AP Chemistry Name ________________________ Fall Semester Practice Multiple Choice Period _____ Multiple Choice: Briefly show/explain why the multiple choice answer is correct in the space provided (no calculator). 63 1. Copper has two naturally occurring isotopes, Cu and Questions 6-8 65 65 Cu. What is the abundance of Cu if the average atomic (A) Heisenberg uncertainty principle mass of copper is 63.5? (B) Pauli exclusion principle (A) 90% (B) 70% (C) 50% (D) 25% (C) Hund's rule (principle of maximum multiplicity) (D) Shielding effect 6. Can be used to predict that a gaseous carbon atom in its ground state is paramagnetic. 2. Which of the following particles is emitted by an atom of 39 39 Ca when it decays to produce an atom of K? (C) (D) 1 1 - + (A) 0n (B) 1H 7. Indicates that an atomic orbital can hold no more than two electrons. 95 3. After 195 days, a 10.0 g sample of pure Zr has decayed 95 to the extent that only 1.25 g of the original Zr remains. 95 The half-life of Zr is closest to 8. Predicts that it is impossible to determine simultaneously (A) 195 days (B) 98 days the exact position and the exact velocity of an electron. (C) 65 days (D) 49 days 9. Which set of quantum numbers (n, l, ml, ms) best describes Questions 4-5 The diagram shows the energy levels (in eV) for the valence electron of highest energy in a ground-state hydrogen gas. gallium atom (Z = 31)? (A) 4,0,0,½ (B) 4,0,1,½ (C) 4,1,1,½ (D) 4,1,2,½ Questions 10-12 refer to neutral atoms for which the atomic orbitals are represented below. (A) 1s() (B) 1s() 2s() 2p()()( ) (C) 1s() 2s() 2p()()() (D) [Ar] 4s() 3d()()()()() 10. Is in an excited state 11. Has exactly five valence electrons 12. Has the highest first ionization energy 4. What is the energy, in eV, of a photon emitted by an 13. The first seven ionization energies of element X are shown electron as it moves from the n = 6 to the n = 2 energy in the table below. -1 level in a hydrogen atom. Ionization Energy (kJ•mol ) (A) 0.38 eV (B) 3.02 eV (C) 3.40 eV (D) 13.60 eV 1st 2nd 3rd 4th 5th 6th 7th 787 1,580 3,200 4,400 16,000 20,000 24,000 On the basis of these data, element X is most likely a member of which of the following groups of elements? 5. A photon having energy of 9.4 eV strikes a hydrogen atom (A) Alkaline earth metals (B) Boron group in the ground state. Why is the photon not absorbed by (C) Carbon group (D) Nitrogen group the hydrogen atom? (A) The atom's orbital electron is moving too fast (B) The photon striking the atom is moving too fast. (C) The photon's energy is too small. (D) The photon is being repelled by electrostatic force. 14. In which of the following are the chemical species correctly 25. Which of the following molecules contains bonds that have ordered from smallest radius to largest radius? a bond order of 1.5? (A) B < C < N (B) At < Xe < Kr (A) N2 (B) O3 (C) NH3 (D) CO2 2- + (C) CI < S < S (D) Na < Na < K 26. CCl4, CO2, PCl3, PCl5, SF6 15. Of the following elements, which would be expected to Which does NOT describe any of the molecules above? have chemical properties most similar to those of sulfur, S? (A) Linear (B) Octahedral (A) Br (B) CI (C) P (D) Se (C) Square planar (D) Tetrahedral 16. Which pair of ions should have the highest lattice energy? 