Chem 112 Exam 1 Version A Spring /16/ :00am/Odago, M. O.

Size: px

Start display at page:

Download "Chem 112 Exam 1 Version A Spring /16/ :00am/Odago, M. O."

Claude Norman
5 years ago
Views:

1 Chem 112 Exam 1 Version A Spring /16/ :00am/Odago, M. O. 1. The pressure of a certain gas is measured to be 25.1 mmhg. What is this pressure expressed in units of pascals? (1 atm= x10 5 Pa and 760mmHg = 1 atm) a) Pa d) Pa b) Pa e) Pa c) Pa 2. Which of the following is a correct statement of Charles s law, V k T =? a) The pressure of a gas sample varies inversely with the volume. b) The volume of a gas sample varies directly with the absolute temperature. c) The volume of a gas varies proportionally with the pressure. d) All gas samples of the same volume at STP contain the same number of molecules. e) All gas samples of the same volume at STP contain the same number of atoms.. A 27.0 L sample of nitrogen at 7.85 atm and 27 C is simultaneously expanded to 6.4 L and heated to 5 C. What is the new pressure of the gas? a) 4. atm d) 212 atm b) 168 atm e).26 atm c).4 atm 4. What is the pressure of a 2.2 L gas sample containing 4.76 mol of gas at 42.0 C? (R = L atm/(k mol), 1 atm = 760 mmhg) a) 5.1 mmhg d) mmhg b) mmhg e) mmhg c) mmhg 5. How many moles of gas are in a gas sample occupying 1.77 L at 62 mmhg and 298 K? a).70 mol d) 16.9 mol b) mol e) 45.1 mol c) mol 6. Calculate the root mean square velocity for the O 2 molecules in a sample of O 2 gas at 22.5 C. (R = J/Kmol) a) 12.4 m/s d) m/s b) m/s e) m/s c) m/s 7. What is the name for the following phase change that happens when I 2 (l) I 2 (s)? a) melting b) sublimation c) freezing d) condensation e) vaporization 1

2 8. Molecular speed distributions for a gas at two different temperatures are shown below. Which of the following graphs correctly describes the distributions at the two temperatures, where T 2 > T 1? NOTE: The small vertical lines indicate average speed. a) c) b) d) e) none of the above 9. A liquid has an enthalpy of vaporization of 0.8 kj/mol. At 27 K it has a vapor pressure of 102 mmhg. What is the normal boiling point of this liquid? (R = 8.1 J/(K mol)) a) 27 K d) 28 K b) 20 K e) 257 K c) 292 K 10. For a particular liquid, raising its temperature from 298 K to 18 K causes its vapor pressure to double. What is the enthalpy of vaporization of this liquid? (R = 8.1 J/(K mol)) a) 115 kj/mol c) 27. kj/mol b) 288 kj/mol d) 2.5 kj/mol e) 270 kj/mol 11. What is the enthalpy of vaporization of a compound that has a vapor pressure of 157 mmhg at 25 K and 0.58 mmhg at 191 K? (R = 8.1 J/(K mol)) a).1 kj/mol d) 9.4 kj/mol b) 0.88 kj/mol e) 89 kj/mol c) 815 kj/mol 12. Which of the following pure substances has the lowest vapor pressure at 25 C? a) H 2 O d) AsH b) NH e) SbH c) PH 2

3 1. Below is a phase diagram for a substance. What is the name for point Z on the diagram? a) normal boiling point. b) boiling point. c) melting point. d) critical point. e) triple point. 14. Why does hydrogen fluoride has an unusually high normal boiling point compared to the other hydrogen halides? a) The H F bond in hydrogen fluoride is very strong. b) Hydrogen fluoride is capable of forming hydrogen bonds. c) Hydrogen fluoride has very strong London dispersion forces. d) Hydrogen fluoride is ionic. e) Hydrogen fluoride is covalent. 15. When a water molecule forms a hydrogen bond with another water molecule, which atoms are involved in the interaction? a) A hydrogen from one molecule and a hydrogen from the other molecule. b) A hydrogen from one molecule and an oxygen from the other molecule. c) An oxygen from one molecule and an oxygen from the other molecule. d) Two hydrogens from one molecule and one oxygen from the other molecule. e) Two hydrogens from one molecule and one hydrogen from the other molecule. 16. Which of the following is an ionic solid? a) Na(s) b) CsF(s) c) CO2(s) d) SiO 2 (s) e) Ne(s) 17. Which one of the following statements about solid Cu (face centered cubic unit cell) is incorrect? a) It will conduct electricity. b) There are two atoms per unit cell. c) The number of atoms surrounding each Cu atom is 12. d) The solid has a cubic closest packed structure. e) The length of a face diagonal is four times the Cu radius. 20. The metal palladium crystallizes in a face centered cubic lattice with an edge length of 88.8 pm. What is the density of palladium? a) 6.01 g/cm b) g/cm c).01 g/cm d) 1.50 g/cm e) 12.0 g/cm

