1. The distance between carbon atoms in ethylene is 134 picometers. Which of the following express the distance in meters?

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1 CHEM 1411 Exam #1 (1,2, and 3) Name: Score Part I. Multiple choice questions. ( 4 points each) Direction- Please write your correct choice in space provide. 1. The distance between carbon atoms in ethylene is 134 picometers. Which of the following express the distance in meters? A. 1.34x10-13 m B. 1.34x10-10 m C. 1.34x10-7 m D. 1.34x10-6 m 2. Acetic acid boils at F. What is boiling point in degrees celsius? A C B C C C D C 3. Which of the following expressed measurement 52,030.2 m in correct scientific notation? A x10 4 m B x10 4 m C. 5.20x10 4 m D. 5.2x10 4 m 4. Select the answer with correct number of decimal places for the following sum g g g = A g B g C. 26 g D g 5. Which of the following is a non-metal? A. Li B. Be C. Os D. I 6. Bromine is the only non-metal that is liquid at room temperature. Consider the isotope bromine-81, Br. Select the combination which list the correct atomic number, neutron number, and mass number respectively. A. 35,46,81 B. 35,81,46 C. 81,46,35 D. 46,81,35 7. Which of the following name is correct for given chemical formula? A. I 2 O 5, iodine pentoxide B. LiNO 3, lithium nitrate C. PbO, lead(i) oxide D. H 2 SO4, hydrosulfuric acid 8. Which of the following chemical formula is not correct for given chemical name? A. ferric oxide, Fe 2 O 3 B. calcium hydroxide, Ca(OH) 2 C. tetrasulfur dinitride, S 4 N 2 D. potassium chlorite, KClO 3 9. What is the mass in grams of mole common antiacid, calcium carbonate? A. 4.00x10 2 g B g C. 4.00x10-2 g D. 2.50x10-3 g 1

2 10. Which one of the following reactions is not balanced? A. 2C 6 H 6(l) + 15O 2(g) 12CO 2(g) + 6H 2 O (g) B. B 2 O 3(s) + 6HF (l) 2BF 3(g) + 3H 2 O (l) C. UO 2(g) + 4HF (l) UF 4(s) + 4H 2 O (l) D. 2B 5 H 9(l) + 12O 2(g) 5B 2 O 3(s) + 9 H 2 O (g) 11. Which identification is INCORRECT for the element? A. Na, sodium B. S, sulfur C. P, potassium D. Zn, zinc 12. Which of the following is not a chemical change? A. burning coal B. making bread rise using baking soda C. boiling an egg D. boiling water 13. Which ion has a -1 charge? A. CO 3 B. HSO 3 C. NH 4 D. SO Which of the following is improperly labeled? A. Cu- transition metal B. Mg- alkaline earth metal C. Br- halogen D. U- noble gas 15. How many carbon atoms are in CH 3 -CH 2 -COO-CH 3 A. 1 B. 2 C. 3 D. 4 Part II. Show all your work for complete credit. 16. The density of mercury, the only metal to exist as liquid at room temperature, is 13.6 g/cm 3. What is the density in pounds per cubic inch (lb/in 3 )? ( 1 lb=454 g, 1 in =2.54 cm) ( 8 points) 17. The speed needed to scape the pull of earth, s gravity is 11.3 km/s. What is this speed in mi/hr? ( 1 mi= km) ( 6 points) 18. Lithium, is used in dry cells and storage batteries and in high temperature lubricants, it has two naturally occurring isotopes, 6 Li and 7 Li. Calculate the atomic mass of lithium. ( 8 points) isotopes isotopic mass(amu) abundance(%) 6 Li Li

3 19. Terphthalic acid, used in the production of polyester fibers and films, is composed of carbon, hydrogen, and oxygen. when g of acid is subjected to combustion analysis it produced g CO 2 and g H 2 O. What is its empirical and molecular formula if its molar mass is 172 g/mol. ( 8 points) 20. Aluminum reacts with oxygen to produce aluminum oxide which can be used as an absorbent, desiccant or catalyst for organic reactions. ( 10 points) 4 Al (s) + 3 O 2(g) 2 Al 2 O 3(s) A mixture of 82.4 g of aluminum (M=26.98 g/mol) and g of oxygen (M=32.00 g/mol) is allowed to react. a) Identify the limiting reactant. b) Calculate the mass of aluminum oxide formed. c) Determine the mass of the excess reactant present in the vessel when the reaction is complete. d) What is the percentage yield for the reaction if reaction mixture produce 120 g of aluminum oxide? Bonus question( 10 points)- show all your work. a) When 11.2 g CaCO 3 reacts with excess hydrochloric acid, as below, 4.61 g of CO 2 is produced. What is the percent yield of CO 2? Do not type the units with your answer. CaCO 3 (s) + 2 HCl(aq) CO 2 (g) + CaCl 2 (aq) + H 2 O(l) (not balanced) b) Calcium reacts with oxygen to make calcium oxide, CaO. What is the theoretical yield of CaO(s) that could be prepared from 7.63 g of Ca(s) and 2.56 g of O 2 (g)? 3