27. According to the VSEPR model, the progressive decrease + - + - (A) Na and Br (B) Li and F in the bond angles in the series of molecules CH4, NH3, + - + 2- (C) Cs and F (D) Li and O and H2O is best accounted for by the (A) increasing strength of the bonds (B) decreasing size of the central atom (C) increasing electronegativity of the central atom 17. Which molecule has the weakest bond? (D) increasing number of unshared pairs of electrons (A) CO (B) O2 (C) Cl2 (D) N2 28. Which of the following is a formula for an acid? 18. Which pair of atoms should form the most polar bond? (A) CH3–CO–CH3 (B) CH3–CH2–COOH (A) F and B (B) C and O (C) CH3–CH2–CH2OH (D) CH3–CH2–O–CH3 (C) F and O (D) N and F 29. Which is NOT a structural isomer of 2-methylpentane? 19. Which species has a valid non-octet Lewis structure? (A) hexane (B) 3-methylpentane (A) GeCl4 (B) SiF4 (C) NH4 + (D) SeCl4 (C) 2,2-dimethylbutane (D) 4-methylpentane 20. For which molecule are resonance structures necessary to 30. Types of hybridization exhibited by carbon atoms in a describe the bonding satisfactorily? molecule of propyne, CH3CCH, include which of the (A) H2S (B) SO2 (C) CO2 (D) OF2 following? 2 3 I. sp II. sp III. sp (A) I only (B) II only (C) III only (D) I and III only 21. The Lewis structure for SeS2 with zero formal charge has a total of (A) 2 bonding pairs and 7 nonbonding pairs of electrons. 31. Which of the following best explains why the normal boiling (B) 2 bonding pairs and 6 nonbonding pairs of electrons. point of CCI4(I) (350 K) is higher than the normal boiling (C) 3 bonding pairs and 6 nonbonding pairs of electrons. point of CF4(I) (145 K)? (D) 4 bonding pairs and 5 nonbonding pairs of electrons. (A) The C-CI bonds in CCI4 are less polar than the C-F bonds in CF4. (B) The C-CI bonds in CCI4 are weaker than the C-F bonds in CF4. (C) The mass of the CCI4 molecule is greater than that of Questions 22-24 refer to the following molecules. the CF4 molecule. (A) CO (B) CH4 (C) HF (D) PH3 (D) The electron cloud of the CCI4 molecule is more 22. Contains two -bonds polarizable than that of the CF4 molecule. 23. Has the highest dipole moment (most polar) 32. Which of the following substances exhibits significant hydrogen bonding in the liquid state? (A) CH2F2 (B) N2H4 (C) CH3OCH3 (D) C2H4 24. Has a molecular geometry that is trigonal pyramidal Questions 33-34 refer to a various points in time during an 39. At which of the following temperatures and pressures experiment conducted at 1.0 atm. Heat is added at a would a real gas be most likely to deviate from ideal constant rate to a sample of a pure substance that is solid behavior? at time to. The graph below shows the temperature of the Temperature (K) Pressure (atm) sample as a function of time. (A) 100 50 (B) 200 5 (C) 300 0.01 (D) 500 0.01 40. In which process are covalent bonds broken? (A) Solid silver melts. (B) Solid potassium chloride melts. (C) Solid carbon (graphite) sublimes. (D) Solid iodine sublimes. (A) t1 (B) t2 (C) t3 (D) t5 33. Time when the average distance between particles is greatest 41. A closed rigid container contains distilled water and N2(g) at equilibrium. Actions that would increase the concentration of N2(g) in water include which of the following? I. Shaking the container vigorously 34. Time when the temperature of the substance is between its II. Raising the temperature of the water melting point and its boiling point III. Injecting more N2(g) into the container (A) I only (B) II only (C) III only (D) I and II only 35. Heat energy is added slowly to a pure solid covalent compound at its melting point. About half of the solid melts 42. What is the mole fraction of ethanol in a 6 molal aqueous to become a liquid. Which of the following must be true solution? about this process? (A) 0.006 (B) 0.1 (C) 0.08 (D) 0.2 (A) Covalent bonds are broken as the solid melts. (B) The temperature of the solid/liquid mixture remains the same while heat is being added. (C) The volume of the compound increases as the solid melts to become a liquid. 