CH1410 Practice Exam #3 (Katz) Sp2015

Transcription

1 H1410 Practice Eam #3 (Katz) p2015 ection 1 - Multiple hoice - Write the letter of the ET HIE in the space provided. 1. How many moles of H2 can be made from the complete reaction of 3.0 moles of l? Reaction: 2 l + 6 H 2 l3 + 3 H2 ) 3 moles ) 3.0 moles ) 4.5 moles ) 9.0 moles 2. How many moles of sodium metal are needed to make 3.6 moles of sodium chloride? ) 0.9 ) 7.2 ) 1.8 ) 3.6 Reaction: 2Na + 2 2Na 3. The of a reaction is 75.0 grams of product and the actual is 42.0g. What is the percent? ) 75.0 ) 56.0 ) 31.5 ) Given the balanced equation 2 + i i2 +, if you were to react 1 mole of 2 with 1 mole of i, which statement is TRUE? 3.0 mol l 3.6 mol Na 42 g 75 g ) The 2 is the reactant. ) The i is the reactant. ) The i2 is the reactant. ) You have equal stoichiometric amounts of reactants. 3 mol H2 2 mol l 2 mol Na 2 mol Na = 4.5 mol H2 = 3.6 mol Na 5. onsider the following reaction: 2 Mg Mg, H rn = kj alculate the amount of heat (in kj) associated with complete reaction of 4 moles of Mg. = 56% ) kj ) kj ) kj ) kj 4 mol Mg kj 2 mol Mg = kj

2 6. Which Lewis structure below correctly represents the compound formed between magnesium and sulfur? ) ) Mg ) Mg 2+ ) Mg+ Mg Mg+ 7. Lewis theory predicts that the formula for an ionic compound of fluorine and calcium is: ) af ) a2f ) af2 ) af3 8. When a nonmetal bonds with a nonmetal ) a molecular compound forms. ) a covalent bond is involved. ) electrons are shared. ) all of the above are true 9. What is the correct Lewis structure for 2? ) ) ) ) 10. The total number of electrons to be counted for the Lewis structure of the 3 molecule is ) 4 ) 8 ) 18 ) 24

3 11. The Lewis structure, ) N2 + ) N2 - ) N2 ) both N2 + and N2 - N represents 12. Lewis theory predicts that the formula for an ionic compound of barium and sulfur is: ) a ) a2 ) a2 ) a3 13. The central chlorine atom in the chlorate anion, 3 - is surrounded by ) two bonding pairs and two unshared pairs of electrons. ) one bonding pair and three unshared pairs of electrons. ) three bonding pairs and one unshared pair of electrons. ) two double bonds and no unshared pairs of electrons. 14. Which of the following compounds has resonance structures? ) H4 ) H2 ) NH3 ) What is the angle between electron groups in the trigonal planar electron geometry? ) 90 ) ) 120 ) What is the electron geometry if you have 4 electron groups around the center atom? ) linear ) trigonal planar ) tetrahedral ) trigonal bipyramidal

4 17. What is the molecular geometry if you have a double bond, a single bond and 1 lone pair around the central atom? ) bent ) linear ) tetrahedral ) trigonal pyramidal 18. The elements with the highest electronegativity values tend to be found in the: ) upper right-side of the periodic table. ) lower right-side of the periodic table. ) upper left-side of the periodic table. ) lower left-side of the periodic table. 19. Which molecule listed below has a polar covalent bond? ) Na ) H2 ) H2 ) all of the compounds 20. Which molecule listed below is a nonpolar molecule? ) 4 ) 2 ) H3 ) all of the compounds 21. How many kilojoules of heat are needed to completely vaporize grams of water at its boiling point? For water, ΔH vap = kj/mol ) ) ) ) g H2 1 mol H g H2 22. ompare a small pot of water that is boiling vigorously to a large pot of water that is boiling gently. Which statement is TRUE? ) The small pot is boiling at higher temperature than the large pot. ) The large pot is boiling at a higher temperature than the small pot. ) oth pots are boiling at the same temperature. ) The vapor pressure of the liquid is lower than the pressure above the pot in each case kj 1 mol H2 = kj

5 23. How much energy does it take to melt a g ice cube? For water, ΔH fus = 6.02 kj/mol ) 102 kj ) 108 kj ) 936 J ) 5.64 kj g H2 1 mol H g H kj 1 mol H2 24. Which intermolecular force is due to the formation of an temporary dipole? = 5.64 kj ) dispersion forces ) dipole-dipole forces ) hydrogen bonding ) none of the above 25. Which molecule below has hydrogen bonding capability? ) H 4 ) H ) H 2 ) H 3 H 2 H 26. Name the following alkane: ) 1,3-dimethylheane ) 4-methylheptane ) 2-propylpentane ) 1-methyl-1-propylbutane 27. Which of the following alkanes is 1,4,-dichloropentane? H 3 H 2 H 2 H H 2 H 2 H 3 H 3 ) H 3 H H 2 H 2 H 2 ) H 2 H 2 H 2 H 2 ) ) H 3 H 2 H 2 H 3 H 3 H H 2 H H Name the major functional group in the following compound: ) alcohol ) aldehyde H 3 H 2 H 3 ) ketone ) carboylic acid

6 ection 2 - nswer the following computational questions using the information provided. You must show a plan for your calculations, along with the conversion factors involved for full credit. Write your answer in the bo provided. 1. What is the reactant for the reaction below given that you start with 2.50 grams of and 2.50 grams of i2? (Molar masses:, 12.01; i2, 60.09) Reaction: + i2 i g 1 mol g 1 mol 2 1 mol = mol g i2 1 mol i g i2 1 mol 2 1 mol i2 = mol 2 2. How many moles of NH3 can ly be produced by the reaction of 2.00 g of N2 with 3.00 g H2? (Molar masses: N2, 28.02; H2, 2.02) Reaction: N2(g) + 3 H2(g) 2 NH3(g) 3.00 g H2 1 mol H g H2 2 mol NH3 3 mol H2 = mol NH g N2 1 mol N g N2 2 mol NH3 1 mol N2 = mol NH3

7 3. In the following reaction, if you start with 42.0 g of 2 and 99.9 g KH, which is the reactant? (Molar masses: 2, 44.01; KH, 56.11) Reaction: 2 + 2KH K23 + H g g KH 1 mol g 2 1 mol H2 1 mol 2 = mol H2 1 mol KH 1 mol H2 2 mol KH = mol H g KH 4. If you start with 15.5 g of Na2 and 12.1 g u4 and produce only 3.05 g of u, what is the percent of u for the following reaction? (Molar masses: Na2, 78.05; u, 95.62; u4, ) 15.5 g Na2 Reaction: Na2 + u4 Na24 + u 1 mol Na2 1 mol u g Na2 1 mol Na g u 1 mol u = 18.9 g u 12.1 g u4 1 mol u4 1 mol u g g u u4 1 mol u4 1 mol u = 7.34 g u 3.05 g 7.34 g 100% = 41.5%