4 CHEM 1411 SAMPLE EXAM # 1 - KEY (1, 2, and 3) PART-I 1. B (pico = 10-12, 134 x m = 1.34 x m) 2. C C = 5/ 9(F-32) = 5/ 9( ) = 5/ 9(212.2) = o C 3. A 4. D sum = g, round off to the least number of decimal point (one), sum = 29.3 g 5. D 6. A 7. B LiNO 3 is Lithium nitrate 8. D potassium chlorate, KClO 3 9. B CaCO 3 = 1(40) + 1(12) + 3(16) = 100 g/ml 10. C 2H 2 O (l) 11. C P is the symbol for phosphorous 12. D boiling water is a phase change from liquid to vapor 13. B HSO 3 (bisulfite) 14. D Uranium is an inner transition metal 15. D four carbon atoms PART-II g 1 lb (2.54 cm) x x = lb/ in 3 cm g 1 in km 1 mi 3600 sec x x = 2.53 x 10 4 mi/hr sec km 1 hr 18. Ave. atomic wt. of Li = (7.50/100) ( ) + (92.50/100) ( ) = 6.95 a.m.u. 19. m c = (3/11) mco 2 = (3/11)(1.471) = g, m H = (1/9) mh 2 O = (1/9) (0.391) = g m O = m - (m c + m H ) = ( ) = g C = /12 = , / = 2.14 = 2 H = /1 = , / = 2.78 = 3 O = /16 = , / = 1 = 1 empirical formula is C 2 H 3 O = 2(12) + 3(1) + 1(16) = 43 X = ( 172/ 43) = 4, (C 2 H 3 O) 4 or C 8 H 12 O 4 4

5 20a) (4x27) g (3x32) g (2x102) g 4 Al + 3 O 2 2Al 2 O g g X g (82.4) (2) (102) Al 2 O 3 from Al = = g = 156 g 4 x 27 (117.65) (2) (102) Al 2 O 3 from O 2 = = g 3 x 32 So, Al produce smaller amount of Al 2 O 3. Al is the limiting reagent. b) 156 g Al 2 O 3 formed c) (4x27) g (3x32) g 4 Al + 3 O 2 2Al 2 O g X g (82.4) (3) (32) O 2 used up in the reaction = = 73.2 g 4 x 27 O 2 (excess) = g = 44.4 g 120 d) % yield = x 100 = 77% 156 BONUS QUESTION: a) CaCO 3 (s) + 2 HCl(aq) CO 2 (g) + CaCl 2 (aq) + H 2 O(l) (11.2 g, CaCO 3 ) x ( 1 mole CaCO 3 / 100 g Mwt. ) ( 1mole CO 2 /1 mole CaCO 3 ) (44 g CO 2 / 1 mole CO 2 ) = g CO 2 % yield = ( g, actual value / g, theoretical value) x 100 = 93.5 % b) 2 Ca + O 2 2 CaO (7.63 g Ca) (1 mol Ca / 40 g) ( 1 molo 2 /2 mol Ca) ( 32 g O 2 / 1 mol O 2 ) = g O g O 2 requried to react woth 7.63 g Ca. Since have only 2.56 g O 2 in the reaction, therefore O 2 is limiting reagent. (2.56 g, O 2 ) ( 1 mol / 32 g O 2 ) ( 2 mol CaO / 1 mol O 2 ) (56 g CaO / 1 mol CaO ) = 8.96 g CaO, theoretical value of CaO 5

Houston Community College System

. Houston Community College System Chemistry 1311 EXAM # 1A The Periodic table of the Chemical Elements 1 CHEM 1311 Sample Exam #1A (1,2, and 3) Part I. Multiple choice questions. ( 4 points each) Direction-