4 21. The metal chromium crystallizes in a body centered cubic lattice. If the density of chromium is 7.14 g/cm, what is the unit cell edge length? a) 20 pm d) 77.5 pm b) 289 pm e) 61.1 pm c) 77.0 pm 22. The metal cesium crystallizes in a body centered cubic lattice. If the density of cesium is 1.88 g/cm, what is the unit cell volume? a) pm d) pm b) pm e) pm c) pm 2. The volume of a sample of gas measured at 25.0 C and 1.00 atm pressure is 10.0 L. What must the final temperature be in order for the gas to have a final volume of 7.5 L at 1.00 atm pressure? a. 55 C b. 50. C c. 45 C d. 5 C e. 19 C 24. An empty 2.0 L soda bottle is tightly capped at 22 C and 650 mmhg. If the bottle is placed in water at 95 C, what is the pressure in the bottle? a. 520 mmhg d. 90 mmhg b. 780 mmhg e mmhg c. 810 mmhg 25. Calcium nitrate will react with ammonium chloride at slightly elevated temperatures, as represented in the equation Ca(NO ) 2 (s) + 2NH 4 Cl(s) 2N 2 O(g) + CaCl 2 (s) + 4H 2 O(g) A.00 mol sample of each reactant will give what volume of N 2 O at STP? a L d L b L e L c..6 L 26. The density of a gas is.48 g/l at STP. What is its molecular weight? a g/mol d. 2.0 g/mol b. 224 g/mol e. 147 g/mol c g/mol 27. Which of the following has the lowest boiling point? a. H 2 O b. HF c. HCl d. HBr e. HI 4

5 28. The valence electrons in a metal crystal are a. delocalized between every two atoms. b. localized between every two atoms. c. free to travel throughout the crystal. d. found only on the surface of the crystal. e. delocalized by an applied potential. 29. Tantalum crystallizes in a body centered cubic system. If the edge of the unit cell is 479 pm and the atoms touch along the body diagonal, what is the radius of a tantalum atom in picometers? a) 240 pm d) 59 pm b) 207 pm e) 1110 pm c) 169 pm 0. Cerium crystallizes in the face centered cubic system. If the edge of the unit cell is 757 pm, what is the radius of a cerium atom in picometers? a) 268 pm d) 79 pm b) 2140 pm e) 1510 pm c) 28 pm 5

6 The information given below may be useful. Many other relations may also be derived. Equations Ideal gas equation; PV = nrt, also expressed in terms of density as PM = drt nrt Real gas equation; P = ( V - nb 2 na ) 2 V Root mean square velocity of a gas; u = RT M (also known as Van der Waals equation) 1/2 Clausius Clapeyron equation; ln 2 Volume of a sphere = 4 r P P = ΔHvap R T1 T2 π, Volume of a cube = l The edge length of the cubic unit cells l= 2r (for a simple cubic cell) l = 4r (for a body centered cubic cell) l =2 2r or simply l= ( 8) r (for a face centered cubic cell) Metric and other unit conversions 1 m = 1.0x10 2 cm 1 Kg = 1.0 x10 g 1 m =1.0x10 9 nm 1 KJ = 1.0 x10 J 1 m =1.0x10 12 pm 1 atm=760 mmhg 1 atm=1.0125x10 5 Pa Constants R = L. atm/(k. mol) Molar Gas Volume = 22.4L R= J/(K.mol) 6

Chem. 112 spring 2012 Exam 1 7:30am/Odago Wednesday March 7, 2012

Chem. 112 spring 2012 Exam 1 7:0am/Odago Wednesday March 7, 2012 Attempt all the questions and fill in your answers correctly on the scantron provided 1. A particular gas exerts a pressure of 4.6 atm.