Houston Community College SystemDepartmental

SAMPLE Final ExaminationChemistry 1412A

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Final Sample Exam 1412A

PART I (2 points each)

Multiple choice - Please DO NOT write or mark on this paper. Write your correct answer on scantron.

1. In which colligative property (ies) does the value decrease as more solute is added?

A. boiling point B. freezing point C. vapor pressure D. freezing point and vapor pressure

2. What is the molarity of a solution prepared by dissolving 25.2 g CaCO3 in 600. mL of a water solution?

A. 0.420 M B. 0.567 M C. 0.042 M D. 0.325 M

3. What is the freezing point of an aqueous glucose solution that has 25.0 g of glucose, C6H12O6, per 100.0 g H2O (Kf = 1.86°C /m)?

A. 0.258 B. -0.258 C. 2.58 D. -2.58

4. What is the osmotic pressure in atm produced by a 1.20 M glucose (C6H12O6) solution at 25°C?

A. 29.3 B. 4.89 C. 25.1 D. 36.0

5. The vapor pressure of pure ethanol at 60°C is 349 mm Hg. Calculate vapor pressure in mm Hg at 60°C for a solution prepared by dissolving 10.0 mol of naphthalene (nonvolatile) in 90.0 mol of ethanol? A. 600 B. 314 C. 34.9 D. 69.8

6. For first-order reactions the rate constant, k, has the units

A. M s-1 B. M-1 s-1 C. M-2 s-1 D. s-1

7. For second-order reactions the slope of a plot of 1/[A] versus time is

A. k B. k/[A]0 C. kt D. -k

8. If the reaction 2A + 3D products is first-order in A and second- order in D, then the rate law will have the form rate =

A. k[A]2[D]3 B. k[A][D] C. k[A]2[D]2 D. k[A][D]2 9. In the first-order reaction A products the initial concentration of A is 1.56 M and the concentration is 0.869 M after 48.0 min. What is the value of the rate constant, k, in min-1?

A. 3.84 x 10-2 B. 2.92 x 10-2 C. 5.68 x 10-2 D. 1.22 x 10-2

10. Consider the reaction 2HI(g) H2(g) + I2(g). What is the value of the equilibrium constant, Kc, if at equilibrium, [H2] = 6.50 x 10-7 M, [I2] = 1.06 x 10-5 M, and [HI] = 1.87 x 10-5 M?

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A. 3.68 x 10-7 B. 1.97 x 10-2 C. 1.29 x 10-16 D. 50.8

11. Given the following mechanism, determine which of the species below is a catalyst?

I) C + ClO2 ClO + CO II) CO + ClO2 CO2 + ClO III) ClO + O2 ClO2 + O IV) ClO + O ClO2

A. ClO2 B. CO2 C. O D. CO

12. For the system CaO(s) + CO2(g) CaCO3(s) the equilibrium constant expression for Keq is

A. [CO2] B. 1 / [CO2] C. [CaO] [CO2] / [CaCO3] D. [CaCO3] / [CaO] [CO2]

13. The value of Kp for the reaction 2NO2(g) N2O4(g) is 1.52 at 319 K. What is the value of Kp at this temperature for the reaction N2O4(g) 2NO2(g)?

A. -1.52 B. 1.23 C. 5.74 x 10-4 D. 0.658

14. Which of the following is true for the cell shown here? Zn(s) Zn2+(aq) Cr3+

(aq) Cr(s)

A. the electrons flow from cathode to the anode B. the electrons flow from the zinc to the chromium C. the electrons flow from the chromium to the zinc D. the zinc is reduced

15. How many electrons are transferred in the following reaction? 2ClO3- + 12H+ + 10I- 5I2 + Cl2 + 6H2O

A. 10 B. 12 C. 5 D. 30

16. A voltaic cell has an E0 value of +1.00 V. The reaction :

A. is not spontaneous B. has K =1 C. has a negative G0 D. has G0 = 0

17. Which energy conversion below takes place in a galvanic cell?

A. electrical to chemical B. chemical to electrical C. mechanical to chemical D. electrical to mechanical

18. The value of Kc for the reaction C(s) + CO2(g) 2CO(g) is 1.6. What is the equilibrium concentration of CO if the equilibrium concentration of CO2 is 0.50 M?

