Chemistry 1A Fall 2010 Midterm Exam 1 September 15 2010 90 min closed book Name KEY SID GSI Name The test consists of 5 short answer questions and 18 multiple choice questions Put your written answers in the boxes provided Answers outside the boxes may not be considered in grading Write your name on every page of the exam Question Points 2 6 54 Anesthetics Short Answer 4 7 Mohs Short Answer 6 4 Nail Polish Short Answer 6 10 T K T C 273 15 75 1 atm 760 mm Hg 760 torr 1 bar Multiple Choice 1 18 Total Score Useful Equations and Constants Page PV nRT n2 P a 2 V nb nRT V KE 1 2 mv 2 Ptotal PA PB XAPtotal XBPtotal N0 6 02214 x 1023 mol 1 R 0 0821 L atm K 1 mol 1 Name GSI Airbags Experiment In the airbag lab you were challenged to generate the largest gas volume in a plastic bag by reacting baking soda NaHCO3 with acetic acid CH3COOH NaHCO3 s CH3COOH aq CH3COONa aq H2O l CO2 g A pair of students performed the following trials in building their airbags Moles of sodium Moles of acetic acid Moles of carbon Trial bicarbonate NaHCO3 CH3COOH dioxide CO2 A 0 012 mol 0 017 moles B 0 018 mol 0 017 moles C 0 018 mol 0 025 moles D 0 012 mol 0 025 moles 1 Which of the trials shown in the table produced the optimal GREEN airbag minimal unreacted starting material A 3 B 4 C D 2 CO2 g produced in the reaction of baking soda and acetic acid is collected in a 100 mL metal container What amount of CO2 g will fill the container to 5 atm at 300 K A 0 020 moles 2 B 100 mL C 0 020 grams D 20 moles 3 A sample of CO2 is sealed in a metal container at 300 K The pressure inside the container is 6 atm What is an estimate of the pressure inside the container if you cool the gas to 100 K At this temperature CO2 is a solid A 2 0 atm 2 B 1 8 atm C 1 0 atm 3 D 0 01 atm 4 4 Helium He and carbon dioxide CO2 gases are confined in identical containers The graph of P vs T for the gases is shown Why is the slope for the He larger than that for CO2 A The volume of He atoms is smaller B The temperature of He is larger C The volume of the container with the CO2 sample is smaller D There are fewer number of moles of CO2 4 5 Pressure atm He CO2 Temperature K Compare two samples of a gas Sample A A plastic baggie filled with 0 060 moles of N2 at 400 K Sample B A sealed container at 6 atm with 0 020 moles of CO2 at 300 K How do the average speeds of the gas molecules in Samples A and B compare A The average speed in Sample A is higher because the temperature is higher 3 B The average speed in Sample B is higher because the pressure is higher C The average speed in Sample A is higher because the number of moles of gas is greater D The average speed in Sample B is higher because the mass of the gas is higher Page 2 of 6 Name GSI General Anesthesia The molecules below all function as anesthetics to producing a state of unconsciousness that allows humans to tolerate surgery It is difficult to imagine surgery without these compounds Name Formula Structure Molar mass Boiling point xenon Xe nitrous oxide N2O chloroform 131 g mol 108 C 44 g mol 88 5 C CHCl3 119 g mol 61 C halothane CF3CHBrCl 197 g mol 50 C dimethyl ether CH3OCH3 46 g mol 23 6 C diethyl ether CH3CH2OCH2CH3 74 g mol 34 6 C 185 g mol 48 5 C isoflurane CF3CHClOCHF2 H H H C C H H O H H C C H H H 6 How many molecules with distinct properties have the overall chemical formula CHCl3 A 1 2 B 2 C 3 D 4 or more 7 Are the C O C atoms in dimethyl ether CH3OCH3 arranged in a straight line A Yes because there are two carbon atoms connected to oxygen B Yes because the molecule is symmetrical C Yes because the molecule satisfies the HONC1234 rule D No because the electronic shape around oxygen is tetrahedral 3 8 Which compound would you expect to have the largest value of a in the van der Waals equation A CHCl3 4 B CF3CHBrCl 3 C CH3OCH3 D N2O Page 3 of 6 Name GSI 9 Smelling salts are volatile chemical compounds containing nitrogen for reviving a person who is unconscious Which of the compounds listed below can you buy from a chemical company to make a smelling salt A B C D CH4N CH5N 3 CH6N CH7N 10 Why does xenon Xe have the lowest boiling point A Because there are large London forces between Xe atoms B Because it has a large mass C Because it is spherical and small 3 D Because it has the largest number of electrons 11 Dimethyl ether is soluble in water but isoflurane is not Explain why A Isoflurane molecules bond to each other with strong hydrogen bonds B The dipole moment of isoflurane is pointing away from the lone pairs 4 C Isoflurane molecules have a smaller C O C bond angle D Isoflurane molecules have a larger dipole moment 12 Three resonance structures are shown for nitrous oxide N2O Which structure is the least likely to contribute to the overall structure C A B 2 Explain your reasoning Formal charge is a model that tracks the electron distribution when atoms form molecules Formal charges different from zero indicate a the level of rearrangement of electrons Structure C has the highest formal charge 2 1 1 The negative formal charge should be on the most electronegative element oxygen not on nitrogen 4 points 13 Isoflurane is one of the most potent general anesthetics If you inhale this compound you will be unconscious almost immediately However isoflurane is not soluble in blood Low solubility in blood indicates that the molecule is not very polar This is important as it allows isoflurane to cross the blood brain barrier to act in the brain Given this information do you think a single isoflurane molecule has a large effect or a small effect Explain your thinking A Small effect 2 B Large effect 2 Explain your reasoning If a small amount of anesthetic dissolves in the blood then that same small amount will get into the brain So a few molecules must have a large effect on the body if you become unconscious after inhalation 3 points We also accepted that one molecule would not make much of a difference to something as large as the brain which is composed of so many more molecules Page 4 of 6 Name GSI Hardness of solids The Mohs …