43. What additional information is needed to determine the (D) The average kinetic energy of the molecules becomes molality of a 1.0-M glucose (C6H12O6) solution? greater as the molecules leave the solid state and (A) Volume of the solution enter the liquid state. (B) Temperature of the solution (C) Solubility of glucose in water (D) Density of the solution 36. Of the following gases, which has the greatest average molecular speed at 298 K? (A) Cl2 (B) NO (C) H2S (D) HCN 44. A solution of toluene (MM = 90 g) in benzene (MM = 80 g) is prepared. The mole fraction of toluene in the solution is 0.2. What is the molality of the solution? (A) 0.2 (B) 0.5 (C) 2 (D) 3 37. At approximately what temperature will 40. g of argon gas at 2.0 atm occupy a volume of 22.4 L? (A) 600 K (B) 550 K (C) 270 K (D) 140 K 45. Which of the following aqueous solutions has the highest boiling point at 1.0 atm? (A) 0.20 M CaCl2 (B) 0.25 M Na2SO4 (C) 0.30 M NaCl (D) 0.40 M C6H12O6 38. Three gases in the amounts shown in the table are added to a previously evacuated rigid tank. Gas Ar CH4 N2 Amount 0.35 mol 0.90 mol 0.25 mol o 46. _CH3OCH3(g) + _O2(g) _CO2(g) + _ H2O(g) If the total pressure in the tank is 3.0 atm at 25 C, the When the equation above is balanced using the lowest partial pressure of N2(g) in the tank is closest to whole-number coefficients, the coefficient for O2(g) is (A) 0.75 atm (B) 0.50 atm (A) 6 (B) 4 (C) 3 (D) 2 (C) 0.33 atm (D) 0.25 atm -1 47. What mass of KBr (MM = 119 g•mol ) is required to make 55. 2 N2H4 + N2O4 3 N2 + 4 H2O 250. mL of a 0.400 M KBr solution? What mass of N2 can be produced when 8.0 g of N2H4 (A) 0.595 g (B) 1.19 g (C) 2.50 g (D) 11.9 g (MM = 32 g) and 9.2 g of N2O4 (MM = 92 g) react? (A) 8.4 g (B) 12.6 g (C) 7.8 g (D) 10.5 g 48. Na2CO3(s) + 2 HCl(aq) 2 NaCl(aq) + CO2(g) + H2O(l) In a laboratory, a student wants to quantitatively collect the 56. A student weighs out 0.0154 mol of pure, dry NaCI in order CO2(g) generated by adding Na2CO3(s) to 2.5 M HCI(aq). to prepare a 0.154 M NaCI solution. Of the following The student sets up the apparatus to collect the CO2 gas pieces of laboratory equipment, which would be most over water. The volume of collected gas is much less than essential for preparing the solution? the expected volume because CO2 gas (A) 50 mL volumetric pipet (A) is soluble in water (B) 100 mL Erlenmeyer flask (B) is produced at a low pressure (C) 100 mL graduated beaker (C) is more dense than water vapor (D) 100 mL volumetric flask (D) has a larger molar mass than that of N2 gas, the major component of air Questions 57-60 The figures show portions of a buret used in a titration 0.0464 moles of monoprotic acid with a solution of 49. Which of the following would produce the LEAST mass of Ba(OH)2. Figures I and 2 show the level of the Ba(OH)2 CO2 if completely burned in excess oxygen gas? solution at the start and at the endpoint of the titration, (A) 10.0 g CH4 (B) 10.0 g CH3OH respectively. Phenolphthalein was used as the indicator for (C) 10.0 g C2H4 (D) 10.0 g C2H6 the titration. -1 50. A solution of RbCl (MM = 121 g•mol ) contains 11.0 % RbCl by mass. From the following list, what is needed to determine the molarity of RbCl in the solution? I. Mass of the sample Figure 1 Figure 2 II. Volume of the sample 57. What is the evidence that the endpoint of the titration has