CHM134 General Chemistry I Exam I, Fall 2007 Dr. Steel Name SOLUTIONS Section 1: Multiple Choice. Circle the choice that is the best answer to each question. Each question in this section is worth 2 points. 1. Which one of the following is a homogeneous mixture? a) baked beans b) sugar dissolved in water c) chocolate chip ice cream d) chicken noodle soup e) a jar of chunky peanut butter 2. Which statement concerning solid NaCl is true? a) NaCl is a chemical compound. b) NaCl is a homogeneous mixture. c) NaCl is a heterogeneous mixture. d) The percentage of Cl in NaCl is dependent on where the sample is obtained. e) NaCl has properties similar to it component elements, sodium metal and chlorine gas. 3. The density of acetic acid is 1.05 g/ml. What is the volume of 327 g of acetic acid? a) 2.91 10-3 ml b) 3.21 10-3 ml c) 2.62 10 2 ml d) 3.11 10 2 ml e) 3.43 10 2 ml 4. A cube of iron has a mass of 29.31 g. If each side of the cube has dimensions of 1.55 cm, what is the density of iron? a) 0.127 g/cm 3 b) 5.92 g/cm 3 c) 7.87 g/cm 3 d) 12.2 g/cm 3 e) 18.9 g/cm 3 5. The temperature required to melt NaCl is 528 ºC. What is this temperature in kelvin? a) 231 K b) 255 K c) 528 K d) 801 K e) 977 K 6. Which one of the following is not a SI base unit? a) kilogram b) Fahrenheit c) kelvin d) meter e) second 7. Which of the following particles will not be deflected by charged plates? a) γ particles b) β particles c) α particles d) protons e) α and β particles
8. Alpha particles (α) are a) identical to electrons. b) high energy electromagnetic radiation. c) helium nuclei. d) identical to canal rays. e) positively charged electrons. 9. Which one of the following is an example of physical change? a) the evaporation of water b) the rusting of iron c) the combustion of hydrogen d) the tarnishing of silver e) both the rusting of iron and the tarnishing of silver 10. Which of the following are chemical properties of iodine? 1. Iodine is a purple solid at 25 ºC. 2. Iodine reacts with sodium metal to form sodium iodide. 3. The density of iodine is 4.93 g/cm 3. a) 1 only b) 2 only c) 3 only d) 1 and 3 11. Which of the following atoms contains the largest number of protons? a) 231 Pa b) 227 Ac c) 232 Th d) 226 Ra e) 222 Rn 12. Which of the following atoms contains the largest number of neutrons? a) 15P 31 b) 30 14 Si c) 37 17 32 34 Cl d) 16S e) S 16 13. Give the mass number of a bromine atom with 46 neutrons. a) 11 b) 35 c) 46 d) 80 e) 81 14. All of the following statements are true EXCEPT a) for any neutral element, the number of protons and electrons are equal. b) electrons and protons have equal mass, but opposite charges. c) the mass number is the sum of the number of protons and neutrons. d) the atomic number equals the number of protons. e) isotopes of an element have identical atomic numbers. 15. You have 4.15 g of each of the following elements: Ca, Cu, Ce, Cs, Cf. Which sample contains the largest number of atoms? a) Ca b) Cu c) Ce d) Cs e) Cf
