Chemistry 223 Spring 2012 Oregon State University Exam 1 April 26, 2012 Drs. Nafshun, Watson, Richardson

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1 Chemistry 223 Spring 2012 Oregon State University Exam 1 April 26, 2012 Drs. Nafshun, Watson, Richardson Instructions: You should have with you several number two pencils, an eraser, your 3" x 5" note card, a calculator, and your University ID Card. If you have notes with you, place them in a sealed backpack and place the backpack OUT OF SIGHT or place the notes directly on the table at the front of the room. Fill in the front page of the Scantron sheet with your last name, first name, middle initial, student identification number, and section number (below). Leave the test form number number blank. Section 001 (MWF 8am with Dr. Nafshun) Section 002 (MWF 9am with Dr. Nafshun) Section 003 (MWF 11am with Dr. Watson) Section 004 (MWF 1pm with Dr. Richardson) Section 005 (MWF 3pm with Dr. Nafshun) This exam consists of 22 multiple-choice questions; each has 5 points attached. The last question (Question 23) has 2 points attached. When you finish this exam, proceed to the proctor. Submit your completed Scantron form. You may take your notecard and exam packet with you.

2 K a [CH 3 COOH (aq)] = 1.80 x 10-5 (acetic acid) K a [C 6 H 5 COOH (aq)] = 6.30 x 10-5 (benzoic acid) K a [CH 2 ClCOOH (aq)] = 1.40 x 10-3 (chloroacetic acid) K b [NH 3 (aq)] = 1.80 x 10-5 (ammonia) K a [HF (aq)] = 6.30 x 10-4 (hydrofluoric acid) K a [CH 3 CH 2 CH 2 CH 2 COOH (aq)] = 1.45 x 10-5 (pentanoic acid) K a [HCOOH (aq)] = 1.80 x 10-4 (formic acid) K b [CH 3 CH 2 NH 2 ] = 5.37 x 10-4 (ethylamine) K sp [PbF 2 ] = 3.6 x 10-8 K sp [MgF 2 ] = 3.7 x 10-8 K sp [Cd(OH) 2 ] = 7.2 x K sp [PbI 2 ] = 1.4 x 10-8 K sp [CaSO 4 ] = K sp [CaC 2 O 4 ] =

3 1. Consider a M C 6 H 5 COOH (aq) solution. Which of the following is FALSE? C 6 H 5 COO - (aq) is the conjugate base [H 3 O + ] is significantly greater than [C 6 H 5 COOH] H 2 O (l) is a Bronsted-Lowry base C 6 H 5 COO - (aq) is a Bronsted-Lowry base [H 3 O + ] is similar to [C 6 H 5 COO - ] 2. Consider HClO 4 and HClO 3. Which of the following statements is FALSE? HClO 4 is a stronger acid than HClO 3. K b for the reaction ClO 4 - (aq) + H 2 O (l) HClO 4 (aq) + OH - (aq) is less than K b for ClO 3 - (aq) + H 2 O (l) HClO 3 (aq) + OH - (aq). The hydroxide ion concentration in M HClO 4 (aq) is greater than the hydroxide ion concentration in M HClO 3 (aq). The ph of M HClO 4 (aq) is less than the ph of M HClO 3 (aq).

4 3. The ph of M LiOH (aq) is: The [OH - ] of M CH 3 CH 2 CH 2 CH 2 COOH (aq), pentanoic acid, is: 2.88 x M 1.32 x 10-3 M 1.0 x M 7.58 x M 2.88 x M

5 5. The poh of M Ca(OH) 2 (aq) is: Which one of the following aqueous solutions is acidic? NH 4 Cl (aq) NaF (aq) LiI (aq) KNO 3 (aq) None of the above aqueous solutions will be acidic. 7. Which of the following is TRUE? A neutral solution contains [H 2 O] = [H 3 O + ] A neutral solution does not contain any H 3 O + or OH - An acidic solution has [H 3 O + ] > [OH - ] A basic solution does not contain H 3 O + None of the above are true.

