Chemistry Exam Review PDF

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Review materials and practice questions for general chemistry...

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CHEMISTRY 1311: General Chemistry I University of Houston-Clear Lake Final Exam Study Guide Exam Coverage • Open Stax Atoms First 2nd Edition, Chapters 1-10 (sections covered in class; see last slide in PowerPoint videos for pages/sections/topics to exclude) • About 10-15% of the points will come from Chapter 10, since that material has not yet been tested • You will need to commit the following material to memory (or be able to figure it out during the exam): ⇒ Figure 3.40 (charges on ions in groups 1-2 and 15-18) ⇒ Figure 3.26 (filling order for atomic orbitals) ⇒ Figure 4.19 (you will get a table with electron-pair geometries but will need to know the names of molecular shapes when there are unshared electron pairs on the central atom) ⇒ Definitions of various concentration units (molarity, mass %, volume %, ppm, and ppb) Resources Provided • Chem 1311 Final Exam Resource Sheet (identical to the Exam 3 sheet)  Hard copy will be provided to those taking the exam on campus  Electronic version may be opened in the Respondus Lockdown Browser when you access the exam • Other needed information (such as conversion factors) will be provided in the problem or as an attachment to the exam. • Chem 1311 Exam  Hard copy will be provided to those taking the exam on campus  Electronic version will be made available in Blackboard to those taking the exam online, provided that Respondus Lockdown Browser has been installed on the device used to take the exam What You Need to Bring or Have Available During Exam • A non-programmable calculator; cell phone calculators are not permitted and there will be no sharing • Extra batteries for your calculator (if your batteries die you will have to do calculations manually) • On campus test takers: Pencils or pens for writing (an eraser is recommended but not required) • Online test takers:  Wifi device where you can access the Internet and log into Blackboard in order to take the exam. Device must support Respondus Lockdown Browser and have it installed prior to the exam  Second Wifi device with Zoom installed and camera/microphone on (fully charged or on a charger is recommended); the camera must transmit a continuous image of you and your workspace while you are taking the exam.  An exam submitted by anyone not present in Zoom classroom with camera on will receive a zero for the exam, as we have no way of verifying that you did the exam without assistance  Must provide cell phone # or other # where you can be reached during the exam; if we do not have a # on file from previous exams, we will pull you into a breakout room to obtain it. Exam Format (300 points total) • Multiple choice, 225 points (Choose 25 of 28 questions, 9 points each, one attempt per question) • Short answer, 75 points (Choose 5 of 6 questions @ 15 points each) • NOTE: work must be shown for full credit on the short-answer calculation questions.

Chemistry 1311

Final Exam Study Guide

Learning Outcomes and Sample Questions For chapters 1-9, consult the previous study guides Chapter 10: Liquids and Solids Lecture 10A. Intermolecular Forces Learning Outcome 1: Identify the intermolecular forces in a given compound or molecule The molecules in a sample of solid SO2 are attracted to each other by a combination of a. dispersion forces and H-bonding b. dispersion forces and dipole-dipole interactions c. H-bonding and ionic bonding d. covalent bonding and dipole-dipole interactions e. none of these

Learning Outcome 2: Rank a series of substances in order of increasing or decreasing intermolecular forces. Which of the molecules below will have the weakest intermolecular forces? a. H2O

b. HCl

c. H2

d. O2

e. Cl2

Lecture 10B. Intermolecular Forces and Physical Properties Learning Outcome 1: Describe the role of intermolecular forces (IMFs) on boiling point, viscosity, and surface tension In which of the following groups of substances would dispersion forces be the only significant factors in determining boiling points? I. Cl2 II. HF III. Ne IV. KNO2 V. CCl4 a. I, III, V

b. I, II, III

c. II, IV

d. II, V

e. III, IV, V

Learning Outcome 2: Rank a series of substances in order of one of their physical properties. Which of the following is the correct order of boiling points for KNO3, CH3OH, C2H6, Ne? a. Ne < CH3OH < C2H6 < KNO3 b. KNO3 < CH3OH < C2H6 < Ne c. Ne < C2H6 < KNO3 < CH3OH d. Ne < C2H6 < CH3OH < KNO3 e. C2H6 < Ne < CH3OH < KNO3

