3 sp 2 2π 2σ 3σ 1π