1996.ap - U.S. National Chemistry Olympiad: 1996 National...

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Unformatted text preview: U.S. National Chemistry Olympiad: 1996 National Test Go to Answers 1. What is the formula for the basic anhydride of Ba(OH) 2 ? (A) Ba 2 O (B) BaO (C) BaO 2 (D) Ba 2. Which element exhibits both +1 and +3 oxidation numbers in its compounds? (A) B (B) Be (C) Sn (D) Ti 3. Which element is obtained commercially by electrolysis? (A) aluminum (B) iron (C) oxygen (D) sulfur 4. A 0.1 M solution of a certain cation will form a precipitate with 0.1 M solutions of all of these anions; OH, CO 3 2 , SO 4 2 . Which cation fits this description? (A) Ba 2+ (B) Fe 2+ (C) Mg 2+ (D) Pb 2+ 5. Each of these solutions is added to a mixture of aqueous sodium bromide and chloroform,CHCl 3 . Which one will give a positive test for aqueous bromine when the solutions are vigorously mixed? (A) NaCl solution (B) NaI solution (C) NaI 3 solution (D) chlorine water 6. Oxalic acid dihydrate, H 2 C 2 O 4 . 2 H 2 O(s) is often used as a primary standard to standardize sodium hydroxide solutions. Which of these facts are reasons to choose this substance as a primary standard? I. It is diprotic. II. It is a stable compound that can be weighed directly in air. III. It is available in a pure form. (A) III only (B) I and II only (C) II and III only (D) I, II, and III 7. When FeCl 3 is ignited in an atmosphere of pure oxygen,this reaction takes place. 4 FeCl 3 (s) + 3 O 2 (g) ---> 2 Fe 2 O 3 (s) + 6 Cl 2 (g) If 3.0 mol of FeCl 3 are ignited in the presence of 2.0 mol of O 2 gas, how much of which reagent is present in excess and therefore remains unreacted? (A) 0.33 mol FeCl 3 remain unreacted (B) 0.67 mol FeCl 3 remain unreacted (C) 0.25 mol O 2 remain unreacted (D) 0.50 mol O 2 remain unreacted 8. How many grams of SbF 3 are needed to produce a gram of Freon-12, CCl 2 F 2 , according to the reation represented by this equation? 3 CCl 4 + 2 SbF 3---> 3 CCl 2 F 2 + 2 SbCl 3 Substance Molar Mass SbF 3 179 g mol 1 CCl 2 F 2 121 g mol 1 (A) 0.667g (B) 0.986g (C) 1.50g (D) 2.22g 9. A self-contained breathing apparatus uses potassium superoxide, KO 2 , to convert the carbon dioxide and water in exhaled air into oxygen, as shown by the equation. 4 KO 2 (s) + 2 H 2 O(g) + 4 CO 2 (s) ---> 4 KHCO 3 (s) + 3 O 2 (g) How many molecules of oxygen gas will be produced from the 0.0468 g of carbon dioxide that is exhaled in a typical breath? (A) 4.8 x 10 20 (B) 6.4 x 10 20 (C) 8.5 x 10 20 (D) 1.9 x 10 21 10. Magnetite, Fe 3 O 4 , can be converted into metallic iron by heating with carbon monoxide as represented by this equation. Fe 3 O 4 (s) + 4 CO(g) ---> 3 Fe(s) + 4 CO 2 (g) How many kilograms of Fe 3 O 4 must be processed in this way to obtain 5.00 kg of iron if the process is 85% efficient?...
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This note was uploaded on 11/09/2011 for the course CHEM 111 taught by Professor Rogers during the Fall '08 term at Thomas Edison State.

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1996.ap - U.S. National Chemistry Olympiad: 1996 National...

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