Lecture 10C. Phase Transitions Learning Outcome 1: Calculate the enthalpy change for each process on typical heating or cooling curves

Chemistry 1311

Final Exam Study Guide

How much energy is needed to convert 54.1 grams of ice at 0.00°C to water at 75.0°C? specific heat (ice) = 2.10 J/g°C specific heat (water) = 4.18 J/g°C heat of fusion = 333 J/g heat of vaporization = 2258 J/g a. 1.94 kJ

b. 17.0 kJ

c. 26.5 kJ

d. 35.0 kJ

e. 139 kJ

Assume 12,500 J of energy is added to 2.0 moles (36 grams) of H2O as an ice sample at 0°C. The molar heat of fusion is 6.02 kJ/mol. The specific heat of liquid water is 4.18 J/g °C. The molar heat of vaporization is 40.6 kJ/mol. The resulting sample contains which of the following? a. only ice b. ice and water c. only water d. water and water vapor e. only water vapor Learning Outcome 2: Correlate enthalpies of phase changes with intermolecular attractive forces Which substance is predicted to have the largest ∆Hvap and why? CH CH

2

CH

3

O CH

2

H 3C

HO

propanol

2

CH

O

methyl ethyl ether

3

C CH

H3C

3

acetone

Lecture 10D. Phase Diagrams Learning Outcome: Predict the physical state or phase changes of a substance using a phase diagram. Below is a phase diagram for compound Q. You wish to purify a sample of Q that was collected at P = 1.0 atm and T = 100 K by subliming it. In order to sublime the sample, you should:

a. b. c. d. e.

Increase P to 1.5 atm and then increase T to 300 K. Increase T to 300 K, keeping P = 1.0 atm. Lower P to 0.5 atm and then increase T to 200 K. Increase T to 300 K and then lower P to 0.5 atm. Abandon the attempt to sublime Q

Chemistry 1311

Final Exam Study Guide - ANSWERS

Answers to Sample Questions Chapter 10: Liquids and Solids Lecture 10A. Intermolecular Forces Learning Outcome 1: Identify the intermolecular forces in a given compound or molecule The molecules in a sample of solid SO2 are attracted to each other by a combination of a. dispersion forces and H-bonding SO 2 is polar because of the unshared electron pair b. dispersion forces and dipole-dipole interactions on S. All molecules have dispersion forces, and c. H-bonding and ionic bonding polar molecules also have dipole-dipole forces. d. covalent bonding and dipole-dipole interactions e. none of these

Learning Outcome 2: Rank a series of substances in order of increasing or decreasing intermolecular forces. Which of the molecules below will have the weakest intermolecular forces? a. H2O

b. HCl

c. H2

d. O2

e. Cl2

Explanation: Water has hydrogen bonding and dispersion forces, and HCl has dipole-dipole forces as well as dispersion forces. The other three molecules have only dispersion forces, which are the weakest type of IMF. The smallest molecule, H2, has the weakest dispersion forces because it has the fewest electrons and therefore the fewest opportunities to form the instantaneous dipoles that produce dispersion forces. Lecture 10B. Intermolecular Forces and Physical Properties Learning Outcome 1: Describe the role of intermolecular forces (IMFs) on boiling point, viscosity, and surface tension In which of the following groups of substances would dispersion forces be the only significant factors in determining boiling points? I. Cl2 II. HF III. Ne IV. KNO2 V. CCl4 a. I, III, V

b. I, II, III

c. II, IV

d. II, V

e. III, IV, V

Explanation: Dispersion forces are the only IMFs present in nonpolar molecules and individual atoms. Other molecules have dispersion forces, but if they also have dipole-dipole forces, hydrogen bonding, or ionic bonding, those stronger forces are more significant. Thus, we consider only the nonpolar molecules and individual atoms which are I, III, and V. Reminder: CCl4 has polar bonds but its symmetry makes it nonpolar overall. Learning Outcome 2: Rank a series of substances in order of one of their physical properties. Which of the following is the correct order of boiling points for KNO3, CH3OH, C2H6, Ne?

Chemistry 1311 a. b. c. d. e.

