CHEM 1411SAMPLE eXAM 1

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Dec 6, 2023

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1 . Houston Community College System Chemistry 1411 EXAM # 1A The Periodic table of the Chemical Elements

2 CHEM 1411 Sample Exam #1A (1,2, and 3) 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 244.2 0 F. What is boiling point in degrees celsius? A. 167.7 0 C B. 153.4 0 C C. 117.8 0 C D. 103.7 0 C ____ 3. Which of the following expressed measurement 52,030.2 m in correct scientific notation? A. 5.20302x10 4 m B. 5.203x10 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. 4.65 g + 2.0 g + 19.6442 g = A. 26.2942 g B. 26.29 g C. 26 g D. 26.3 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, 35 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 0.250 mole common antiacid, calcium carbonate? A. 4.00x10 2 g B. 25.0 g C. 4.00x10 -2 g D. 2.50x10 -3 g

3 ____ 10. Which one of the following reactions is not balanced? A. 2C 6 H 6(l) + 15O 2(g) à 12CO 2(g) + 6H 2 O (g) B. B 2 O 3(s) + 6HF (l) à 2BF 3(g) + 3H 2 O (l) C. UO 2(g) + 4HF (l) à UF 4(s) + 4H 2 O (l) D. 2B 5 H 9(l) + 12O 2(g) à 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 4 ____14. 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. 1. 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) 2. 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=1.6094 km) ( 6 points) 3. 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 6.01521 7.50 7 Li 7.016003 92.50 4. Terphthalic acid , used in the production of polyester fibers and films, is composed of carbon, hydrogen, and oxygen. when 0.6943 g of acid is subjected to combustion analysis it produced 1.471 g CO 2 and 0.391 g H 2 O. What is its empirical and molecular formula if its molar mass is 172 g/mol. ( 8 points)

4 5. 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) à 2 Al 2 O 3(s) A mixture of 82.4 g of aluminum (M=26.98 g/mol) and 117.65 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. !" 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) à CO 2 (g) + CaCl 2 (aq) + H 2 O(l) (not balanced) #" 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)?

5 CHEM 1411 SAMPLE EXAM # 1A - KEY (1, 2, and 3) PART-I 1. B (pico = 10 -12 , 134 x 10 -12 m = 1.34 x 10 -10 m) 2. C C = 5/ 9(F-32) = 5/ 9(244.2 - 32) = 5/ 9(212.2) = 117.9 o C 3. A 4. D sum = 26.2942 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 1. 13.6 g 1 lb (2.54 cm) 3 ----------- x ------------ x ------------------ = 0.491 lb/ in 3 cm 3 454 g 1 in 3 2. 11.3 km 1 mi 3600 sec ------------- x ---------------- x ---------------- = 2.53 x 10 4 mi/hr sec 1.6094 km 1 hr 3. Ave. atomic wt. of Li = (7.50/100) (6.01521) + (92.50/100) (7.016003) = 6.95 a.m.u. 4. m c = (3/11) mCO 2 = (3/11)(1.471) = 0.4012 g , m H = (1/9) mH 2 O = (1/9) (0.391) = 0.0434 g m O = m - (m c + m H ) = 0.6943 - (0.4012 + 0.0434) = 0.2497 g C = 0.4012/12 = 0.0334 , 0.0334/0.01561 = 2.14 = 2 H = 0.0434/1 = 0.0434 , 0.0434/0.01561 = 2.78 = 3 O = 0.2497/16 = 0.01561 , 0.01561/0.01561 = 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

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afari File Edit View History Bookmarks Window Help www-awn.aleks.com alex Yahoo Search Results Yahoo Search Results ALEKS O STOICHIOMETRY Using the Avogad ro Number -23 g and a small airplane has a mass of 5000. kg. An aluminum atom has a mass of 4.48 x 10 Use this information to answer the questions below. Be sure your answers have the correct number of significant digits. What is the mass of 1 mole of aluminum atoms? x10 ? X How many moles of aluminum atoms have a mass equal to the mass of a small airplane? Expation Check 2019 McGraw- 80 AUG 19 II

Am I right? Calculate the mass percentage of water in the hydrate. Show the calculations. Sample 1 : 60.87% Mass of hydrate : 0.46g Mas of water : 0.28g Mass percentage of water in the hydrate = 0.28g/0.46g x 100 = 60.87% Sample 1 2 3 Calculations for sample 1 Mass of aluminum dish 1.24g 1.26g 1.24g - Mass of aluminum dish + Epsom salt 1.70g 1.94g 1.80g - Epsom salt, original (hydrated) mass 0.46g 0.68g 0.56g 1.70g – 1.24g = 0.46g Mass of aluminum dish + Epsom salt after heating 1.42g 1.62g 1.61g Epsom salt, heated (dehydrated) mass 0.18g 0.36g 0.37g 1.42g- 1.24g = 0.18g Mass of water 0.28g 0.32g 0.19g 0.46g – 0.18g = 0.28g Moles of magnesium sulfate 0.0015mol 0.0030mol 0.0031mol 0.18g x (1mol/120.37g)= 0.0015mol Moles of water 0.016mol 0.018mol 0.011mol 0.28g x (1mol/18.02g) = 0.016mol Ratio of moles water: moles of magnesium sulfate 32:3 18:3 11:3.1…

Consider this formula. Z. If z = 4.0 and y = 9.2, what is the value of x? Express your answer to the tenths place (i.e., one digit after the decimal point). X =

CHEMISTRY FOR ENGINEERS (UPVOTE WILL BE GIVEN. PLEASE WRITE THE COMPLETE SOLUTIONS LEGIBLY. NO LONG EXPLANATION NEEDED. ANSWER IN 4 DECIMAL PLACES. BOX THE FINAL ANSWER/S. The mass of the earth is 5.98 X 1024 kg. How many moles of gold would have this mass? How many moles of aluminum would have this mass?

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