A. 0.31 B. 0.80 C. 0.89 D. 0.75

19. Consider the reaction below: 2SO3(g) 2SO2(g) + O2(g) , H° = +198 kJ

All of the following changes would shift the equilibrium to the left except one. Which one would not cause the equilibrium to shift to the left?

A. removing some SO3 B. decreasing the temperature C. increasing the container volume D. adding some SO2

20. Calculate the pH of a solution if its [OH] = 0.000700 M and indicate whether the solution is acidic, basic, or neutral. A. 3.15, acidic B. 17.2, basic C. 10.8, basic D. 11, basic

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21. Which one of the conjugate bases of the following Brønsted-Lowry acids are incorrect?

A. ClO- for HClO B. HS- for H2S C. H2SO4 for HSO4- D. NH3 for NH4

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22. Predict whether aqueous solutions of the following compounds are acidic, basic, or neutral. Find the incorrect answer.

A. KNO3 (neutral) B. NaC2H3O2 (basic) C. KClO (acidic) D. NaCN (basic) 23. Calculate the pH of a buffer that is 0.20 M in formic acid and 0.15 M in sodium formate (Ka = 1.8 x 10-4).

A. 2.4 x 10-4 B. 3.63 C. 0.82 D. 8.33 24. If X is the solubility of a salt in moles per liter, which one of the following Ksp expressions is incorrect?

A. Ag2S, Ksp = 4X3 B. AgCl , Ksp = X2 C. BaSO4 , Ksp = 4 X2 D. Cu(OH)2 , Ksp = 4X3

25. For each of the following processes, predict whether entropy, S, is positive or negative: (i) 2K(s) + Br2(l) 2KBr(s), (ii) 2MnO2(s) 2MnO(s) + O2(g)

A. (i) positive, (ii) positive B. (i) negative, (ii) positive D. (i) positive, (ii) negative D. (i) negative, (ii) negative

26. Using the given values of S° ( J/mol.K) , calculate the value of S° for the reaction,

C2H4(g) + H2(g) C2H6(g)

S0 = 219.4 130.58 229.5 A. -120.5 J/ K B. 120.5 J/ K C. 10.1 J/ K D. -10.1 J/ K

27. Consider a galvanic cell based on the reaction below, what is the coefficient of Fe3+ in the balanced equation in acidic solution? Fe2+ + Cr2O7

2- Fe3+ + Cr3+

A. 1 B. 2 C. 3 D. 6

28. The standard reduction potentials for the following half reactions are given as follows;

Cr3+ + 3e- Cr(s) E0 = -0.73 V Br2 + 2e- 2Br- E0 = +1.09 V

What is the E0 for a voltaic cell using these reactions? A. 1.82 V B. 0.36 V C. 4.75 V D. 1.79 V

29. Which of the following represents positron? A. 1

1 H B. 0-1 e C. 0

+1 e D. 42 He

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30. Which of the following balanced equation is labeled incorrectly?

A. Beta decay, 23992 U 239

93 Np + 0-1 e

B. Alpha Bombardment, 2411 Na + 4

2 He 2713 Al +1

0 n

C. Electron capture, 74 Be + 0

-1e 73 Li

D. All are correctly labeled

31. Which of the following pairs is incorrect ?

A. ethane - C2H6 B. hexane - C6H14 C. decane - C10H22 D. heptane - C7H14

32. Which of the following is general formula for alkene with n-carbon atoms ? A. CnHn B. CnH2n+2 C. CnH2n D. CnH2n-2

33. Classify the following molecule;

CH3 -CH2 - C= O

OCH3

A. ester B. aldehyde C. ketone D. carboxylic acid 34. What is the correct IUPAC name the following compound;

Cl CH2CH3

C=C H3C Cl

A. cis-2-chloro-3-chloro-2-pentene B. 2,3-dichloro-1-methylbutene C. trans-2,3-dichloro-2-pentene D. 1-chloro-2-methylbutene