III. Temperature of the sample been reached? (A) I only (B) II only (C) III only (D) I and II only (A) The color of the solution in the buret changes from pink to colorless. (B) The color of the solution in the buret changes from blue to red. (C) The color of the contents of the flask changes from 51. CS2(l) + 3 O2(g) CO2(g) + 2 SO2(g) colorless to pink. When 0.60 mol of CS2(l) reacts as completely as possible (D) The color of the contents of the flask changes from with 1.5 mol of O2(g) according to the equation above, the blue to red total number of moles of reaction products is (A) 2.4 mol (B) 2.1 mol (C) 1.8 mol (D) 1.5 mol 58. The volume of Ba(OH), used to neutralize the acid was closest to 52. What is the empirical formula of a hydrocarbon that is 10 % (A) 22.80 mL (B) 23.02 mL hydrogen by mass? (C) 23.20 mL (D) 29.80 mL (A) CH3 (B) C2H5 (C) C3H4 (D) C4H9 59. The concentration of the Ba(OH)2 solution is closest to 53. By mixing only 0.15 M HCl and 0.25 M HCl, it is possible to (A) 1 M (B) 2 M (C) 3 M (D) 4 M create all of the following solutions EXCEPT (A) 0.21 M (B) 0.18 M (C) 0.16 M (D) 0.14 M 60. What could explain why the student calculated a concentration of Ba(OH)2 that was too large? 54. 8 H2(g) + S8(s) 8 H2S(g) (A) An extra drop of phenolphthalein was added. -1 When 25.6 g of S8(s) (MM = 256 g•mol ) reacts completely (B) A small amount of the acid was not transferred to the with an excess of H2(g) according to the equation above, titration flask. o the volume of H2S(g), measured at 0 C and 1.00 atm, (C) A drop of Ba(OH)2 remained attached to the buret tip. produced is closest to (D) Rinsing the buret with distilled water just before filling (A) 30 L (B) 20 L (C) 10 L (D) 5 L it with the Ba(OH)2 to be titrated. CaCl2(s) Ca + 2 Cl 2+ - 61. 66. The purpose of weighing the cup and its contents again at For the process of solid calcium chloride dissolving in water, the end of the experiment was to represented above, the entropy change might be expected to (A) determine the mass of solute that was added. be positive. However, S for the process is actually negative. (B) determine the mass of the thermometer. Which best helps to account for the net loss of entropy? (C) determine the mass of water that evaporated. - 2+ (A) Cl ions are much larger in size than Ca ions. (D) verify the mass of water that was cooled. (B) The particles in solid calcium chloride are more ordered than are particles in amorphous solids. 2+ - (C) Water molecules in the hydrated Ca and Cl ions are more ordered than they are in the pure water. 67. Suppose that during the experiment, a significant amount 2+ - (D) The Ca and Cl ions are more free to move around in of solution spilled from the polystyrene cup before all of the solution than they are in CaCl2(s) solute dissolved. How does this affect the calculated value for the heat of solution of the ionic compound? (A) The calculated value is too large because less water was cooled as the remaining solute dissolved. 62. For which of the processes does entropy decrease (S < 0)? (B) The calculated value is too large because some solute (A) H2O(s) H2O(l) was lost with the spilled solution. (B) Br2(l) Br2(g) (C) The calculated value is too small because less solute (C) Crystallization of I2(s) from an ethanol solution was dissolved than the student assumed. (D) Thermal expansion of a balloon filled with CO2(g) (D) The calculated value is too small because the total mass of the calorimeter contents was too small. 63. What mass of Cu(s) would be produced if 0.40 mol of Cu2O(s) was reduced completely with excess H2(g)? 