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1991 - U.S National Chemistry Olympiad 1991 Local Section...

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U.S. National Chemistry Olympiad: 1991 Local Section Test Go to answers 1. What is the maximum amount of MgCl 2 that can be prepared from the reaction of 10.0g of HCl with 10.0 of Mg(OH) 2 ? 2 HCl + Mg(OH) 2 ---> MgCl 2 + 2 H 2 O (A) 9.26 g (B) 13.1 g (C) 16.3 g (D) 17.5 g 2. Phenylflouroform contains 57.54% C, 3.45% H, and 39.01% F. Its molecular formula is the same as its simplest formula. How many carbon atoms are in one molecule of Phenyflouroform ? 3. What is the most likely formula for a compound of gallium and sulfur ? 4. A mixture of 2.30 x 10 23 molecules N 2 and 4.35 x 10 23 molecules N 2 O has a total pressure of 2.00 atm. What is the partial pressure of N 2 ? 5. Which element should have the smallest first ionization energy ? (A) Ca (B) Rb (C) Al
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(D) Cl 6. An aqueous solution containing 1.00 mol H 2 SO 4 is mixed with an aqueous solution containing 1.00 mol NaOH. The mixture is then evaporated to dryness. What solid remains after evaporation ? 7. Which atom is the smallest ? 8. At room temperature and 1 atm pressure the molecules are farthest apart in 9. What is the net-ionic equation for the reaction of aqueous solutions of BaCl 2 and K 2 SO 4 ? (A) Ba 2+ (aq) + 2Cl¯(aq) + 2K + (aq) + SO 4 2 ¯(aq) ---> BaSO 4 (s) + 2K + (aq) + 2Cl¯(aq) (B) Ba 2+ (aq) + SO 4 2 ¯(aq) ---> BaSO 4 (s) (C) K + (aq) + Cl¯(aq) ---> KCl(s) (D) Ba 2+ (aq) + 2Cl¯(aq) + 2K + (aq) + SO 4 2 ¯(aq) ---> BaSO 4 (s) + 2KCl(s) 10. When 80.00 mL of 0.200 M HNO 3 is added to 120.00 mL of 0.150 M KOH, the reaction HNO 3 (aq) + KOH(aq) ---> KNO 3 (aq) + H 2 O(l) occurs and the resulting solution is 11. Methanol burns in oxygen according to the equation
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CH 3 OH + O 2 ---> CO 2 + H 2 O (unbalanced) What volume of oxygen is required to burn 5.0 L of gaseous methonal measured at the same temperature and pressure ? 12. A 50 g sample of an ideal gas occupies a volume of 3.2 L at 40 °C and exerts a pressure of 2.6 atm. What is its molar mass ? 13. When sodium metal reacts with an excess of water the products are (A) Na 2 O(s) and H 2 (g) (B) Na + (aq), OH¯(aq) and H 2 (g) (C) NaH(s) and O 2 (g) (D) Na 2 O 2 (s) and H 2 (g) 14. Which is least important in determining the physical behavior of a gas? (A) volume (B) pressure (C) temperature (D) chemical composition
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