35. Which of the following is correct condensed formula for isopropanol

A. CH3- CH2 -CH2 OH B. CH3 -CH -CH3

CH3 OH C. CH3- C -CH2OH D. CH3 - H2C = CH-OH CH3

Part II-( 5 points each) Name: _______________________

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Show work- Please write your complete work in space provided. Partial credit will be given.

1. A solution is prepared by dissolving 6.00 g of an unknown nonelectrolyte in enough water to make 1.00 L of solution. The osmotic pressure of this solution is 0.750 atm at 25.0°C. What is the molecular weight of the unknown solute (R = 0.0821 L·atm/K·mol)?

2. Initial rate data were obtained for the following reaction: A(g) + 2B(g) C(g) + D(g)

initial initial initialExperiment [A], mol/L [B], mol/L rate ,Ms -1

1 0.15 0.10 0.452 0.30 0.10 1.8

3 0.15 0.20 0.9

What are the rate law and k value for the reaction?

3. If the pH of a solution is 6.30, what are the molar concentrations of H+(aq), OH−(aq) , and pOH in the solution?

4. A 50.0-mL sample of 0.50 M acetic acid, CH3COOH, is titrated with a 0.150 M NaOH solution. Calculate the pH after 25.0 mL of the base have been added (Ka = 1.8 x 10−5).

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5. If a constant current of 5.0 amperes is passed through a cell containing Cr3+ for 1.0 hour, how many grams of Cr will plate out on to the cathode? (the atomic mass of Cr is 51.996 and 1 Faraday = 96485 coulombs)

6.The half-life of Sr-90 1s 28.1 years. How long will it take a 10.0 g sample of Sr-90 to decompose to 0.10 g?

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CHEMISTRY FINAL CHEM 1412A EXAM(answers)Part I -Multiple Choice Questions (2 points each)1. D 2. A 3. D 4. A 5. B 6. D 7. A8. D 9. D 10. B 11. A 12. B 13. D 14. B15. A 16. C 17. B 18. C 19. C 20. C 21. C22. C 23. B 24.C 25. B 26. A 27. D 28. A29. C 30. D 31. D 32. C 33. A 34. C 35. B Part II – Show work1. (0.750 atm)π = MRT and M = π /RT = _____________________________________ = 0.0307M

(0.0821 L-atm/mol-K)(298K) n massunk massunk (6.00 g)M = ________ n = MxV = ______________ MWunk = ____________ = ________________________ = 196 g/mol V MWunk MxV (0.0307M)(1.00L)OR: (g) ( R) (T) (6.00) (0.0821) ( 298) MW = ---------------- = ---------------------------- = 196 g/mol

π V (0.750) ( 1.00)2. EXP 1 & 2: Concentration of A is doubled, concentration of B is kept constant, initial rate increases by a factor of 4. That means that the reaction is second order in A. EXP 1 & 3: Concentration of A is kept constant, concentration of B is doubled, initial rate increases by a factor of 2. That means that the reaction is first order in B. Rate = k [A]2[B] EXP 1: 0.45 Ms-1 = k (0.15M)2(0.10M) k = 200 M-2s-1

3. pH = 6.30 [H+] = antilog (-6.30) = 5.01 x 10-7 MpOH = 14.00 – 6.30 = 7.70 [OH-] = antilog(-7.70) = 1.90 x 10-8MOR:[H+] = 10 –pH = 10 – 6.30 = 5.01 x 10-7 M , pOH = 14 – 6.30 = 7.70 [OH-] = 10 –pOH = 10 – 7.70 = = 1.90 x 10-8M