68. Pb(s) Pb(l) (A) 13 g (B) 25 g (C) 38 g (D) 51 g Which of the following is true for the process represented o above at 327 C and 1 atm? (The normal melting point for o Pb(s) is 327 (C)) (A) H = 0 (B) TS = 0 (C) S < 0 (D) H = TS 64. A certain reaction is spontaneous at temperatures below 400 K but is not spontaneous at temperatures above 400 K. If H for the reaction is -20 kJ•mol and it is assumed o -1 that H and S do not change appreciably with o o temperature, then the value of S for the reaction is o 69. C(diamond) C(graphite) -1 (A) -50 J•mol •K -1 -1 (B) -20.0 J•mol •K -1 For the reaction represented above, the standard Gibbs free energy change, G 298, has a value of -2.90 kJ•mol . o -1 -1 -1 -1 -1 (C) -0.05 J•mol •K (D) -20 J•mol •K Which of the following best accounts for the observation that the reaction does NOT occur (i.e. diamond is stable) at 298 K and 1.00 atm? (A) S for the reaction is positive. o 65. ZX+Y (B) The activation energy, Ea, for the reaction is very A pure substance Z decomposes into two products, X and large. Y, as shown by the equation. Which of the following graphs o (C) The reaction is slightly exothermic (H < 0). of the concentration of Z versus time is consistent with the (D) Diamond has a density greater than that of graphite. rate of the reaction being first order with respect to Z? (A) (B) 70. When a solution is formed by adding some methanol, CH3OH, to water, processes that are endothermic include (C) (D) which of the following? I. Methanol molecules move water molecules apart as the methanol goes into solution. II. Water molecules move methanol molecules apart as the methanol goes into solution. III. Intermolecular attractions form between molecules of water and methanol as the methanol goes into solution. (A) I only (B) II only (C) III only (D) I and II only Questions 66-67 refer to an experiment to determine the heat of solution of an ionic solid. A student used a calorimeter consisting of a polystyrene cup and a thermometer. The cup was weighed, then filled halfway with water, then weighed again. The temperature of the water was Answers measured, and some of the ionic solid was added to the # Explanation cup. The mixture was gently stirred until all of the solute Average = (Mass1 x Abundance1) + (Mass2 x Abundance2) 1 D dissolved and the lowest temperature reached by the water 63.5 = (63)(1 – x) + (65)(x) = 63 – 63x + 65 x x = 0.25 (25 %) 2 D 3920Ca 3919K + 01 in the cup was recorded. The cup and its contents were It takes 3 half-lives to reduce the radioactivity to 1/8 (1.25/10.0). weighed again. 3 C 195 days/3 = 65 days From the diagram: E6 = -0.38 eV and E2 = -3.40 eV Gas solubility increases with greater partial pressure of the gas in 4 B 41 C E = E2 – E6 = -3.40 eV – (-0.38 eV) = -3.02 eV the container or lower temperature. The electron can only absorb energy that will move it to a higher 6 molal = 6 mol ethanol in 1000 g H2O 5 C energy level. 9.4 eV is not enough energy (the minimum needed 42 B 1000 g H2O x 1 mol/18 g = 55 mol H2O is -3.40 eV – (-13.60 eV) = 10.2 eV). mole fraction = 6/(6 + 55) = 0.1 The orbital diagram for C,1s() 2s() 2p()()( ), has two Molality is moles solute/kg solvent. Molarity is moles solute/L 6 C unpaired electrons (Hund's rule) = paramagnetic. 43 D solution. To determine kg solvent from L solution, you need to Pauli states that no orbital can contain electrons with the same know density; then subtract g solute. 