CHEM 101: PRACTICE FINAL EXAM

Size: px

Start display at page:

Download "CHEM 101: PRACTICE FINAL EXAM"

Charla Osborne
6 years ago
Views:

1 CHEM 101: PRACTICE FINAL EXAM Note: Answers to this practice final will be posted in the Nucleus. See Chemistry website for Randi s exam-period tutoring hours if you require help. PART 1) MULTIPLE CHOICE 1) Dalton s Law of Partial Pressures states that the total pressure for a gas is given by: a) the van der Waals equation b) the sum of the individual vapour pressures c) the sum of the partial pressures d) the molecular velocity of all gases 2) Hess s Law can be paraphrased as: a) you can t win b) that the momentum and position of an electron can t be determined simultaneously c) entropy is the disorder of the Universe d) enthalpy is a state function and overall it is independent of the number of steps 3) The relationship between pressure and volume for gases is: a) Boyle s Law b) Charles Law c) Avogadro s Law d) Graham s Law 4) The molarity of a solution that contains 14.7 g of H 2 SO 4 (MW = g/mol) in 200 ml solution is: a) 7.4 M b) 1.5 M c) 0.75 M d) 0.77 M e) 3.0 M 5) If a 20 ml solution of an unknown acid requires 24.3 ml of M NaOH to reach neutralization, what is the concentration of the unknown acid? a) M b) M c) M d) M 6) Arsenic acid, H 3 AsO 4, is used industrially to manufacture insecticides. Arsenic acid is a polyprotic acid with Ka 1 =2.5 x 10-4, Ka 2 =5.6 x 10-8, and Ka 3 =3 x What is the concentration of HAsO 4 in a solution whose initial arsenic acid concentration was 0.35 M? a) 9.4 x 10-3 M b) 2.5 x 10-4 M c) 8.8 x 10-5 M d) 5.6 x 10-8 M 7) In the hydrolysis of water by fluoride ions, the products will include: a) H 2 O b) F- c) OH - d) none of the above 8) In which compound does iodine have an oxidation state of +3? a) HIO 3 b) I 2 c) IF 5 d) HI 9) The oxidation state of aluminum in the complex ion AlCl 4 - is: a) 4 b) -4 c) -3 d) 3 e) none of the above 10) What is the maximum amount of sodium sulfate (Na 2 SO 4 ) that can be added to 1.00 L of M Ca(NO 3 ) 2 before precipitation of calcium sulfate begins (K sp =2.4 x 10-5 )? a) 1.2 x 10-2 mol b) 3.5 x 10-3 mol c) 4.9 x 10-3 mol d) 1.2 x 10-5 mol

2 11) A voltaic cell is prepared using copper and silver, as shown: Cu (s) Cu 2+ (aq) Ag + (aq) Ag(s) Which one of the following reactions occurs at the cathode? a) Cu (s) Cu 2+ (aq) + 2eb) Cu 2+ (aq) + 2e- Cu (s) c) Ag (s) Ag + (aq) + e- d) Ag + (aq) + e- Ag (s) 12) The value of E cell for Cr (s) Cr 3+ (aq) Hg 2+ (aq) Hg (l) is 1.59 V. Calculate G for the reaction at 25 C. a) -920 kj b) -767 kj c) -460 kj d) -307 kj 13) Which of the following combinations of signs for H and S will always result in a reaction being nonspontaneous? a) H +, S b) H -, S + c) H -, S - d) H +, S + e) Cannot be determined without temperature 14) The vapour pressure of 1-butene is atm at K and its heat of vaporization is 22.9 kj/mol. What is the normal boiling point of 1-butene? a) K b) K c) K d) K 15) Data for the reaction A + B C are given below. What is the rate constant for this system? Experiment [A] (M) [B] (M) Initial Rate (M s -1 ) x x x 10-5 a) 2.8 x 10-2 M -1 s -1 b) 2.8 x 10-2 M s -1 c) 2.8 x 10-2 M 2 s -1 d) 1.7 x 10-3 M -1 s -1 e) 1.7 x 10-3 M s -1

3 16) If a catalyst is added to a reaction I) the value of k is increased II) the value of k is decreased III) the rate is increased IV) the rate is decreased V) neither rate nor the constant are changed, only the order a) I and IV b) II and IV c) II and III d) I and III e) V only 17) The correct units of the specific rate constant for a zero order reaction are: a) L/mol-sec b) sec -1 c) sec d) mol 2 /L 2 sec e) none of the above 18) If the half-life of a reactant is independent of its initial concentration, the reaction order is: a) 0 b) 0.5 c) 1 d) 2 e) 3 19) The rate law for the rearrangement of CH 3 NC to CH 3 CN at 800 K is Rate = 1300 s -1 [CH 3 NC] What is the half-life of the reaction if the initial concentration of CH 3 NC is 0.40 M? a) 1.92 x 10-3 s b) 520 s c) 1875 s d) 5.33 x 10-4 s 20) The first order reaction A products has a half-life of 150 seconds. What percent of the sample remains unreacted after 300 sec? a) 25% b) 50% c) 12.5% d) 0.0% e) 75% 21) Which of the following is NOT a Lewis base? a) OH - b) (C 2 H 5 )B c) CH 3 NH 2 d) NH 3 22) Molecular orbital theory combines atomic orbitals to form: a) bonding/anti-bonding pairs b) hybrids such as sp 3 and d 2 sp 3 c) VSEPR-based molecular shapes c) lattice structures for ions 23) Markovnikov s rule states that in an addition reaction: a) the carbocation will form on the least substituted carbon atom b) the carbocation will form on the most substituted carbon atom c) H + will add to the sp 2 carbon that is bonded to the least number of hydrogens d) Markovnikov didn t play by the rules