4. molCH3COOH = 0.50Mx0.050L = 0.025mol , molNaOH = 0.15Mx0.025L = 3.75x10-3mol

CH3COOH(aq) + NaOH(aq) NaC2H3O2(aq) + H2O(l) Initial: (0.025 mol) (3.75x10-3mol) 0 0Change: -(3.75x10-3mol) -(3.75x10-3mol) (3.75x10-3mol) (3.75x10-3mol)Final: (2.13x10-2mol) 0 (3.75x10-3mol) (3.75x10-3mol)

CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(l)

(2.13x10-2mol) M CH3COOH = ___________________ = 0.283M

(0.075L) [CH3COO-]pH= pKa + log _________________ = 3.98

(3.75x10-3mol) [CH3COOH] M CH3COO

−= ___________________ = 0.05M (0.075L)

OR: Ma = M(acid) = ( MaVa/Vtot) = (0.50)(0.05)/0.075 = 0.33 M Mb = M(base) = (MbVb/Vtot) = (0.15)(0.025)/0.075 = 0.05 M PKa = -logKa = -log (1.85x10 –5) = 4.73 For weak acid strong base ; PH = PKa + log [Mb] / [Ma - Mb] = 4.73 + log [0.05] / [ 0.33 – 0.05] = 4.73 -0.753 = 3.98

5. Charge = (5.0Amp)(3600sec) = 18,000CMoles of e- = 18,000C x (1 mol e-/96485C) = 0.18656 mol e- = 0.06219 mol Cr0.06219 mol Cr = 3.233 g CrOR : Mass ( g Cr) = ( M/n) ( It/F) = ( 52/3) (5x3600/96485) = 3.233 g Cr

6. k =( 0.693/28.1yr) = 2.47 x 10-2 yr-1

ln[0.10] = -(2.47 x 10-2 yr-1)(t) + ln[10.0] t = 186 yr.

OR: t = (3.32)(t½ ) ln ( mo / mn) , t = ( 3.32) ( 28.1) log ( 10.0/0.10) , t = 186 yr.

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Houston Community College SystemDepartmental

SAMPLE Final ExaminationChemistry 1412B

Cortisone (steroid)- reduces swelling and decreases the body's immune response

Final Sample Exam 1412B

PART I (2 points each)

Multiple choice - Please DO NOT write or mark on this paper. Write your correct answer on scantron.1. In the reaction, HSO4

- + HS- ↔ H2S + SO42- , which one of the sets below constitutes a conjugate (acid-

base) pair?

A) HSO4-, HS- B) HSO4

- , H2S C) H2S , HS- D) HS-, SO42-

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2. Which one of the species below is insoluble in water?

A) ZnSO4 B) PbCrO4 C) AgNO3 D) NaC2H3O2

3. A glucose solution is prepared by dissolving 5.10 g of glucose, C6H12O6, in 110.5 g of water. What is the molality of the glucose solution?

A) 0.283 m B) 0.000256 m C) 0.245 m D) 0.256 m

4. What is the expected freezing point of a solution that contains 25.0g of fructose, C6H12O6, in 250.0g of water? Ki = 1.86 °C m-1

A) -0.10°C B) +0.10°C C) -1.03°C D) +1.86°C

5. Which of the following reactions accompanied by an increase in entropy?

A) ZnS(s) + 3/2 O2(g) → ZnO(s) + SO2(g) B) CH4(g) + H2O(g) → CO(g) + 3H2(g) C) BaO(s) + CO2(g) → BaCO3(s) D) Na2CO3(s) + CO2(g) + H2O(g) → 2 NaHCO3(s)

6. The nuclear particle which is described by the representation, 11 X, is called:

A) alpha particle B) electron C) neutron D) proton

7. Butene, C4H8, is a hydrocarbon with one bond. How many noncyclic isomers can be drawn?

A) 1 B) 2 C) 3 D) 4

8. If the OH- ion concentration in an aqueous solution at 25.0 oC is measured as 3.4 x 10-3 M, then the pH is? A) 2.47 B) 7.22 C) 8.24 D) 11.53

9. A galvanic cell has two electrodes. Which statement below is correct?

A) Reduction takes place at the anode, which is positively charged. B) Reduction takes place at the anode, which is negatively charged. C) Reduction takes place at the cathode, which is positively charged. D) Reduction takes place at the cathode, which is negatively charged.