7 B 0.2 mole fraction = 0.2 mol toluene in 0.8 benzene spin. Since two spins, this limits the number to two electrons. Heisenberg states that the wave nature of matter (DeBroglie) 44 D 0.8 mole x 80 g/1 mol = 60 g benzene 8 A molality = 0.2 mol/0.060 kg = 3 m limits what we can know about position and velocity. Electron # 31 is located in the 4th row (n = 4), 13th column (p 45 B The highest boiling point = highest concentration of ions. 9 C section, l= 1), which limits ml = 1, 0 or -1 and ms = +½ or -½ (A) .2 x 3 = .6, (B) .25 x 3 = .75, (C) .3 x 2 = .6, (D) .4 x 1 = .4 (4, 1, 1, ½) fits requirement 46 C 1 CH3OCH3(g) + 3 O2(g) 2 CO2(g) + 3 H2O(g) 1s() 2s() 2p()( ): The 2p electron is in an excited 47 D 0.250 L x 0.400 mol/L = 0.1 mol KBr x 119 g/mol = 11.9 g 10 B state, otherwise it would go into the 2s sublevel. If CO2 is soluble in water, then some gas would remain in the 48 A 1s() 2s() 2p()()(): The 2 2s electrons and 3 2p water and not bubble into the gas collecting bottle. 11 C CH3OH has the lowest proportion of C (12/32) given equal electrons are in the valence shell (highest energy level) five. 49 B 1s(): The first ionized electron is from the 1s sublevel. It takes masses; CH3OH would generate the least amount of CO2. 12 A molarity = mol solute/volume solution (L). The mass is needed to the most energy to remove electrons that are close to nucleus. The biggest jump in ionization energy occurs between 4 and 5, 50 D determine the number of moles of solute. The volume is needed 13 C to determine the volume of solution. which means 4 valence electrons Carbon group. Atomic radius increases going left and down in periodic table. 0.6 mol CS2 x 3 mol Products/1 mol CS2 = 1.8 mol Products 14 C 51 D 1.5 mol O2 x 3 mol Products/3 mol O2 = 1.5 mol Products Anion is larger than atom and cation is smaller than atom. Elements in the same column in the periodic table have similar 1.5 mol Products is the lesser number. 15 D Assume 100 g of compound chemical properties. Lattice energy is a measure of ionic bond strength, which is 52 C 10 g H x 1 mol/1 g = 10 mol/7.5 = 1.33 x 3 = 4 16 D 90 g C x 1 mol/12 g = 7.5 mol/7.5 = 1 x 3 = 3 proportional to charge and inversely proportional to size. The resulting solution must have a concentration between the two 17 C Single bonds are the weakest (CO, O=O, Cl–Cl, NN) Cl2. 53 D solutions added together. 0.14 M is less then both. Most polar bond forms between atoms with the greatest 18 A 25.6 g S8 x 256 g/mol x 8 mol H2S/1 mol S8 = 0.8 mol electronegativity difference (greatest gap on the periodic table). 54 B 0.8 mol x 22.4 L/mol = 20 L SeCl4 has 34 valence electrons, which require an expanded octet 19 D 0.25 mol N2H4 x 3 mol N2 x 28 g N2 = 10.5 g system (sp3d) to accommodate all the electrons. 55 A 2 mol N2H4 1 mol N2 Only SO2 has a single and double bond, which can exchange 0.1 mol N2O4 x 3 mol N2/1 mol N2O4 x 28 g N2 = 8.4 g 20 B places, thus forming resonance forms. (H2S and OF2: 2 single 0.0154 mol NaCl x 1 L/0.154 mol = 0.1 L (100 mL) bonds, CO2: 2 double bonds) 56 D The most accurate way to measure 0.1 L of solution is to use a ::S=Se:=S:: has zero formal charge. There are 4 bonds and 5 21 D volumetric flask. pairs of nonbonding electrons. 57 C Phenolphthalein changes from clear (acid) to pink (base) CO: The triple bond between C and O is composed of one 22 A Final volume – Initial volume = Change in volume sigma bond and two pi bonds. 58 C 35.75 mL – 12.55 mL = 23.20 mL H-F: The electronegativity difference is greatest between H and F 23 C 0.0464 mol H+ x 1 mol OH- x 1 mol B(A).. = 0.0232 mol B(A).. the most polar, which produces the highest dipole moment. 