6 8. A student titrates a ml sample of M CH 3 COOH (aq) with M NaOH (aq). Which of the following is FALSE? The point at which the moles of base delivered equals the moles of acid is known as the "equivalence point." Half of the acid has been neutralized when ml of the NaOH (aq) has been delivered. Even though CH 3 COOH is a weak acid, the reaction of CH 3 COOH (aq) with NaOH (aq) proceeds nearly 100% because of the presence of the strong base. At the equivalence point, one of the species present is a substantial amount of hydroxide ion. At the equivalence point, one of the species present is the conjugate base of a weak acid. This species is not a spectator ion and results in a ph of greater than 7 at the equivalence point. 9. How many ml of M KOH are needed to completely neutralize ml of M H 2 SO 4? ml ml ml ml ml

7 10. Which of the following solutions is a good buffer system? A solution that is 0.10 M NaCl and 0.10 M HCl A solution that is 0.10 M HCOOH and 0.10 M HCOOLi A solution that is 0.10 M NaOH and 0.10 M HNO 3 A solution that is 0.10 M HNO 3 and 0.10 M KNO 3 A solution that is 0.10 M HCN and 0.10 M NaCl 11. You wish to prepare an CH 3 COOH (aq) buffer system with a ph of What ratio of CH 3 COO - (aq)/ CH 3 COOH (aq) must you use? The ph of a buffer system which is M HCOOH (aq) and M HCOONa (aq) is:

8 13. A student titrates grams of an unknown monoprotic acid to the equivalence point with ml of M NaOH (aq). The molecular mass of the unknown acid is: g/mol g/mol g/mol g/mol g/mol 14. Skatole (below) is one of many compounds that is attractive to males of various species of orchid bees, who apparently gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study. Skatole is a: strong acid weak acid strong base weak base spectator ion

9 15. Give the expression for the solubility product constant for PbCl2. [Pb 2 ][Cl ] 2 [PbCl 2 ] 2 [Pb [PbCl 2 ] ][Cl ] 2 [Pb2+][Cl ]2 [Pb 2 ] 2 [Cl ] [PbCl 2 ] [Pb2+]2[Cl ] 16. Determine the molar solubility of CaSO 4 in a solution containing M Na 2 SO M M M M 0.10 M

10 17. The molar solubility of Ag 2 S is M in pure water. Calculate the K sp for Ag 2 S A solution containing CaCl 2 is mixed with a solution of Li 2 C 2 O 4 to form a solution that is M in calcium ion and M in oxalate ion. What will happen once these solutions are mixed? A precipitate will form since Q > K sp for calcium oxalate. Nothing will happen since both calcium chloride and lithium oxalate are soluble compounds. Nothing will happen since calcium oxalate is extremely soluble. Nothing will happen since K sp > Q for all possible precipitants. There is not enough information to determine.

11 19. What is the name of the complex [Cr(en) 2 (OH 2 )Cl]Cl 2? diethylenediaminebis(aquachloro)chromium(iii) chloride aquachlorobis(ethylenediamine)chromium(iii) chloride chloroaquabis(ethylenediamine)chromate(iii) chloride aquachlorobis(ethylenediamine)chromium(ii) dichloride aquachloridebis(ethylenediamine)chromium(iii) chloride 20. The formula of potassium hexacyanoferrate(ii) is: K[Fe(CN) 6 ] K 2 [Fe(CN) 6 ] K 3 [Fe(CN) 6 ] K 4 [Fe(CN) 6 ] K 6 [Fe(CN) 6 ] 21. What is the coordination number of the metal ion in [Fe(en) 2 (OH 2 )F]Cl 2?

12 22. Which of the following is FALSE? [Co(H 2 O) 6 ] 3+ is octahedral. [Ag(NH 3 ) 2 ] + is linear. EDTA is a hexadentate ligand. Zn 2+ is the Lewis Base in [ZnCl 2 F 4 ] 4- for it is the electron pair donor. The figure below can represent the coordination compound [Co(ox) 3 ] My least favorite thing about being in CH 223 is... My liberal arts friends think I'm really smart and they always ask me to help them with their homework. Now I glow in the dark. The permanent goggle marks. There are too many phuns. My TA won't let me play with the HF. [Any response to Question 23 will receive full credit; even no response]