10. If a reaction involves a single reactant is first order with a rate constant of 4.50× 10-2 s-1, how much time is required for 75.0% of the initial quantity of reactant to be used up?

A) 16.7 seconds B) 30.8 seconds C) 23.1 seconds D) 25.3 seconds

11. For the reaction, 2XO + O2 2 XO2, some data obtained from measurements of the initial rate of reaction at varying concentrations is given below.

Run # [XO] [O2] rate, mmol L-1 s-1

1 0.010 0.010 2.5 2 0.010 0.020 5.0 3 0.030 0.020 45.0

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The rate law is therefore: A) rate = k[XO]2 [O2] B) rate = k[XO] [O2] C) rate = k[XO] [O2]2 D) rate = k[XO]2 [O2]2 12. Which one of the following is the strongest acid?

A) HClO (Ka = 3.0 x 10-8) B) HF (Ka = 6.8 x 10-4) C) HNO2 (Ka = 4.5 x 10-4) D) HCN (Ka = 4.9 x 10-10)

13. Using the standard entropy values: H2(g), So = + 130.6 J mol-1 K-1 I2(s), So = + 116.12 J mol-1 K-1 HI(g), So = + 206.5 J mol-1 K-1

Calculate the standard entropy change, ∆So, for the reaction: H2(g) + I2(g) → 2 HI(g)

A) -40.8 J B) +40.8 J C) -165.3 J D) +165.3 J

14. Consider the following reaction at equilibrium:

2NH3(g) N2(g) + 3H2(g) H = + 92.4 kJ

Adding H2(g) to the system at equilibrium will ____________________

A) decrease the concentration of NH3(g) at equilibrium B) remove all of the N2(g) C) increase the value of the equilibrium constant D) decrease the concentration of N2(g) at equilibrium

15. The equilibrium constant for the reaction, H2(g) + I2(g) ↔ 2 HI(g) is 54.9 at 699.0 K. What is the equilibrium constant for 4 HI(g) ↔ 2 H2(g) + 2 I2(g) under the same condition?

A) 109.8 B) 9.11 x 10-3 C) 3.32 x 10-4 D) -109.8

16. A 0.400 M solution of an acid, HA, has a pH = 1.301. What is the value of the ionization constant, Ka, for this acid? A) 5.00 x 10-2 B) 1.25 x 10-3 C) 5.56 x 10-3 D) 6.25 x 10-3

17. What is the balanced form of the following unbalanced redox equation that takes place in an acidic medium?

NO2-(aq) + Cr2O72-(aq) Cr3+(aq) + NO3-(aq)

A) NO2-(aq) + Cr2O72-(aq) + 8H+(aq) 2Cr3+(aq) + NO3-(aq) + 4H2O(l)B) 3NO2-(aq) + Cr2O72-(aq) 2Cr3+(aq) + 3NO3-(aq) + 4H2O(l)C) 3NO2-(aq) + Cr2O72-(aq) + 8H+(aq) 2Cr3+(aq) + 3NO3-(aq) + 4H2O(l)D) 3NO2-(aq) + Cr2O72-(aq) + 16H+(aq) 2Cr3+(aq) + 3NO3-(aq) + 8H2O(l)

18. A buffer solution is prepared by taking 0.250 moles of acetic acid ( pKa = 4.74) and 0.400 moles of sodium acetate in sufficient water to make 1.800 liters of solution . Calculate the pH.

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A) 4.95 B) 4.66 C) 4.86 D) 4.56

19. Oxidation refers to ______ electrons, reduction refers to ________ of electrons.

A) Gain; gain B) Loss; gain C) Neutralization; loss D) Gain; loss

20. 40.0 ml of 0.10 M HCl(aq) was added to 50.0 ml of 0.10 M NaOH(aq) and the mixture was stirred, then tested with a pH meter. What pH should be obtained at 25.0 oC?