16. Calculate the number of moles in 39 g silicon. a) 9.1 10-4 mol b) 0.72 mol c) 1.4 mol d) 11 mol e) 1.1 10 3 mol 17. What is the correct answer to the following expression: (72.61 68.59) 18.76? a) 7 10 1 b) 75 c) 75.4 d) 74.542 e) 75.5415 18. What is the correct answer to the following expression: (18 + 95) 0.077351? a) 8.7 b) 8.74 c) 8.741 d) 8.7407 e) 8.74066 19. Whose experimental work led to the conclusion that atoms are mostly empty space? a) Democritus b) Dalton c) Curie d) Rutherford e) Einstein 20. The molar mass of silver is 107.9 g/mol. What is the mass of a single silver atom? a) 1.539 10-26 g b) 1.792 10-22 g c) 1.079 10-20 g d) 1.901 10-18 g e) 5.581 10 21 g 21. The density of lithium is 0.546 g/cm 3. What volume is occupied by 1.96 10 23 atoms of lithium? a) 0.0859 cm 3 b) 0.596 cm 3 c) 4.14 cm 3 d) 5.63 cm 3 e) 39.0 cm 3 22. Which three elements are likely to have similar chemical and physical properties? a) sodium, lithium, and potassium b) sodium, magnesium, and aluminum c) nitrogen, oxygen, and neon d) nickel, copper, and zinc e) uranium, plutonium, and americium 23. What model of the atom was developed after J.J. Thomson discovered the electron? a) hardsphere b) plum pudding c) space-filling d) electron cloud e) none of the above
24. How many oxygen atoms are in 1.50 mol of SO 3? a) 7.7110 21 atoms b) 1.1210 22 atoms c) 3.0110 22 atoms d) 9.0310 23 atoms e) 2.7110 24 atoms 25. If 1.00 g of an unknown molecular compound contains 4.5510 21 molecules, what is its molar mass? a) 44.0 g/mol b) 66.4 g/mol c) 72.1 g/mol d) 98.1 g/mol e) 132 g/mol Section II: Solve each problem. Show your work in order to receive full credit. Each question in this section is worth 6 points. 26. A 2.000-kg sample of ore is known to be 83.2% iron by weight. How many iron atoms are in the sample? 1000 g 0.832(2.00 kg) 1kg = 1664 g Fe 1664 g Fe 1mol Fe 55.85 g Fe 23 6.022 10 atoms Fe 1mol Fe = 1.79 10 25 atoms Fe 27. An element consists of two isotopes. The abundance of one isotope is 95.72% and its atomic mass is 114.9041 u. The atomic mass of the second isotope is 112.9043 u. What is the weighted average atomic mass of the element? 0.9572(114.9041amu) + 0.0428(112.9043 amu) = weighted 114.8185 amu = 114.82 amu = average mass
28. Silicon dioxide, SiO 2, is found in many forms one of the more common ones is quartz. How many atoms of oxygen are in a 41.62-g quartz stone? 41.62 g SiO 1mol SiO2 60.09 g SiO 2 mol O 1mol SiO 23 6.022 10 atoms O = 8.342 1mol O 2 2 2 10 23 atoms O 29. Determine the percent composition of each element in chromium (III) sulfate tetrahydrate, Cr 2 (SO 4 ) 3 4H 2 O. Molar Mass of Cr 2 (SO 4 ) 3 4H 2 O = 2(52.00 g) Cr : 100% = 22.4% 3(32.07 g) S : 100% = 20.7% 16(16.00 g) O : 100% = 55.1% 8(1.008 g) H : 100% = 1.7% 30. If the fuel efficiency of an automobile is 27.0 miles per gallon, what is its fuel efficiency in kilometers per liter? (1 km = 0.621 mile, 1.000 L = 1.057 quarts, 4 quarts = 1 gallon) mi 1km 1gal 1.057 qt 27.0 = 11.5 gal 0.621 mi 4 qt 1L km L
31. Complete the table below. Each blank is worth 1 point. Symbol/Formula N 2 O 4 Pb(SO 4 ) 2 Cr SO 3 SnCl 2 Co NO Al(OH) 3 Na 2 SO 3 S 4 Cl 10 Ba Zr CuO K 3 PO 4 S NiBr 2 SrF 2 AgNO 3 BrF 5 Ca(ClO) 2 Name dinitrogen tetraoxide lead (IV) sulfate chromium sulfur trioxide tin (II) chloride cobalt nitrogen monoxide aluminum hydroxide sodium sulfite tetrasulfur decachloride barium zirconium copper (II) oxide potassium phosphate sulfur nickel (II) bromide strontium fluoride silver nitrate bromine pentafluoride calcium hypochlorite