Dr. Arrington Exam 2a (100 points), Chang Ch. 4-5 Friday, October 17, 2008

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1 Chemistry 123 Honor Pledge: Dr. Arrington Exam 2a (100 points), Chang Ch. 4-5 Friday, October 17, 2008 Show all work on problems in Section II to receive full or partial credit. Give all answers with correct units. Your exam should contain 5 pages of questions. Section I Multiple Choice (3 points each) 1. Which of the following is NOT an acid/conjugate base pair? (A) HF / F (B) H 2 SO 3 / SO 3 2 (C) NH 3 / NH 2 (D) H 2 CO 3 / HCO 3 2. The net ionic reaction of ammonia with a strong acid is (A) NH3(aq) + OH - (aq) sd H2O + NH4 + (aq) (C) OH - (aq) + H + (aq) sd H2O (E) NH3(aq) + H + (aq) sd NH4 + (aq) (B) NH4 + (aq) + HCl(aq) sd NH4Cl(aq) + H + (aq) (D) NH3(aq) + H2O sd NH4 + (aq) + OH - (aq) 3. In our study of reaction types, we had three categories of reaction: precipitation (PPT), acid-base (AB), and redox (RD). Categorize the reactions listed below are what type respectively I.) II.) III.) 3NaOH(aq) + H 3 PO 4 (aq) sd 3H 2 O(l) + Na 3 PO 4 (aq) 3H 2 SO 4 (aq) +2NaI(aq) sd I 2 (aq) + 2H 2 O(l) + SO 2 (g) +Na 2 SO 4 (aq) HCl(aq) + AgNO 3 (aq) sd AgCl(s) + HNO 3 (aq) (A) PPT, AB, RD (B) PPT, RD, PPT (C) AB, RD, PPT (D) AB, AB, RD (E) AB, AB, AB 4. The weak acid(s) found in question # 2 above is (are) (A) H 2 SO 4 only (B) H 3 PO 4 only (C) HNO 3 only (D) H 2 SO 4 and H 3 PO 4 (E) H 3 PO 4 and HNO 3 (F) all acids are strong acids 5. Illustrated at the right is a gas reservoir connected to the left arm of a mercury manometer. The right arm of the manometer is open to the atmosphere. If the difference in the heights of the mercury columns is 12.8 cm, and the barometric pressure is Torr, what is the pressure of the gas? (A) atm (B) 2.13 atm (C) atm (D) 1.00 atm (E) 1.15 atm (F) atm 6. As we picture molecules in the gas phase, which aspect below is not part of our model of ideal gases? (A) The mass of a gas sample is negligibly small. (B) The volume of a molecule is a negligibly small fraction of the volume of the container. (C) The number of molecules in a gas sample is very large. (D) The molecules are in a state of constant, random motion. (E) The attractive forces between molecules are negligibly small.

2 7. Which statement(s) is(are) correct? 1. Al(s) can reduce Fe 2+ (aq) 2. Zn 2+ (aq) can reduce Na(s) 3. Zn 2+ (aq) can oxidize Co(s) (A) 1 only (B) 2 only (C) 3 only (D) 1 and 2 only (E) 2 and 3 only (F) all are true 8. Shown at the right are the molecular speed distribution functions for a gas at two different temperatures (T1 and T2). True or False: 1.) More molecules at T1 have speeds faster than 1000 m/s T2. 2.) The average kinetic energy of the molecules is the higher at temperature T1 compared to T2. (A) True, True (C) False, False (B) False, True (D) True, False 9. In order to precipitate iron ions from solution one could add: I) KOH(s) II) CaCO 3 (s) III) Na 3 PO 4 (s) (A) I only (B) II only (C) III only (D) II and III (E) I and III (F) I, II, III 10. Which solution will be the best conductor of electricity? (A) 0.25 M CH 3 COOH (C) 0.30 M potassium chloride (B) 0.25 M magnesium bromide (D) 0.30 M acetone, C 2 H 6 O 11. The concentration of hydrogen peroxide (H 2 O 2 ) in an H 2 O 2 solution can be determined if the solution is acidified and titrated with potassium permanganate, according to the chemical reaction below. What is the molarity of a H 2 O 2 solution if ml of the solution requires ml of M KMnO 4 for complete titration? 2 MnO 4 - (aq) + 5 H2 O 2 (aq) + 6 H + (aq) sd 5 O 2 (g) + 2 Mn 2+ (aq) + 8 H 2 O(l) (A) M (B) M (C) 3.52 M (D) M (E) M (F)1.76 M 12. In question 11 above, which species is the oxidizing agent? (A) MnO 4 - (B) H 2 O 2 (C) H + (D) O 2 (E) Mn 2+ (F) H 2 O