A) 1.95 B) 12.05 C) 7.00 D) 12.50

21. What element undergoes alpha decay to form lead-208 ( Pb)? 82 222 131

A) Radon (Rn) B) Xenon(Xe) 86 54

84 212

C) Krypton (Kr) D) Polonium (Po) 36 84

22. The solubility of silver oxalate, Ag2C2O4, in pure water is 2.06 x 10-4 moles per liter. Calculate the value of Ksp for silver oxalate from this data.

A) 4.24 x 10-8 B) 8.49 x 10-8 C) 1.75 x 10-11 D) 3.50 x 10-11

23. Hydrocarbons containing a carbon-carbon triple bond are called _____________ .

A) alkanes B) alkenes C) alkynes D) cyclic alkanes

24. The half-life of cobalt-60 is 5.3 yr. How much of a 1.000-mg sample of cobalt-60 is left after a 10.6yr priod?

A) 0.250mg B) 0.100mg C) 0.990mg D) 0.125mg

25. Which of the following salts has a cation that can hydrolyze in water?

A) NaCl B) Ca(NO3)2 C) Ba(C2H3O2)2 D) NH4Cl

26. The unit of the rate constant for a second order reaction could be _______.

A) M-1 s-1 B) M C) M s-1 D) M2s-1

27. For the reaction: A(g) + 2B(g) 4C(g), G = 77.8 kJ. If the reaction mixture consists of 2.0 atm A, 4.0 atm B, and 2.5 atm C at 298 K, calculate the G for this reaction mixture at 298 K. (R=8.314 J/molK).

A) 78.3 kJ B) 7.89 kJ C) –7.89 kJ D) -34.2 kJ

28. A galvanic cell is composed of these two half cells, with the standard reduction potentials shown

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Zn2+(aq) + 2e- ↔ Zn(s) -0.76 volt Cd2+(aq) + 2e- ↔ Cd(s) -0.40 volt What is the standard free energy for the cell reaction of this galvanic cell?

A) -69 KJ B) +69 KJ C) -224 KJ D) +224 KJ

29. The reaction 2H2O2 2H2O + O2 has the following mechanism?

H2O2 + I– H2O + IO–

H2O + IO– H2 + O2 + I–

The intermediates in the reaction are:

A) H2O and IO– B) H2O2 and I– C) H2O2 and IO– D) IO– and I–

30. Name the following compound according to IUPAC system: CH3

CH3CHCHCH2CH3

CH2CH3

A) 2,3-dimethylhexane B) 3-ethyl-2,4-dimethylheptaneC) 3-ethyl-2-methylheptane D) None of the above

31. The system, H2 (g) + X2 (g) ↔ 2 HX(g) has a value of 24.4 for the constant, Kc. A system being tried in a 3.00 liter reactor was charged with 0.150 moles of H2, 0.150 moles of X2 and, 0.600 moles of HX. The catalyst was introduced using a remote unit, and the system was allowed to come to equilibrium. Which statement below describes the situation? A) the reaction goes to the right, Q ‹ K B) the reaction goes to the left, Q ‹ K C) the reaction goes to the right, Q › K D) the reaction goes to the left, Q › K

32. A solution is made by mixing 138.2 grams of ethanol, C2H6O, (46.069 g mol-1), 103.6 gram of water (18.015 g mol-1), and 80.11 grams of methanol, CH4O, (32.0042 g mol-1). What is the mole fraction of methanol in the mixture?

A) 0.02504 B) 0.2224 C) 0.2493 D) 0.3333

33. A Lewis base is defined as a substance that

A) acts as a proton donor B) increases [H+] when placed in H2O C) decreases [OH–] when placed in H2O D) acts as a electron pair donor

34. The standard reduction potentials for the following half reactions are given as follows;

Cr+3 +3e- Cr(s) E0 = - 0.73 V Br2(aq) + 2e- 2Br- E0 = + 1.09 V

What is the E0 for this cell?