Final Exam Study Guide - ANSWERS

Ne < CH3OH < C2H6 < KNO3 KNO3 < CH3OH < C2H6 < Ne Ne < C2H6 < KNO3 < CH3OH Ne < C2H6 < CH3OH < KNO3 C2H6 < Ne < CH3OH < KNO3

Start by identifying the intermolecular forces in each substance. KNO3: ionic bonding (HIGHEST) CH3OH: hydrogen bonding (note the H on an O) SECOND HIGHEST C2H6: dispersion (but stronger than Ne since it's so much larger; THIRD HIGHEST Ne: dispersion (LOWEST)

Lecture 10C. Phase Transitions Learning Outcome 1: Calculate the enthalpy change for each process on typical heating or cooling curves How much energy is needed to convert 54.1 grams of ice at 0.00°C to water at 75.0°C? specific heat (ice) = 2.10 J/g°C specific heat (water) = 4.18 J/g°C heat of fusion = 333 J/g heat of vaporization = 2258 J/g a. 1.94 kJ

b. 17.0 kJ

c. 26.5 kJ

d. 35.0 kJ

e. 139 kJ

Ice at 0o → Water at 0o = Melting, so use ∆Hfus: (54.1 g)(333 J/g) = 18,015.3 J Water at 0o → Water at 75 = Temp change, so use q = c*m*∆T = (4.18 J/g°C)(54.1 g)(75-0)oC =26,960.35 J Add them up and convert to kJ: 34975.65 J(1 kJ/1000 J) = 35.0 kJ Assume 12,500 J of energy is added to 2.0 moles (36 grams) of H2O as an ice sample at 0°C. The molar heat of fusion is 6.02 kJ/mol. The specific heat of liquid water is 4.18 J/g °C. The molar heat of vaporization is 40.6 kJ/mol. The resulting sample contains which of the following? a. only ice Figure out how much heat it will take to melt the ice: b. ice and water 2.0 moles*6.02 kJ/mole = 12.04 kJ = 12,040 J c. only water Since 12,500 J of heat was added and it only takes 12,040 to melt the ice, d. water and water vapor then the ice will be completely melted and there will be 460 J left over. Is e. only water vapor this enough to vaporize the water? First we need to see how much it would take to warm the water from 0oC to 100oC (boiling point of water) q = c*m*∆T = (4.18 J/g °C)(36 g)(100) = 15,048 J Since we only have 460 J left, there's not enough to heat the water to the boiling point, so there will only be liquid water in the sample. Learning Outcome 2: Correlate enthalpies of phase changes with intermolecular attractive forces Which substance is predicted to have the largest ∆Hvap and why? CH CH

2

CH

O

3

CH

2

H 3C

HO

propanol

2

CH

O

methyl ethyl ether

3

C CH

H C 3

3

acetone

Explanation: Propanol has hydrogen bonding, while the other two compounds only have dipole-dipole forces. The high intermolecular forces mean that it requires much more energy to overcome those forces and allow the molecules to go into the gas phase.

Chemistry 1311

Final Exam Study Guide - ANSWERS

Lecture 10D. Phase Diagrams Learning Outcome: Predict the physical state or phase changes of a substance using a phase diagram. Below is a phase diagram for compound Q. You wish to purify a sample of Q that was collected at P = 1.0 atm and T = 100 K by subliming it. In order to sublime the sample, you should:

L

S G

Explanation: First, make sure you can identify the states of matter in each region on a phase diagram. Don't assume they will be labeled! Next, think about the definition of sublimation: going from solid to gas, without become a liquid first. Then evaluate each of the steps, using the graph. a. Increase P to 1.5 atm and then increase T to 300 K. INCORRECT - see red line; this would melt it b. Increase T to 300 K, keeping P = 1.0 atm. INCORRECT - see blue line; this would first melt it then vaporize it (not what we want to do) c. Lower P to 0.5 atm and then increase T to 200 K. CORRECT - this would take the sample from the solid phase directly into the gas phase d. Increase T to 300 K and then lower P to 0.5 atm. INCORRECT - as in b, you would first move into the liquid phase, which is not what you're being asked to do. e. Abandon the attempt to sublime We can rule out this answer since c would accomplish the task....