1 CHEM 1180 Fall 2013 Exam 1B 27 SEP 13 Name KEY Show your work for each problem to receive credit Guard your test and conduct yourself properly NO graphing calculators Be sure to put your name on the back as well The last page of the exam is periodic table for your use Be careful with significant figures 1 12 points A tower crane one used to build high rise steel structures must have a counterweight to prevent it from tipping The specifications of the counterweight are that is must weigh 265 kg and occupy no more than 30000 cm3 a Determine which of the metals in the table below could be used to make the counterweight Hint calculate the minimum density the counterweight can have if it weighs 265 kg and fits within the specified space 3 d g cm Cost g Ag 10 5 0 66 Al 2 70 0 05 Cd 8 65 0 06 Pb 11 3 0 19 Os 22 6 13 Ti 4 54 0 10 Zr 6 51 1 57 The minimum density of the counterweight is d m 265kg 103 g 8 83 g V 30000cm3 1kg cm3 Therefore only metals with a higher density will meet the specification Thus the only metals that would work would be Ag 10 5 g cm3 Pb 11 3 g cm3 or Os 22 6 g cm3 b Which of the metals would be the most cost effective choice to make the counterweight Between Ag Pb and Os Pb is the cheapest and the most toxic 2 8 points The largest lake in Nebraska is Lake McConaughy As of 25 SEP 13 the volume of the lake was 962 5 GL Calculate the volume of the lake in gallons 1 gallon 4 quarts 1 quart 32 oz 1 oz 29 6 mL 962 5GL 109 L 1mL 1oz 1quart 1gallon 3 2 54 1011 gallons 1GL 10 L 29 6mL 32oz 4 quarts 2 3 4 points Give clear examples of a homogeneous mixture and a heterogeneous mixture A homogeneous mixture is a solution Thus salt water soda pop brass air etc would be examples A heterogeneous mixture is an imperfectly blended mixture Examples are sand wood pizza fresh squeezed orange juice etc 4 4 points Give an example of a chemical change that would be found in kitchen Baking a cake frying an egg saut ing onions roasting meat etc 5 4 points The average atomic mass of tellurium is 127 60 amu If the mass of an atom in amu is approximately the sum of the number of protons and the number of neutrons in the nucleus give a clear yet simple explanation why the average atomic mass is not close to an integer value Naturally occurring tellurium is a mixture of isotopes therefore the average atomic mass can be something different than a integer 6 2 points Give the name and symbol for one alkali metal Li lithium Na sodium K potassium Rb rubidium Cs cesium Fr francium 7 2 points Give the name and symbol for a chalcogen O oxygen S sulfur Se selenium Te tellurium Po polonium 8 4 points One compound of phosphorus and fluorine has a fluorine phosphorus mass ratio of 1 84 Another compound can be made with fluorine phosphorus mass ratio of 3 07 Note the ratio of the mass ratios is 3 07 5 1 67 1 84 3 What fundamental law of chemistry is the above demonstrating The Law of Multiple Proportions 3 9 7 points Complete the following chart of p of n0 of e Ba 2 56 82 54 As3 33 42 36 Symbol 138 56 75 33 10 10 points A tanning bed emits light with a wavelength of approximately 360 nm What is the energy of the photon hitting the tanner s skin RH 2 179 10 18 J h 6 626 10 34 J s c 2 997 108 m s c 2 997 108 m s 8 325 360 10 9 s 1 9 1 J E h 6 626 10 34 J s 8 325 1014 s 1 1 0 1 6 1 5 5 s 4 1 0 1 c 11 4 points What do line spectra tell us about the nature of energy within an atom The atom has specific energies or in other words the energies within an atom are quantized 12 4 points What are the possible values of ml for an electron in the 6d subshell ml 2 1 0 1 2 13 6 points Write an abbreviated electron configuration for the Pt IV ion Kr 4f145d6 4 14 8 points Construct an orbital energy level diagram to show how the electrons are placed in an iron atom 16 6 points Why is the atomic radius cesium larger than the atomic radius of barium The valence electrons of both atoms are in the 6s subshell But the effective nuclear charge of cesium is less than that of barium therefore the 6s electrons are not as attracted and thus further from the nucleus 15 4 points Arrange the following atoms in terms of increasing first ionization energy Al Ga Ge Si Ga Ge Al Si 5 17 4 points Which of the following atoms is paramagnetic Ca Ne S Zn S is only element of the four with unpaired electrons therefore it is paramagnetic 18 4 points Based on periodic trends which of the elements should have the greatest malleability Cr Mo W Of the three tungsten is the most metallic therefore we would expect it to have the greatest malleability 19 4 points An unknown element M combines with oxygen to form a compound with the formula M2O5 When the same element combines with chlorine it forms a compound with the formula MCl3 Make a sensible guess about the identity of the element The element is most likely nitrogen phosphorus arsenic antimony or bismuth Bonus Which of the following atoms has lowest energy 3p subshell C Na Ni Se Te Tellurium has the greatest nuclear charge therefore its orbitals have the lowest energies