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A) 1.82 V B) 0.36 C) 4.75 V D) 1.79 V

35. Classify the following molecule:

A) ester B) aldehyde C) ketone D) carboxylic acid

Name :__________________________Part II-( 5 points each)

Show work- Please write your complete work in space provided. Partial credit will be given. 1. Solution made by dissolving 6.73 grams of toluic acid in 110 grams of benzene ( f.p. = 5.45oC, Kf = 5.07

oC/m) gave a freezing point of 3.00 oC. What is the calculated molecular weight of toluic acid form this

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data?

2. The gas phase decomposition of HI, HI(g) → 1/2H2(g) + 1/2I2(g) , has the rate equation, -∆ [HI] / ∆t = K[HI]2 where K=30.0 L/mol. min at 443°C. How much time does it take for the concentration of HI to drop from 0.010 mol/L to 0.0050 mol/L at 443°C?

3. Ka for hypochlorous acid, HClO, is 3.0x10-8. a. Calculate the pH after addition of 15.0 ml of 0.100 M NaOH to 40.0 ml of 0.100 M HClO. b. Identify the pH at half equivalent point.

4. Assuming that the value of ∆H and ∆S do not change with temperature, and using the following data, CaO(s), ∆Hf

o = -635.5 KJ mol-1, So = +40.0 J mol-1 K-1

CaCO3(s), ∆Hfo = -1207 KJ mol-1, So = +92.9 J mol-1 K-1

CO2(g), ∆Hfo = -394 KJ mol-1, So = +213.6 J mol-1 K-1

Calculate the value for the free energy change, ∆Go for the reaction,

CaCO3(s) → CaO(s) + CO2(g) at 815 Co

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5. Aluminum metal is oxidized in aqueous base with water serving as the oxidizing agent.

Al(s) + H2O(1) → Al(OH)4- + H2(g) (basic solution)

Write a balanced equation for this reaction in basic solution.

6. Refer to the following half-reactions below;

MnO4- + 8H+ + 5e- Mn2+ + 4H2O E0 = 1.51 V

Cr2O72- + 14H+ + 6e- 2Cr3+ + 7H2O E0 = 1.33 V

Calculate the value of equilibrium constant at 25 0C for this reaction?

CHEMISTRY FINAL CHEM 1412B EXAM(answers)

PART - I1. C 2. B 3. D 4. C 5. B 6. D 7. C 8. D 9. C 10. B 11. A 12. B 13. D 14. D 15. C 16. D 17. C 18. A 19. B 20. B 21. D 22. D 23. C 24. A 25. D 26. A 27. A 28. A 29. A 30. D

31. A32. B 33. D 34. A 35. A

PART - II1. ∆Tf = kf x m = kf x (n/kg) = (kf x m)/(Mxkg); M = (kf x m)/(∆Tf x kg)

M = 136.15 g/mol17

2. t = (1/k) x ((1/[A]t ) – (1/[A]o)) t = (1/30) x ((1/0.005) – (1/0.01)) t = 3.33 min.

3. a. pH = pKa + log((1.5x10-3)/(2.5x10-3)) pH = 7.30 b. At ½ equivalent point pH = pKa pH = 7.52

4. ∆Ho = 177.5 kJ ∆So = 160.7 J ∆Go = ∆Ho - T∆So

∆Go = 177.5 kJ - 1088.15 x 160.7 x 10-3 kJ ∆Go = 2.634 kJ

5. 2Al + 6H2O + 2OH- 2Al(OH) 4 - + 3H2

6. ∆G = ∆Go + RT Ln Q E = Eo – (RT/nF)Ln Q E = Eo – (0.0592/n)Log Q at equilibrium, E= 0, and Q = Keq. Log Keq. = n Eo /0.0592 = 30 x (151 – 1.33)/0.0592 Log Keq. = 91.2; Keq. = 1.58x1091

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