59 A 1 mol H+ 2 mol OH- PH3: The three H are pushed away from the pair of non-bonding 0.0232 mol B(A)../0.0232 L = 1 M 24 D electrons around phosphorus resulting in a pyramidal structure. MBa(OH)2 = (½ mol H+)/VBa(OH)2 A bond order of 1.5 means 1 sigma bond and 50% share of a pi 60 B too large MBa(OH)2 = too small VBa(OH)2 25 B bond, which is the case for O3 (O=O–O). Titrating less acid would result in smaller VNaOH CCl4 (tetrahedron), CO2 (linear), PCl3 (trigonal pyramid), PCl5 26 C Dissolving involves two process; (1) separation into ions, which (trigonal bipyramid), SF6 (octahedron) 61 C increases disorder (+S) and (2) ions combining with water The non-bonding electron pairs take up more space than bonding 27 D (solvation), which decreases disorder (-S). pairs H2O (2 pairs) < NH3 (1 pair) < CH4 (0 pair). Disorder decreases when I2(aq) I2(s). Disorder increases Acids contain the COOH functional group (B) (a is a ketone, c 28 B 62 C when s l g (A) and (B). Disorder also increases when gas is an alcohol, and d is an ether) molecules spread out (D). 4-methylpentane is the same as 2-methylpentane because you 29 D Cu2O + H2 2 Cu + H2O (balancing wasn't necessary because number from the closest end 4 becomes 2. 63 D mole Cu in reactants and products are equal) 30 D C1H3–C2C3H: C1 is sp3, C2 is sp, C3 is sp 0.80 mol Cu x 63.5 g/mol = 51 g Both molecules are non-polar, but the larger molar mass of CCl4 Tthreshold = H/S 31 D means that there are more electrons, which are more polarizable 64 A S = H/Tthreshold = -20 kJ•mol-1/400 = -0.05 kJ•mol-1•K-1 generating a stronger dispersion force. -0.05 kJ•mol-1•K-1 x 1000 J/1 kJ = -50 J•mol-1•K-1 Hydrogen bonding occurs when H is bonded to N, O or F. Only 32 B For a first order reaction, the straight line graph is ln[Z] vs. t. N2H4 has that arrangement. (CH2F2: H is not bonding to the F) 65 D (zero order is [Z] vs. t and second order is 1/[Z] vs. t) 33 D Farthest from each other in the gaseous phase, which is at t 5. At the end of the experiment, the cup contained solute and water. Melting occurs along 1st plateau (t2) and boiling along 2nd plateau 66 A If this value is subtracted from the mass of the cup and water, 34 C (t4) the time between these two temperatures is t3. then the difference is the mass of the solute. (a) Covalent bonds aren't broken if its molecular. The heat needed to dissolve the remaining solute had to come 35 B (c) Volume only increases if liquid state is less dense. 67 A from less water, which would make T greater than it should have (d) Temperature doesn't increase KE is not greater. been (H = -mcT) H would be too large. 36 D At the same temperature, lighter molecules have greater speed. 68 D At the normal melting point: G = 0 = H – TS H = TS 40 g of Ar = 1 mol. One mole at STP = 22.4 L. Since P is 2 x 37 B The reaction is spontaneous, but it must not occur at a fast rate. standard, then T has to be 2 x standard (V = nRT/P) 2 x 273 K 69 B This could be because the activation energy is so high, that it 38 B PN2 = XN2Ptot = (0.25/(0.35 + 0.90 + 0.25))(3.0 atm) = 0.50 atm takes too much energy to start the process. Real gases deviated from ideal behavior at low temperatures Breaking solute-solute bonds in methanol and water is 39 A (near their boiling point) and high pressure. 70 D endothermic, but forming solute-solute bonds between methanol (A) metallic bond, (B) ionic bond, (C) covalent bond, and (D) and water is exothermic. 40 C molecular bond.
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