3 13. Which plot below best represents real gas behavior, and at 100 atm which condition is correct for the gas shown below. (A) I and P Ideal > P Real (B) II and P Ideal > P Real (C) I and P Real > P Ideal (D) II and P Real > P Ideal 14. In which of the following half-reactions is a reduction occurring? (A) SO 3 SO 4 2 (B) SO 2 HSO 3 (C) OH H 2 O 2 (D) Mn 2 O 3 Mn 2+ (E) CrO 4 2 Cr 2 O An ideal gas at 299 K and 770 mm Hg is contained in a moveable piston. What must the temperature be to double the volume at constant pressure? (A) 150 o C (B) 75 o C (C) 27 o C (D) 325 o C (E) 600 o C (F) Insufficient data to determine. 16. In order to prepare 5.00 L of 0.15 M HCl solution you would require how many ml of 12 M HCl? (A) ml (B) 0.40 ml (C) 63 ml (D) 4.0 x 10 2 ml (E) 4.0 x 10 5 ml (F) 180 ml 17 The 2008 Nobel Prize in Chemistry was awarded for (A) Developing uses of green fluorescent protein. (B) Identifying the pathway of electron transport in virus signaling. (C) Isolating nanoparticles used in today s super computers. Section II (Show all work to receive full and partial credit.) 18. (6 points) The female dancers in the pictures to the right are both a little clumsy. Explain, with at least one mathematical equation, why the misstep caused significantly more pain to the male dancer in the leftmost couple than to the male dancer in the rightmost couple.

4 19. (9 points) Calculate the concentration of sodium ions in a solution that is prepared by mixing 65 ml of 0.88 M sodium phosphate with 50 ml of 1.2 M sodium nitrate. [Na + ] = M 20. (10 points) A liquid of mass g is introduced into a syringe like the one pictured to the right by injection through the rubber tip using a hypodermic needle. The syringe is then transferred to a temperature bath heated to 45 o C, and the liquid vaporizes. The final volume of the vapor (measured by the outward movement of the plunger) is 6.22 ml and the atmospheric pressure is 760 mm Hg. Given that the compound s empirical formula is CH 2, determine the molecular formula of this hydrocarbon.

5 21. (25 points) A ml solution containing unknown amounts of HCl and HNO 3 is titrated with M NaOH. It is found that ml of NaOH is required to reach the end point. (a) What are the total moles of acid in the original sample? moles H + (b) After the titration is completed excess AgNO 3 (aq) is added to the titrated acid solution. A white precipitate is collected, dried and found to have a mass of mg. Write the net ionic equation for the precipitation reaction that occurs with the addition of AgNO 3 (aq). (c) From the precipitation reaction determine the concentrations of HCl and HNO 3 in the original ml sample of acid. M HCl M HNO 3

6 -Useful Conversions & Scratch Paper- R = L atm K mol g = 1 amu 1 inch = 2.54 cm 1atm = 760 mmhg = 760 Torr 1 cm 3 = 1 ml Reducing potential table

Page 1. Exam 2 Review Summer A 2002 MULTIPLE CHOICE. 1. Consider the following reaction: CaCO (s) + HCl(aq) CaCl (aq) + CO (g) + H O(l)

Page 1. Exam 2 Review Summer A 2002 MULTIPLE CHOICE. 1. Consider the following reaction: CaCO (s) + HCl(aq) CaCl (aq) + CO (g) + H O(l) Page 1 MULTIPLE CHOICE 1. Consider the following reaction: CaCO (s) + HCl(aq) CaCl (aq) + CO (g) + H O(l) The coefficient of HCl(aq) in the balanced reaction is. a) 1 b) 2 c) 3 d) 4 e) 0 2. Given the information