4 PART 2) TITRATION Answer the following titration question, which has 5 parts (20 marks) A 400 ml sample of benzoic acid, a weak acid (C 6 H 5 COOH; K a =6.3 x 10-5 ), is titrated by the strong base, NaOH. The initial concentrations of the two species are: What is the ph of the solution: [C 6 H 5 COOH] = M [NaOH] = M a) Initially? b) After 199 ml of NaOH has been added to the acid? c) After 200 ml of NaOH has been added to the acid? d) At the equivalence point? e) After ml of NaOH has been added to the acid?

5 PART 3) LONG ANSWERS 1) Answer either (i) OR (ii) of the following: (i) At 850 C, the equilibrium constant, K p, for the reaction C (s) + CO 2 (g) 2CO (g) is If the total pressure in the system at equilibrium is atm, what is the partial pressure of carbon monoxide? (ii) At a temperature of 25 C and a pressure of 1 bar, a gas has a density of 2.00 g/l. What is the molar mass of the gas?

6 2) Answer either (i) OR (ii) of the following: (i) What is the molecular weight of a gas that has a molecular velocity of m/s at 25 C? What is the effusion rate of this gas compared to oxygen? (ii) If the relative effusion rate of a gas compared to oxygen is 1.173, what is its velocity at STP?

7 3) Answer either (i) OR (ii) of the following: (i) Cinnamaldehyde (MW = g/mol) is used as a flavouring agent. What mass of cinnamaldehyde must be added to 175 g of ethanol to give a solution whose boiling point is 82.7 C? K b = 1.22 C/m; boiling point of pure ethanol = 78.5 C. (ii) What is the freezing point of a solution containing 2.87 g of benzene (MW = g/mol) dissolved in 50.0 g of p-dichlorobenzene (MW = g/mol), given that the freezing point of p-dichlorobenzene is 53.0 C and K f = 7.10 K/m?

8 4) Answer either (i) OR (ii) of the following: (i) What is the ph of a M solution of carbonic acid? (Ka 1 = 4.2 x 10-7 ; Ka 2 = 4.8 x ) (ii) The titration of a 75.0 ml sample of a di-protic acid requires 24.2 ml of M KOH. What is the concentration of the acid?

9 5) Answer either (i) OR (ii) of the following: (i) A solution is prepared containing M Ag + and 1.5 M NH 3. K f for [Ag(NH 3 ) + 2 is 1.6 x What is the concentration of Ag + in this solution? (ii) Solid AgNO 3 (aq) is slowly added to a solution containing M NaCl and M NaBr in a fractional or selective precipitation experiment. What percentage of bromide will be removed before the silver chloride starts to precipitate? AgCl: K sp = 1.8 x AgBr: K sp = 5.0 x 10-13

10 6) Answer either (i) OR (ii) of the following: (i) Consider the reaction: H 2 X (g) HX (g) + X (g) H = 18.4 kj/mol; S = 23.1 J/molK What is K eq for this reaction at 525 K? (ii) Consider the reaction: 2NO 2 (g) N 2 O 4 (g) H = kj/mol; S = -175 J/molK In a container (at 298 K), N 2 O 4 (g) and NO 2 (g) are mixed with initial partial pressures of 2.4 atm and 0.42 atm, respectively. What is the pressure of each of these gases at equilibrium?

11 7) Answer either (i) OR (ii) of the following: (i) In the second order reaction, A products, [A] = M initially and M after 18.0 minutes. What is the half-life of the reaction if the initial concentration is M? (ii) For the reaction 2N 2 O 5 (g) 4NO 2 (g) + O 2 (g), the rate law is: Rate=k[N 2 O 5 ] At 310 K, the half-life is 2.50 x 10 4 seconds and the activation energy is kj/mol. What is the half-life at 360 K?

12 PART 4) ORGANIC CHEMISTRY Give the major product(s) of the following reactions. 1. Hg(OAc) 2, H 2 O 2. NaBH 4 1. BH 3 2. H 2 O 2, NaOH, H 2 O KMnO 4, H 3 O + KMnO 4, H 3 O + HBr Ether + H 2 O H 2 SO 4 HgSO 4

13 Cl 2 KMnO 4 NaOH, H 2 O

Chapter 19 Chemical Thermodynamics

Chapter 19 Chemical Thermodynamics Chapter 19. Chemical Thermodynamics Sample Exercise 19.2 (p. 819) Elemental mercury is a silver liquid at room temperature. Its normal freezing point is -38.9 o C, and its molar enthalpy of fusion is H